What Happens to Bitcoin After All 21 Million Are Mined?

Bitcoin Hashrate, Difficulty and Tx Output Values Reach All Time Highs

Bitcoin Hashrate, Difficulty and Tx Output Values Reach All Time Highs submitted by crykenews to Bitcoin [link] [comments]

Addresses sending funds to themselves cause total output value for Bitcoin to skyrocket

Addresses sending funds to themselves cause total output value for Bitcoin to skyrocket submitted by cryptolobe to cryptolobe [link] [comments]

Addresses sending funds to themselves cause total output value for Bitcoin to skyrocket

Addresses sending funds to themselves cause total output value for Bitcoin to skyrocket submitted by n4bb to CoinPath [link] [comments]

How to search the blockchain for transactions with specific output value? /r/Bitcoin

How to search the blockchain for transactions with specific output value? /Bitcoin submitted by ABitcoinAllBot to BitcoinAll [link] [comments]

Jameson Lopp: "Bitcoin unspent transaction output breakdown by value and total bytes. H/T @pwuille"

Jameson Lopp: submitted by Egon_1 to btc [link] [comments]

Brief Analysis of Low Value (<100 satoshi) outputs and it's ROI for miners. /r/Bitcoin

Brief Analysis of Low Value (<100 satoshi) outputs and it's ROI for miners. /Bitcoin submitted by BitcoinAllBot to BitcoinAll [link] [comments]

Jameson Lopp: "Bitcoin unspent transaction output breakdown by value and total bytes. H/T @pwuille"

Jameson Lopp: submitted by BitcoinAllBot to BitcoinAll [link] [comments]

Jameson Lopp: "Bitcoin unspent transaction output breakdown by value and total bytes. H/T @pwuille" /r/btc

Jameson Lopp: submitted by BitcoinAllBot to BitcoinAll [link] [comments]

Bitcoin Farming, Basic Arithmetic, and you

I have written this guide to dispel a common misconception I hear from this community - that putting more than one Graphics Card in your Bitcoin Farm is a great idea.
TLDR: The FIRST graphics card you put in your bitcoin farm generates a bitcoin every 20 hours. Every additional graphics card you put in your bitcoin farm generates a bitcoin every 333.33 hours. This information is misstated on the wiki and in many videos I've seen.
More Complicated Maths TLDR from u/Mekhazzio :
TLDR: The bitcoin farm has a base production rate that's much higher than the rate added by each additional graphics cards. So when investing, you shouldn't be looking at how fast the whole farm pays itself off, but how much time it takes your N>1 graphics cards to each pay for themselves, because otherwise you could have just been pocketing the pure profit from the base production rate the whole time.
At current therapist/flea-FiR values:
That is to say, adding a GPU to an already-running farm takes three weeks before you've stopped losing money on that GPU.

A pretty simple formula is utilized to determine Bitcoin Farming output. The payback period for your first graphics card is around 3 days. For each additional graphics card that you put in the payback period is over 20 days. The reason that this has confused so many people is that they credit the production from Graphics Card 1 to the payback period for the rest of the Graphics Cards.
Caveat 1: Escape from Tarkov is a video game and, at least for us players, not a business. Many video game players are completionists, and I will not begrudge anyone who wants to max out every single part of their hideout because it will feel like an achievement. This guide discusses the impact of bitcoin farming on your PMC's wallet. If you find utility in maxing out the bitcoin farm for the feeling of completion then you should do it and probably just close this guide and not worry about it.
Caveat 2: This guide will not address people who hatchet run or pistol run to put graphics cards in their secure container that will usually end up being non-FIR. There are too many variables (spawn rate, survival rate, replacement value of just doing normal Tarkov raids instead of hatchet runs) to do a decent analysis. If you end up with non-FIR graphics cards you should put them in your Bitcoin Farm.
Analysis:
The formula for bitcoin generation is as follows:
Let's simplify some unnecessary constants and make this look more like a normal mathematical function. All we have to do is multiply (1/49) * (0.15) to get this, which is equivalent and much easier to understand:
Now, let's get some ground rules for investment:
Caveat 3: Prices may change, blah blah blah, unless the IRL bitcoin market crashes the conclusions from this guide will still be accurate for the most part.
I will also note that I'm not going to include the cost for fuel needed for production. Because you can craft expeditionary fuel into mag boxes, as well as do other crafts on your workbench and med station while you have the power on, this cost is negligible. Furthermore, since my thesis is that putting more graphics cards in is not worth it, the fact is that I can prove this mathematically without even accounting for the entire cost category of fuel only strengthens my argument.
Using these assumed prices, let's take a look at some different cases.
Case 1:
Building a Bitcoin Generator and putting a single graphics card in.
To calculate cost, we add the cost of building the empty generator (300k) to the single graphics card (250k) to get 550k rouble investment.
Lets calculate revenue using our formula before:BTC Generated per Hour = 0.05 + 0.003 * (Graphics Cards - 1)BTC Generated per Hour = 0.05 + 0.003 * (1 Graphics Cards - 1)BTC Generated per Hour = 0.05 + 0.003 * (0)BTC Generated per Hour = 0.05
So we're generating 5% of a bitcoin every hour which means we'll get a bitcoin from our farm every 20 hours.
So, every 20 hours we are generating a product worth ~150k. Since we invested ~550k we need to sell:
550k investment / 150k roubles per bitcoin = 3.66 physical bitcoins in order to recoup our investment
Since we can't harvest bitcoins until they are full, we actually need to wait until we get 4 bitcoins at which point we'll be making a slight profit. Generating 4 bitcoins will take 4 bitcoins * 20 hours per bitcoin = 80 hours or a little more than 3 days.
Case 2:
Adding a second graphics card to our bitcoin farm.
Now, as discussed above I'm not worried about non-FIR graphics cards that you hatchet ran to find. If you have an FIR graphics card then you can sell it on the flea market for the 250k price that I'm using as an assumption above.
This concept is called opportunity cost and if you don't understand it I will troll you in the comments: Putting an FIR graphics card into your bitcoin farm is the same as purchasing one off of the flea market and putting it in your bitcoin farm because you had the opportunity to just sell your FIR graphics card for the same price that you can buy it.
With that out of the way, let's do some math on our 2 graphics card bitcoin farm:
BTC Generated per Hour = 0.05 + 0.003 * (Graphics Cards - 1)BTC Generated per Hour = 0.05 + 0.003 * (2 Graphics Cards - 1)BTC Generated per Hour = 0.05 + 0.003 * 1BTC Generated per Hour = 0.053
So, for the cost of 250k roubles we have increased our bitcoin per hour generation by 0.003.
The first graphics card that we added to our bitcoin farm generates us one bitcoin every 20 hours, as discussed above.
The second graphics card that we added to our bitcoin farm generates 0.003 bitcoins per hour. To calculate how many hours this takes to get 1 bitcoin we do the math of 1 / 0.003 = 333.33 hours. 333.33 hours / 24 hours per day is 13.88 or roughly 14 days.
In order to recoup our investment from the 250k roubles we used to get our second graphics card we divide 250k roubles invested by 150k roubles per bitcoin = 1.66 bitcoins. We generate one bitcoin every 14 days, so we can multiply 14 days * 1.66 bitcoins = 23 days.
This math will hold true for every additional graphics card because the function is linear.
Thus, the payback period for your 250k investment in adding a graphics card past the first one to your bitcoin farm is 23 days.
To reiterate: The FIRST graphics card you put in your bitcoin farm generates a bitcoin every 20 hours. Every additional graphics card you put in your bitcoin farm generates a bitcoin every 333.33 hours.
submitted by Death4Chairman20x70 to EscapefromTarkov [link] [comments]

Power of the Command Line (bitcoin-cli, hwi, electrum, trezorctl)

I think some of the console tools available with HW wallets today are greatly under utilized. Here's a quick write-up on how to create and sign a TXN very similar to 43d27...1fc06 found on the SLIP-14 wallet. I'll be using TrezorCTL, Electrum, and HWI for the signing. I won't go much into the setup or install, but feel free to ask if you have questions about it. Note, you don't have to use all three of these. Any one will produce a valid signed TXN for broadcast. I just showed how to do it three ways. Whats more some of the Electrum and HWI steps are interchangeable.
ColdCard also has a utility called ckcc that will do the sign operation instead of HWI, but in many ways they are interchangeable. KeepKey and Ledger both have libraries for scripted signing but no one-shot, one-line console apps that I know of. But HWI and Electrum of course work on all four.

TrezorCTL

This is the what most would think of to use to craft and sign TXNs, and is definitely very simple. The signing uses a script called build_tx.py to create a JSON file that is then used by the btc sign-tx command. The whole process is basically:
  1. tools/build_tx.py | trezorctl btc sign-tx -
This just means, take the output of build_tx and sign it. To copy 43d27...1fc06, I wrote a small script to feed build_tx, so my process looks like:
  1. ~/input.sh | tools/build_tx.py | trezorctl btc sign-tx -
But it's all very simple. Note... I used TrezorCTL v0.12.2 but build_tx.py version 0.13.0 1.

input.sh

```

!/bin/bash

secho() { sleep 1; echo $*}
secho "Testnet" # coin name secho "tbtc1.trezor.io" # blockbook server and outpoint (below) secho "e294c4c172c3d87991b0369e45d6af8584be92914d01e3060fad1ed31d12ff00:0" secho "m/84'/1'/0'/0/0" # prev_out derivation to signing key secho "4294967293" # Sequence for RBF; hex(-3) secho "segwit" # Signature type on prev_out to use secho "" # NACK to progress to outs secho "2MsiAgG5LVDmnmJUPnYaCeQnARWGbGSVnr3" # out[0].addr secho "10000000" # out[1].amt secho "tb1q9l0rk0gkgn73d0gc57qn3t3cwvucaj3h8wtrlu" # out[1].addr secho "20000000" # out[1].amt secho "tb1qejqxwzfld7zr6mf7ygqy5s5se5xq7vmt96jk9x" # out[2].addr secho "99999694" # out[2].amt secho "" # NACK to progress to change secho "" # NACK to skip change secho "2" # txn.version secho "0" # txn.locktime ```

Electrum

Electrum is one of the better GUI wallets available, but it also has a pretty good console interface. Like before you need your Trezor with the SLIP-14 wallet loaded and paired to Electrum. I'll assume Electrum is up and running with the Trezor wallet loaded to make things simple.
Like with TrezorCTL, Electrum feeds on a JSON file, but unlike TrezorCTL it needs that JSON squished into the command line. This is a simple sed command, but I won't bore you with the details, but just assume that's done. So the process in Electrum (v4.0.3) looks like:
  1. electrum serialize (create psbt to sign)
  2. electrum --wallet signtransaction (sign said psbt)
Still pretty simple right! Below is the JSON I smushed for #1

txn.json

{ "inputs": [{ "prevout_hash":"e294c4c172c3d87991b0369e45d6af8584be92914d01e3060fad1ed31d12ff00", "prevout_n": 0, "value_sats": 129999867 }], "outputs": [{ "address": "2MsiAgG5LVDmnmJUPnYaCeQnARWGbGSVnr3", "value_sats": 10000000 },{ "address": "tb1q9l0rk0gkgn73d0gc57qn3t3cwvucaj3h8wtrlu", "value_sats": 20000000 },{ "address": "tb1qejqxwzfld7zr6mf7ygqy5s5se5xq7vmt96jk9x", "value_sats": 99999694 }]}

HWI

HWI is an unsung hero in my book. It's a very small clean and simple interface between HW wallets and Bitcoin Core. It currently supports a good range of HW wallets. It keeps itself narrowly focused on TXN signing and offloads most everything else to Bitcoin Core. Again, I'll assume you've imported your Trezor keypool into Core and done the requisite IBD and rescan. And if you don't have the RPC enabled, you can always clone these commands into the QT-console.
To sign our TXN in HWI (v1.1.2), we will first need to craft (and finalize) it in Bitcoin Core (0.21.1). Like in Electrum, we will have to use simple sed to smush some JSON into command arguments, but I'll assume you have that covered. It will take an inputs.json and an outputs.json named separately.
  1. bitcoin-cli createpsbt (create psbt)
  2. bitcoin-cli -rpcwallet= walletprocesspsbt (process psbt)
  3. hwi -f signtx (sign psbt)
  4. bitcoin-cli -rpcwallet= finalizepsbt (get a signed TXN from psbt)
A little more involved, but still nothing too bad. Plus this gives you the full power of Bitcoin Core including integrations with LND (lightning).

inputs.json

[{ "txid": "e294c4c172c3d87991b0369e45d6af8584be92914d01e3060fad1ed31d12ff00", "vout": 0 }]

outputs.json

[{ "2MsiAgG5LVDmnmJUPnYaCeQnARWGbGSVnr3": 0.10000000 },{ "tb1q9l0rk0gkgn73d0gc57qn3t3cwvucaj3h8wtrlu": 0.20000000 },{ "tb1qejqxwzfld7zr6mf7ygqy5s5se5xq7vmt96jk9x": 0.99999694 }]

Conclusion

This may all seem like very low level coding, but is surprisingly simple once you get a knack for it. Whats more, all these platforms support testnet which allows you to practice with valueless coins until you get the hang of it. And, like many things in bitcoin, this is all (mostly) python, which is one of the easier languages to learn.
Enjoy
Footnotes
1 - https://github.com/trezotrezor-firmware/issues/1296
submitted by brianddk to Bitcoin [link] [comments]

Gridcoin 5.0.0.0-Mandatory "Fern" Release

https://github.com/gridcoin-community/Gridcoin-Research/releases/tag/5.0.0.0
Finally! After over ten months of development and testing, "Fern" has arrived! This is a whopper. 240 pull requests merged. Essentially a complete rewrite that was started with the scraper (the "neural net" rewrite) in "Denise" has now been completed. Practically the ENTIRE Gridcoin specific codebase resting on top of the vanilla Bitcoin/Peercoin/Blackcoin vanilla PoS code has been rewritten. This removes the team requirement at last (see below), although there are many other important improvements besides that.
Fern was a monumental undertaking. We had to encode all of the old rules active for the v10 block protocol in new code and ensure that the new code was 100% compatible. This had to be done in such a way as to clear out all of the old spaghetti and ring-fence it with tightly controlled class implementations. We then wrote an entirely new, simplified ruleset for research rewards and reengineered contracts (which includes beacon management, polls, and voting) using properly classed code. The fundamentals of Gridcoin with this release are now on a very sound and maintainable footing, and the developers believe the codebase as updated here will serve as the fundamental basis for Gridcoin's future roadmap.
We have been testing this for MONTHS on testnet in various stages. The v10 (legacy) compatibility code has been running on testnet continuously as it was developed to ensure compatibility with existing nodes. During the last few months, we have done two private testnet forks and then the full public testnet testing for v11 code (the new protocol which is what Fern implements). The developers have also been running non-staking "sentinel" nodes on mainnet with this code to verify that the consensus rules are problem-free for the legacy compatibility code on the broader mainnet. We believe this amount of testing is going to result in a smooth rollout.
Given the amount of changes in Fern, I am presenting TWO changelogs below. One is high level, which summarizes the most significant changes in the protocol. The second changelog is the detailed one in the usual format, and gives you an inkling of the size of this release.

Highlights

Protocol

Note that the protocol changes will not become active until we cross the hard-fork transition height to v11, which has been set at 2053000. Given current average block spacing, this should happen around October 4, about one month from now.
Note that to get all of the beacons in the network on the new protocol, we are requiring ALL beacons to be validated. A two week (14 day) grace period is provided by the code, starting at the time of the transition height, for people currently holding a beacon to validate the beacon and prevent it from expiring. That means that EVERY CRUNCHER must advertise and validate their beacon AFTER the v11 transition (around Oct 4th) and BEFORE October 18th (or more precisely, 14 days from the actual date of the v11 transition). If you do not advertise and validate your beacon by this time, your beacon will expire and you will stop earning research rewards until you advertise and validate a new beacon. This process has been made much easier by a brand new beacon "wizard" that helps manage beacon advertisements and renewals. Once a beacon has been validated and is a v11 protocol beacon, the normal 180 day expiration rules apply. Note, however, that the 180 day expiration on research rewards has been removed with the Fern update. This means that while your beacon might expire after 180 days, your earned research rewards will be retained and can be claimed by advertising a beacon with the same CPID and going through the validation process again. In other words, you do not lose any earned research rewards if you do not stake a block within 180 days and keep your beacon up-to-date.
The transition height is also when the team requirement will be relaxed for the network.

GUI

Besides the beacon wizard, there are a number of improvements to the GUI, including new UI transaction types (and icons) for staking the superblock, sidestake sends, beacon advertisement, voting, poll creation, and transactions with a message. The main screen has been revamped with a better summary section, and better status icons. Several changes under the hood have improved GUI performance. And finally, the diagnostics have been revamped.

Blockchain

The wallet sync speed has been DRASTICALLY improved. A decent machine with a good network connection should be able to sync the entire mainnet blockchain in less than 4 hours. A fast machine with a really fast network connection and a good SSD can do it in about 2.5 hours. One of our goals was to reduce or eliminate the reliance on snapshots for mainnet, and I think we have accomplished that goal with the new sync speed. We have also streamlined the in-memory structures for the blockchain which shaves some memory use.
There are so many goodies here it is hard to summarize them all.
I would like to thank all of the contributors to this release, but especially thank @cyrossignol, whose incredible contributions formed the backbone of this release. I would also like to pay special thanks to @barton2526, @caraka, and @Quezacoatl1, who tirelessly helped during the testing and polishing phase on testnet with testing and repeated builds for all architectures.
The developers are proud to present this release to the community and we believe this represents the starting point for a true renaissance for Gridcoin!

Summary Changelog

Accrual

Changed

Most significantly, nodes calculate research rewards directly from the magnitudes in EACH superblock between stakes instead of using a two- or three- point average based on a CPID's current magnitude and the magnitude for the CPID when it last staked. For those long-timers in the community, this has been referred to as "Superblock Windows," and was first done in proof-of-concept form by @denravonska.

Removed

Beacons

Added

Changed

Removed

Unaltered

As a reminder:

Superblocks

Added

Changed

Removed

Voting

Added

Changed

Removed

Detailed Changelog

[5.0.0.0] 2020-09-03, mandatory, "Fern"

Added

Changed

Removed

Fixed

submitted by jamescowens to gridcoin [link] [comments]

Ledger Live adds Coin control: Here's why that matters.

Ledger Live adds Coin control: Here's why that matters.
Ledger Live version 2.11.1 (download link) adds Coin control for power users.
The coin control feature gives advanced users more granular control over their wallets. It enables them to change how and which coins are selected when making transactions. This increases their ability to manage their privacy and the network fees they will have to pay to spend their account balance.
More control over your coins

How does it work?

The account balance for Bitcoin and its derivatives consists of all the unspent transaction outputs (UTXOs) in the account. You can think of UTXOs as the coins in a regular wallet. When you receive money, you collect coins in your wallet. Then, when you want to make a payment, you get to choose which coins you pick from your wallet. Do you pick the largest coins first? Or do you want to spend all the smaller value coins to lighten up your wallet? Similar considerations can be made when creating a Bitcoin or Bitcoin derivative (altcoin) transaction.
Before the Coin Control feature was released, all transactions involving Bitcoin (and altcoins) automatically selected their coins using the First-In-First-Out (FIFO) algorithm. This strategy includes the oldest coin in the account, and when the amount is not sufficient the second-oldest coin is added, and so forth.
As of Ledger Live version 2.11.1, users are able to make use of a dedicated Coin Control tool to choose the coin selection strategy and the coins that may be spent.

Using Coin control in Ledger Live

Coin control is available in Advanced options in the Send flow
  1. Click on Send, choose an account to debit, and enter a recipient address. Click on Continue.
  2. Enter an amount and click on Advanced options. You will then see: - The currently selected, default coin selection strategy: Oldest coins first (FIFO). - A toggle to enable Replace-By-Fee (RBF). - A toggle to include coins from unconfirmed, replaceable transactions.
  3. Click on Coin control. The coin control modal opens.
  4. Select a Coin selection strategy from the dropdown menu: - Oldest coins first (FIFO). This is the default strategy that spends the oldest coins first. - Minimize fees (optimize size). This strategy tries to minimize the byte size of the transaction by spending the lowest number of UTXOs. This results in a low network fee. - Minimize future fees (merge coins), This strategy includes the maximum number of inputs so that a potential future price rise does not make smaller UTXOs economically unspendable. If the price of a crypto asset increases too much, small UTXOs may become worth less than the cost of the network fees to spend them.
  5. Select which coins may not be included in the selection by unticking their checkbox. The SELECTED indicator shows which coins will be included in the transaction. By changing the selection strategy and/or coins to include, the user has precise control over which coins end up being spent. The Coins to spend and Change to return indicators show how much is spent from and returned to the account.
  6. Click on Done to return to the Send flow to verify and send the transaction.
The coin control window lets you select the strategy as well as pick the coins. Coins marked SELECTED will be included in the transaction.

Coin status

The following statuses can be displayed for a coin:
  • Coins received in a transaction with 0 confirmations without RBF enabled: PENDING
  • Coins received in a transaction with 0 confirmations with RBF enabled: REPLACEABLE
  • Coins received in a transaction with 1337 confirmations: 1337 CONFIRMATIONS
By enabling the toggle Include coins from unconfirmed, replaceable transactions, replaceable transactions can be selected in the Coin control screen.

The Privacy use case

One of the main use cases for Coin control is to protect one’s privacy. UTXOs are, unfortunately, not perfectly fungible due to their unique history on the blockchain. Therefore, users may want to spend coins from different sources without mixing them together, because this would indicate to an outside observer of the blockchain that these addresses belong to the same account. For instance, if one were to spend coins bought on a KYC exchange, which are associated with the user’s identity, together with coins bought anonymously using cash, the anonymous coins could be linked to the user’s identity.
Another example would be that you would like to prevent spending a high-value coin for smaller purchases because this would unnecessarily show the person you’re paying how much you have. This is similar to not showing the boulanger how much is on your bank account when buying a baguette.

Let us know what you think!

We are excited to release this new feature because we think it will fulfill real needs of an important part of our users. This version of Ledger Live marks an important milestone, but we will continue working on more features that our community wants.
So, we invite you to try out Coin control in Ledger Live and let us know what you think! All feedback is welcome on this thread, on ledgerwallet, and you can send suggestions or get help through our official contact form.
We'd like to close out by underlining our commitment to the Bitcoin community, and our willingness to build the best wallet ecosystem for newbies as well as for power users.
submitted by fabnormal to Bitcoin [link] [comments]

Dragonchain Great Reddit Scaling Bake-Off Public Proposal

Dragonchain Great Reddit Scaling Bake-Off Public Proposal

Dragonchain Public Proposal TL;DR:

Dragonchain has demonstrated twice Reddit’s entire total daily volume (votes, comments, and posts per Reddit 2019 Year in Review) in a 24-hour demo on an operational network. Every single transaction on Dragonchain is decentralized immediately through 5 levels of Dragon Net, and then secured with combined proof on Bitcoin, Ethereum, Ethereum Classic, and Binance Chain, via Interchain. At the time, in January 2020, the entire cost of the demo was approximately $25K on a single system (transaction fees locked at $0.0001/txn). With current fees (lowest fee $0.0000025/txn), this would cost as little as $625.
Watch Joe walk through the entire proposal and answer questions on YouTube.
This proposal is also available on the Dragonchain blog.

Hello Reddit and Ethereum community!

I’m Joe Roets, Founder & CEO of Dragonchain. When the team and I first heard about The Great Reddit Scaling Bake-Off we were intrigued. We believe we have the solutions Reddit seeks for its community points system and we have them at scale.
For your consideration, we have submitted our proposal below. The team at Dragonchain and I welcome and look forward to your technical questions, philosophical feedback, and fair criticism, to build a scaling solution for Reddit that will empower its users. Because our architecture is unlike other blockchain platforms out there today, we expect to receive many questions while people try to grasp our project. I will answer all questions here in this thread on Reddit, and I've answered some questions in the stream on YouTube.
We have seen good discussions so far in the competition. We hope that Reddit’s scaling solution will emerge from The Great Reddit Scaling Bake-Off and that Reddit will have great success with the implementation.

Executive summary

Dragonchain is a robust open source hybrid blockchain platform that has proven to withstand the passing of time since our inception in 2014. We have continued to evolve to harness the scalability of private nodes, yet take full advantage of the security of public decentralized networks, like Ethereum. We have a live, operational, and fully functional Interchain network integrating Bitcoin, Ethereum, Ethereum Classic, and ~700 independent Dragonchain nodes. Every transaction is secured to Ethereum, Bitcoin, and Ethereum Classic. Transactions are immediately usable on chain, and the first decentralization is seen within 20 seconds on Dragon Net. Security increases further to public networks ETH, BTC, and ETC within 10 minutes to 2 hours. Smart contracts can be written in any executable language, offering full freedom to existing developers. We invite any developer to watch the demo, play with our SDK’s, review open source code, and to help us move forward. Dragonchain specializes in scalable loyalty & rewards solutions and has built a decentralized social network on chain, with very affordable transaction costs. This experience can be combined with the insights Reddit and the Ethereum community have gained in the past couple of months to roll out the solution at a rapid pace.

Response and PoC

In The Great Reddit Scaling Bake-Off post, Reddit has asked for a series of demonstrations, requirements, and other considerations. In this section, we will attempt to answer all of these requests.

Live Demo

A live proof of concept showing hundreds of thousands of transactions
On Jan 7, 2020, Dragonchain hosted a 24-hour live demonstration during which a quarter of a billion (250 million+) transactions executed fully on an operational network. Every single transaction on Dragonchain is decentralized immediately through 5 levels of Dragon Net, and then secured with combined proof on Bitcoin, Ethereum, Ethereum Classic, and Binance Chain, via Interchain. This means that every single transaction is secured by, and traceable to these networks. An attack on this system would require a simultaneous attack on all of the Interchained networks.
24 hours in 4 minutes (YouTube):
24 hours in 4 minutes
The demonstration was of a single business system, and any user is able to scale this further, by running multiple systems simultaneously. Our goals for the event were to demonstrate a consistent capacity greater than that of Visa over an extended time period.
Tooling to reproduce our demo is available here:
https://github.com/dragonchain/spirit-bomb

Source Code

Source code (for on & off-chain components as well tooling used for the PoC). The source code does not have to be shared publicly, but if Reddit decides to use a particular solution it will need to be shared with Reddit at some point.

Scaling

How it works & scales

Architectural Scaling

Dragonchain’s architecture attacks the scalability issue from multiple angles. Dragonchain is a hybrid blockchain platform, wherein every transaction is protected on a business node to the requirements of that business or purpose. A business node may be held completely private or may be exposed or replicated to any level of exposure desired.
Every node has its own blockchain and is independently scalable. Dragonchain established Context Based Verification as its consensus model. Every transaction is immediately usable on a trust basis, and in time is provable to an increasing level of decentralized consensus. A transaction will have a level of decentralization to independently owned and deployed Dragonchain nodes (~700 nodes) within seconds, and full decentralization to BTC and ETH within minutes or hours. Level 5 nodes (Interchain nodes) function to secure all transactions to public or otherwise external chains such as Bitcoin and Ethereum. These nodes scale the system by aggregating multiple blocks into a single Interchain transaction on a cadence. This timing is configurable based upon average fees for each respective chain. For detailed information about Dragonchain’s architecture, and Context Based Verification, please refer to the Dragonchain Architecture Document.

Economic Scaling

An interesting feature of Dragonchain’s network consensus is its economics and scarcity model. Since Dragon Net nodes (L2-L4) are independent staking nodes, deployment to cloud platforms would allow any of these nodes to scale to take on a large percentage of the verification work. This is great for scalability, but not good for the economy, because there is no scarcity, and pricing would develop a downward spiral and result in fewer verification nodes. For this reason, Dragonchain uses TIME as scarcity.
TIME is calculated as the number of Dragons held, multiplied by the number of days held. TIME influences the user’s access to features within the Dragonchain ecosystem. It takes into account both the Dragon balance and length of time each Dragon is held. TIME is staked by users against every verification node and dictates how much of the transaction fees are awarded to each participating node for every block.
TIME also dictates the transaction fee itself for the business node. TIME is staked against a business node to set a deterministic transaction fee level (see transaction fee table below in Cost section). This is very interesting in a discussion about scaling because it guarantees independence for business implementation. No matter how much traffic appears on the entire network, a business is guaranteed to not see an increased transaction fee rate.

Scaled Deployment

Dragonchain uses Docker and Kubernetes to allow the use of best practices traditional system scaling. Dragonchain offers managed nodes with an easy to use web based console interface. The user may also deploy a Dragonchain node within their own datacenter or favorite cloud platform. Users have deployed Dragonchain nodes on-prem on Amazon AWS, Google Cloud, MS Azure, and other hosting platforms around the world. Any executable code, anything you can write, can be written into a smart contract. This flexibility is what allows us to say that developers with no blockchain experience can use any code language to access the benefits of blockchain. Customers have used NodeJS, Python, Java, and even BASH shell script to write smart contracts on Dragonchain.
With Docker containers, we achieve better separation of concerns, faster deployment, higher reliability, and lower response times.
We chose Kubernetes for its self-healing features, ability to run multiple services on one server, and its large and thriving development community. It is resilient, scalable, and automated. OpenFaaS allows us to package smart contracts as Docker images for easy deployment.
Contract deployment time is now bounded only by the size of the Docker image being deployed but remains fast even for reasonably large images. We also take advantage of Docker’s flexibility and its ability to support any language that can run on x86 architecture. Any image, public or private, can be run as a smart contract using Dragonchain.

Flexibility in Scaling

Dragonchain’s architecture considers interoperability and integration as key features. From inception, we had a goal to increase adoption via integration with real business use cases and traditional systems.
We envision the ability for Reddit, in the future, to be able to integrate alternate content storage platforms or other financial services along with the token.
  • LBRY - To allow users to deploy content natively to LBRY
  • MakerDAO to allow users to lend small amounts backed by their Reddit community points.
  • STORJ/SIA to allow decentralized on chain storage of portions of content. These integrations or any other are relatively easy to integrate on Dragonchain with an Interchain implementation.

Cost

Cost estimates (on-chain and off-chain) For the purpose of this proposal, we assume that all transactions are on chain (posts, replies, and votes).
On the Dragonchain network, transaction costs are deterministic/predictable. By staking TIME on the business node (as described above) Reddit can reduce transaction costs to as low as $0.0000025 per transaction.
Dragonchain Fees Table

Getting Started

How to run it
Building on Dragonchain is simple and requires no blockchain experience. Spin up a business node (L1) in our managed environment (AWS), run it in your own cloud environment, or on-prem in your own datacenter. Clear documentation will walk you through the steps of spinning up your first Dragonchain Level 1 Business node.
Getting started is easy...
  1. Download Dragonchain’s dctl
  2. Input three commands into a terminal
  3. Build an image
  4. Run it
More information can be found in our Get started documents.

Architecture
Dragonchain is an open source hybrid platform. Through Dragon Net, each chain combines the power of a public blockchain (like Ethereum) with the privacy of a private blockchain.
Dragonchain organizes its network into five separate levels. A Level 1, or business node, is a totally private blockchain only accessible through the use of public/private keypairs. All business logic, including smart contracts, can be executed on this node directly and added to the chain.
After creating a block, the Level 1 business node broadcasts a version stripped of sensitive private data to Dragon Net. Three Level 2 Validating nodes validate the transaction based on guidelines determined from the business. A Level 3 Diversity node checks that the level 2 nodes are from a diverse array of locations. A Level 4 Notary node, hosted by a KYC partner, then signs the validation record received from the Level 3 node. The transaction hash is ledgered to the Level 5 public chain to take advantage of the hash power of massive public networks.
Dragon Net can be thought of as a “blockchain of blockchains”, where every level is a complete private blockchain. Because an L1 can send to multiple nodes on a single level, proof of existence is distributed among many places in the network. Eventually, proof of existence reaches level 5 and is published on a public network.

API Documentation

APIs (on chain & off)

SDK Source

Nobody’s Perfect

Known issues or tradeoffs
  • Dragonchain is open source and even though the platform is easy enough for developers to code in any language they are comfortable with, we do not have so large a developer community as Ethereum. We would like to see the Ethereum developer community (and any other communities) become familiar with our SDK’s, our solutions, and our platform, to unlock the full potential of our Ethereum Interchain. Long ago we decided to prioritize both Bitcoin and Ethereum Interchains. We envision an ecosystem that encompasses different projects to give developers the ability to take full advantage of all the opportunities blockchain offers to create decentralized solutions not only for Reddit but for all of our current platforms and systems. We believe that together we will take the adoption of blockchain further. We currently have additional Interchain with Ethereum Classic. We look forward to Interchain with other blockchains in the future. We invite all blockchains projects who believe in decentralization and security to Interchain with Dragonchain.
  • While we only have 700 nodes compared to 8,000 Ethereum and 10,000 Bitcoin nodes. We harness those 18,000 nodes to scale to extremely high levels of security. See Dragonchain metrics.
  • Some may consider the centralization of Dragonchain’s business nodes as an issue at first glance, however, the model is by design to protect business data. We do not consider this a drawback as these nodes can make any, none, or all data public. Depending upon the implementation, every subreddit could have control of its own business node, for potential business and enterprise offerings, bringing new alternative revenue streams to Reddit.

Costs and resources

Summary of cost & resource information for both on-chain & off-chain components used in the PoC, as well as cost & resource estimates for further scaling. If your PoC is not on mainnet, make note of any mainnet caveats (such as congestion issues).
Every transaction on the PoC system had a transaction fee of $0.0001 (one-hundredth of a cent USD). At 256MM transactions, the demo cost $25,600. With current operational fees, the same demonstration would cost $640 USD.
For the demonstration, to achieve throughput to mimic a worldwide payments network, we modeled several clients in AWS and 4-5 business nodes to handle the traffic. The business nodes were tuned to handle higher throughput by adjusting memory and machine footprint on AWS. This flexibility is valuable to implementing a system such as envisioned by Reddit. Given that Reddit’s daily traffic (posts, replies, and votes) is less than half that of our demo, we would expect that the entire Reddit system could be handled on 2-5 business nodes using right-sized containers on AWS or similar environments.
Verification was accomplished on the operational Dragon Net network with over 700 independently owned verification nodes running around the world at no cost to the business other than paid transaction fees.

Requirements

Scaling

This PoC should scale to the numbers below with minimal costs (both on & off-chain). There should also be a clear path to supporting hundreds of millions of users.
Over a 5 day period, your scaling PoC should be able to handle:
*100,000 point claims (minting & distributing points) *25,000 subscriptions *75,000 one-off points burning *100,000 transfers
During Dragonchain’s 24 hour demo, the above required numbers were reached within the first few minutes.
Reddit’s total activity is 9000% more than Ethereum’s total transaction level. Even if you do not include votes, it is still 700% more than Ethereum’s current volume. Dragonchain has demonstrated that it can handle 250 million transactions a day, and it’s architecture allows for multiple systems to work at that level simultaneously. In our PoC, we demonstrate double the full capacity of Reddit, and every transaction was proven all the way to Bitcoin and Ethereum.
Reddit Scaling on Ethereum

Decentralization

Solutions should not depend on any single third-party provider. We prefer solutions that do not depend on specific entities such as Reddit or another provider, and solutions with no single point of control or failure in off-chain components but recognize there are numerous trade-offs to consider
Dragonchain’s architecture calls for a hybrid approach. Private business nodes hold the sensitive data while the validation and verification of transactions for the business are decentralized within seconds and secured to public blockchains within 10 minutes to 2 hours. Nodes could potentially be controlled by owners of individual subreddits for more organic decentralization.
  • Billing is currently centralized - there is a path to federation and decentralization of a scaled billing solution.
  • Operational multi-cloud
  • Operational on-premises capabilities
  • Operational deployment to any datacenter
  • Over 700 independent Community Verification Nodes with proof of ownership
  • Operational Interchain (Interoperable to Bitcoin, Ethereum, and Ethereum Classic, open to more)

Usability Scaling solutions should have a simple end user experience.

Users shouldn't have to maintain any extra state/proofs, regularly monitor activity, keep track of extra keys, or sign anything other than their normal transactions
Dragonchain and its customers have demonstrated extraordinary usability as a feature in many applications, where users do not need to know that the system is backed by a live blockchain. Lyceum is one of these examples, where the progress of academy courses is being tracked, and successful completion of courses is rewarded with certificates on chain. Our @Save_The_Tweet bot is popular on Twitter. When used with one of the following hashtags - #please, #blockchain, #ThankYou, or #eternalize the tweet is saved through Eternal to multiple blockchains. A proof report is available for future reference. Other examples in use are DEN, our decentralized social media platform, and our console, where users can track their node rewards, view their TIME, and operate a business node.
Examples:

Transactions complete in a reasonable amount of time (seconds or minutes, not hours or days)
All transactions are immediately usable on chain by the system. A transaction begins the path to decentralization at the conclusion of a 5-second block when it gets distributed across 5 separate community run nodes. Full decentralization occurs within 10 minutes to 2 hours depending on which interchain (Bitcoin, Ethereum, or Ethereum Classic) the transaction hits first. Within approximately 2 hours, the combined hash power of all interchained blockchains secures the transaction.

Free to use for end users (no gas fees, or fixed/minimal fees that Reddit can pay on their behalf)
With transaction pricing as low as $0.0000025 per transaction, it may be considered reasonable for Reddit to cover transaction fees for users.
All of Reddit's Transactions on Blockchain (month)
Community points can be earned by users and distributed directly to their Reddit account in batch (as per Reddit minting plan), and allow users to withdraw rewards to their Ethereum wallet whenever they wish. Withdrawal fees can be paid by either user or Reddit. This model has been operating inside the Dragonchain system since 2018, and many security and financial compliance features can be optionally added. We feel that this capability greatly enhances user experience because it is seamless to a regular user without cryptocurrency experience, yet flexible to a tech savvy user. With regard to currency or token transactions, these would occur on the Reddit network, verified to BTC and ETH. These transactions would incur the $0.0000025 transaction fee. To estimate this fee we use the monthly active Reddit users statista with a 60% adoption rate and an estimated 10 transactions per month average resulting in an approximate $720 cost across the system. Reddit could feasibly incur all associated internal network charges (mining/minting, transfer, burn) as these are very low and controllable fees.
Reddit Internal Token Transaction Fees

Reddit Ethereum Token Transaction Fees
When we consider further the Ethereum fees that might be incurred, we have a few choices for a solution.
  1. Offload all Ethereum transaction fees (user withdrawals) to interested users as they wish to withdraw tokens for external use or sale.
  2. Cover Ethereum transaction fees by aggregating them on a timed schedule. Users would request withdrawal (from Reddit or individual subreddits), and they would be transacted on the Ethereum network every hour (or some other schedule).
  3. In a combination of the above, customers could cover aggregated fees.
  4. Integrate with alternate Ethereum roll up solutions or other proposals to aggregate minting and distribution transactions onto Ethereum.

Bonus Points

Users should be able to view their balances & transactions via a blockchain explorer-style interface
From interfaces for users who have no knowledge of blockchain technology to users who are well versed in blockchain terms such as those present in a typical block explorer, a system powered by Dragonchain has flexibility on how to provide balances and transaction data to users. Transactions can be made viewable in an Eternal Proof Report, which displays raw data along with TIME staking information and traceability all the way to Bitcoin, Ethereum, and every other Interchained network. The report shows fields such as transaction ID, timestamp, block ID, multiple verifications, and Interchain proof. See example here.
Node payouts within the Dragonchain console are listed in chronological order and can be further seen in either Dragons or USD. See example here.
In our social media platform, Dragon Den, users can see, in real-time, their NRG and MTR balances. See example here.
A new influencer app powered by Dragonchain, Raiinmaker, breaks down data into a user friendly interface that shows coin portfolio, redeemed rewards, and social scores per campaign. See example here.

Exiting is fast & simple
Withdrawing funds on Dragonchain’s console requires three clicks, however, withdrawal scenarios with more enhanced security features per Reddit’s discretion are obtainable.

Interoperability Compatibility with third party apps (wallets/contracts/etc) is necessary.
Proven interoperability at scale that surpasses the required specifications. Our entire platform consists of interoperable blockchains connected to each other and traditional systems. APIs are well documented. Third party permissions are possible with a simple smart contract without the end user being aware. No need to learn any specialized proprietary language. Any code base (not subsets) is usable within a Docker container. Interoperable with any blockchain or traditional APIs. We’ve witnessed relatively complex systems built by engineers with no blockchain or cryptocurrency experience. We’ve also demonstrated the creation of smart contracts within minutes built with BASH shell and Node.js. Please see our source code and API documentation.

Scaling solutions should be extensible and allow third parties to build on top of it Open source and extensible
APIs should be well documented and stable

Documentation should be clear and complete
For full documentation, explore our docs, SDK’s, Github repo’s, architecture documents, original Disney documentation, and other links or resources provided in this proposal.

Third-party permissionless integrations should be possible & straightforward Smart contracts are Docker based, can be written in any language, use full language (not subsets), and can therefore be integrated with any system including traditional system APIs. Simple is better. Learning an uncommon or proprietary language should not be necessary.
Advanced knowledge of mathematics, cryptography, or L2 scaling should not be required. Compatibility with common utilities & toolchains is expected.
Dragonchain business nodes and smart contracts leverage Docker to allow the use of literally any language or executable code. No proprietary language is necessary. We’ve witnessed relatively complex systems built by engineers with no blockchain or cryptocurrency experience. We’ve also demonstrated the creation of smart contracts within minutes built with BASH shell and Node.js.

Bonus

Bonus Points: Show us how it works. Do you have an idea for a cool new use case for Community Points? Build it!

TIME

Community points could be awarded to Reddit users based upon TIME too, whereas the longer someone is part of a subreddit, the more community points someone naturally gained, even if not actively commenting or sharing new posts. A daily login could be required for these community points to be credited. This grants awards to readers too and incentivizes readers to create an account on Reddit if they browse the website often. This concept could also be leveraged to provide some level of reputation based upon duration and consistency of contribution to a community subreddit.

Dragon Den

Dragonchain has already built a social media platform that harnesses community involvement. Dragon Den is a decentralized community built on the Dragonchain blockchain platform. Dragon Den is Dragonchain’s answer to fake news, trolling, and censorship. It incentivizes the creation and evaluation of quality content within communities. It could be described as being a shareholder of a subreddit or Reddit in its entirety. The more your subreddit is thriving, the more rewarding it will be. Den is currently in a public beta and in active development, though the real token economy is not live yet. There are different tokens for various purposes. Two tokens are Lair Ownership Rights (LOR) and Lair Ownership Tokens (LOT). LOT is a non-fungible token for ownership of a specific Lair. LOT will only be created and converted from LOR.
Energy (NRG) and Matter (MTR) work jointly. Your MTR determines how much NRG you receive in a 24-hour period. Providing quality content, or evaluating content will earn MTR.

Security. Users have full ownership & control of their points.
All community points awarded based upon any type of activity or gift, are secured and provable to all Interchain networks (currently BTC, ETH, ETC). Users are free to spend and withdraw their points as they please, depending on the features Reddit wants to bring into production.

Balances and transactions cannot be forged, manipulated, or blocked by Reddit or anyone else
Users can withdraw their balance to their ERC20 wallet, directly through Reddit. Reddit can cover the fees on their behalf, or the user covers this with a portion of their balance.

Users should own their points and be able to get on-chain ERC20 tokens without permission from anyone else
Through our console users can withdraw their ERC20 rewards. This can be achieved on Reddit too. Here is a walkthrough of our console, though this does not show the quick withdrawal functionality, a user can withdraw at any time. https://www.youtube.com/watch?v=aNlTMxnfVHw

Points should be recoverable to on-chain ERC20 tokens even if all third-parties involved go offline
If necessary, signed transactions from the Reddit system (e.g. Reddit + Subreddit) can be sent to the Ethereum smart contract for minting.

A public, third-party review attesting to the soundness of the design should be available
To our knowledge, at least two large corporations, including a top 3 accounting firm, have conducted positive reviews. These reviews have never been made public, as Dragonchain did not pay or contract for these studies to be released.

Bonus points
Public, third-party implementation review available or in progress
See above

Compatibility with HSMs & hardware wallets
For the purpose of this proposal, all tokenization would be on the Ethereum network using standard token contracts and as such, would be able to leverage all hardware wallet and Ethereum ecosystem services.

Other Considerations

Minting/distributing tokens is not performed by Reddit directly
This operation can be automated by smart contract on Ethereum. Subreddits can if desired have a role to play.

One off point burning, as well as recurring, non-interactive point burning (for subreddit memberships) should be possible and scalable
This is possible and scalable with interaction between Dragonchain Reddit system and Ethereum token contract(s).

Fully open-source solutions are strongly preferred
Dragonchain is fully open source (see section on Disney release after conclusion).

Conclusion

Whether it is today, or in the future, we would like to work together to bring secure flexibility to the highest standards. It is our hope to be considered by Ethereum, Reddit, and other integrative solutions so we may further discuss the possibilities of implementation. In our public demonstration, 256 million transactions were handled in our operational network on chain in 24 hours, for the low cost of $25K, which if run today would cost $625. Dragonchain’s interoperable foundation provides the atmosphere necessary to implement a frictionless community points system. Thank you for your consideration of our proposal. We look forward to working with the community to make something great!

Disney Releases Blockchain Platform as Open Source

The team at Disney created the Disney Private Blockchain Platform. The system was a hybrid interoperable blockchain platform for ledgering and smart contract development geared toward solving problems with blockchain adoption and usability. All objective evaluation would consider the team’s output a success. We released a list of use cases that we explored in some capacity at Disney, and our input on blockchain standardization as part of our participation in the W3C Blockchain Community Group.
https://lists.w3.org/Archives/Public/public-blockchain/2016May/0052.html

Open Source

In 2016, Roets proposed to release the platform as open source to spread the technology outside of Disney, as others within the W3C group were interested in the solutions that had been created inside of Disney.
Following a long process, step by step, the team met requirements for release. Among the requirements, the team had to:
  • Obtain VP support and approval for the release
  • Verify ownership of the software to be released
  • Verify that no proprietary content would be released
  • Convince the organization that there was a value to the open source community
  • Convince the organization that there was a value to Disney
  • Offer the plan for ongoing maintenance of the project outside of Disney
  • Itemize competing projects
  • Verify no conflict of interest
  • Preferred license
  • Change the project name to not use the name Disney, any Disney character, or any other associated IP - proposed Dragonchain - approved
  • Obtain legal approval
  • Approval from corporate, parks, and other business units
  • Approval from multiple Disney patent groups Copyright holder defined by Disney (Disney Connected and Advanced Technologies)
  • Trademark searches conducted for the selected name Dragonchain
  • Obtain IT security approval
  • Manual review of OSS components conducted
  • OWASP Dependency and Vulnerability Check Conducted
  • Obtain technical (software) approval
  • Offer management, process, and financial plans for the maintenance of the project.
  • Meet list of items to be addressed before release
  • Remove all Disney project references and scripts
  • Create a public distribution list for email communications
  • Remove Roets’ direct and internal contact information
  • Create public Slack channel and move from Disney slack channels
  • Create proper labels for issue tracking
  • Rename internal private Github repository
  • Add informative description to Github page
  • Expand README.md with more specific information
  • Add information beyond current “Blockchains are Magic”
  • Add getting started sections and info on cloning/forking the project
  • Add installation details
  • Add uninstall process
  • Add unit, functional, and integration test information
  • Detail how to contribute and get involved
  • Describe the git workflow that the project will use
  • Move to public, non-Disney git repository (Github or Bitbucket)
  • Obtain Disney Open Source Committee approval for release
On top of meeting the above criteria, as part of the process, the maintainer of the project had to receive the codebase on their own personal email and create accounts for maintenance (e.g. Github) with non-Disney accounts. Given the fact that the project spanned multiple business units, Roets was individually responsible for its ongoing maintenance. Because of this, he proposed in the open source application to create a non-profit organization to hold the IP and maintain the project. This was approved by Disney.
The Disney Open Source Committee approved the application known as OSSRELEASE-10, and the code was released on October 2, 2016. Disney decided to not issue a press release.
Original OSSRELASE-10 document

Dragonchain Foundation

The Dragonchain Foundation was created on January 17, 2017. https://den.social/l/Dragonchain/24130078352e485d96d2125082151cf0/dragonchain-and-disney/
submitted by j0j0r0 to ethereum [link] [comments]

Technical: Confidential Transactions and Their Implementation Tradeoffs

As requested by estradata here: https://old.reddit.com/Bitcoin/comments/iylou9/what_are_some_of_the_latest_innovations_in_the/g6heez1/
It is a general issue that crops up at the extremes of cryptography, with quantum breaks being just one of the extremes of (classical) cryptography.

Computational vs Information-Theoretic

The dichotomy is between computationally infeasible vs informationally-theoretic infeasible. Basically:
Quantum breaks represent a possible reduction in computational infeasibility of certain things, but not information-theoretic infeasibility.
For example, suppose you want to know what 256-bit preimages map to 256-bit hashes. In theory, you just need to build a table with 2256 entries and start from 0x0000000000000000000000000000000000000000000000000000000000000000 and so on. This is computationally infeasible, but not information-theoretic infeasible.
However, suppose you want to know what preimages, of any size, map to 256-bit hashes. Since the preimages can be of any size, after finishing with 256-bit preimages, you have to proceed to 257-bit preimages. And so on. And there is no size limit, so you will literally never finish. Even if you lived forever, you would not complete it. This is information-theoretic infeasible.

Commitments

How does this relate to confidential transactions? Basically, every confidential transaction simply hides the value behind a homomorphic commitment. What is a homomorphic commitment? Okay, let's start with commitments. A commitment is something which lets you hide something, and later reveal what you hid. Until you reveal it, even if somebody has access to the commitment, they cannot reverse it to find out what you hid. This is called the "hiding property" of commitments. However, when you do reveal it (or "open the commitment"), then you cannot replace what you hid with some other thing. This is called the "binding property" of commitments.
For example, a hash of a preimage is a commitment. Suppose I want to commit to something. For example, I want to show that I can predict the future using the energy of a spare galaxy I have in my pocket. I can hide that something by hashing a description of the future. Then I can give the hash to you. You still cannot learn the future, because it's just a hash, and you can't reverse the hash ("hiding"). But suppose the future event occurs. I can reveal that I did, in fact, know the future. So I give you the description, and you hash it and compare it to the hash I gave earlier. Because of preimage resistance, I cannot retroactively change what I hid in the hash, so what I gave must have been known to me at the time that I gave you the commitment i..e. hash ("binding").

Homomorphic Commitments

A homomorphic commitment simply means that if I can do certain operations on preimages of the commitment scheme, there are certain operations on the commitments that would create similar ("homo") changes ("morphic") to the commitments. For example, suppose I have a magical function h() which is a homomorphic commitment scheme. It can hide very large (near 256-bit) numbers. Then if h() is homomorphic, there may be certain operations on numbers behind the h() that have homomorphisms after the h(). For example, I might have an operation <+> that is homomorphic in h() on +, or in other words, if I have two large numbers a and b, then h(a + b) = h(a) <+> h(b). + and <+> are different operations, but they are homomorphic to each other.
For example, elliptic curve scalars and points have homomorphic operations. Scalars (private keys) are "just" very large near-256-bit numbers, while points are a scalar times a standard generator point G. Elliptic curve operations exist where there is a <+> between points that is homomorphic on standard + on scalars, and a <*> between a scalar and a point that is homomorphic on standard * multiplication on scalars.
For example, suppose I have two large scalars a and b. I can use elliptic curve points as a commitment scheme: I can take a <*> G to generate a point A. It is hiding since nobody can learn what a is unless I reveal it (a and A can be used in standard ECDSA private-public key cryptography, with the scalar a as the private key and the point A as the public key, and the a cannot be derived even if somebody else knows A). Thus, it is hiding. At the same time, for a particular point A and standard generator point G, there is only one possible scalar a which when "multiplied" with G yields A. So scalars and elliptic curve points are a commitment scheme, with both hiding and binding properties.
Now, as mentioned there is a <+> operation on points that is homomorphic to the + operation on corresponding scalars. For example, suppose there are two scalars a and b. I can compute (a + b) <*> G to generate a particular point. But even if I don't know scalars a and b, but I do know points A = a <*> G and B = b <*> G, then I can use A <+> B to derive (a + b) <*> G (or equivalently, (a <*> G) <+> (b <*> G) == (a + b) <*> G). This makes points a homomorphic commitment scheme on scalars.

Confidential Transactions: A Sketch

This is useful since we can easily use the near-256-bit scalars in SECP256K1 elliptic curves to easily represent values in a monetary system, and hide those values by using a homomorphic commitment scheme. We can use the hiding property to prevent people from learning the values of the money we are sending and receiving.
Now, in a proper cryptocurrency, a normal, non-coinbase transaction does not create or destroy coins: the values of the input coins are equal to the value of the output coins. We can use a homomorphic commitment scheme. Suppose I have a transaction that consumes an input value a and creates two output values b and c. That is, a = b + c, i.e. the sum of all inputs a equals the sum of all outputs b and c. But remember, with a homomorphic commitment scheme like elliptic curve points, there exists a <+> operation on points that is homomorphic to the ordinary school-arithmetic + addition on large numbers. So, confidential transactions can use points a <*> G as input, and points b <*> G and c <*> G as output, and we can easily prove that a <*> G = (b <*> G) <+> (c <*> G) if a = b + c, without revealing a, b, or c to anyone.

Pedersen Commitments

Actually, we cannot just use a <*> G as a commitment scheme in practice. Remember, Bitcoin has a cap on the number of satoshis ever to be created, and it's less than 253 satoshis, which is fairly trivial. I can easily compute all values of a <*> G for all values of a from 0 to 253 and know which a <*> G corresponds to which actual amount a. So in confidential transactions, we cannot naively use a <*> G commitments, we need Pedersen commitments.
If you know what a "salt" is, then Pedersen commitments are fairly obvious. A "salt" is something you add to e.g. a password so that the hash of the password is much harder to attack. Humans are idiots and when asked to generate passwords, will output a password that takes less than 230 possibilities, which is fairly easy to grind. So what you do is that you "salt" a password by prepending a random string to it. You then hash the random string + password, and store the random string --- the salt --- together with the hash in your database. Then when somebody logs in, you take the password, prepend the salt, hash, and check if the hash matches with the in-database hash, and you let them log in. Now, with a hash, even if somebody copies your password database, the can't get the password. They're hashed. But with a salt, even techniques like rainbow tables make a hacker's life even harder. They can't hash a possible password and check every hash in your db for something that matches. Instead, if they get a possible password, they have to prepend each salt, hash, then compare. That greatly increases the computational needs of a hacker, which is why salts are good.
What a Pedersen commitment is, is a point a <*> H, where a is the actual value you commit to, plus <+> another point r <*> G. H here is a second standard generator point, different from G. The r is the salt in the Pedersen commitment. It makes it so that even if you show (a <*> H) <+> (r <*> G) to somebody, they can't grind all possible values of a and try to match it with your point --- they also have to grind r (just as with the password-salt example above). And r is much larger, it can be a true near-256-bit number that is the range of scalars in SECP256K1, whereas a is constrained to "reasonable" numbers of satoshi, which cannot exceed 21 million Bitcoins.
Now, in order to validate a transaction with input a and outputs b and c, you only have to prove a = b + c. Suppose we are hiding those amounts using Pedersen commitments. You have an input of amount a, and you know a and r. The blockchain has an amount (a <*> H) <+> (r <*> G). In order to create the two outputs b and c, you just have to create two new r scalars such that r = r[0] + r[1]. This is trivial, you just select a new random r[0] and then compute r[1] = r - r[0], it's just basic algebra.
Then you create a transaction consuming the input (a <*> H) <+> (r <*> G) and outputs (b <*> H) <+> (r[0] <*> G) and (c <*> H) <+> (r[1] <*> G). You know that a = b + c, and r = r[0] + r[1], while fullnodes around the world, who don't know any of the amounts or scalars involved, can just take the points (a <*> H) <+> (r <*> G) and see if it equals (b <*> H) <+> (r[0] <*> G) <+> (c <*> H) <+> (r[1] <*> G). That is all that fullnodes have to validate, they just need to perform <+> operations on points and comparison on points, and from there they validate transactions, all without knowing the actual values involved.

Computational Binding, Information-Theoretic Hiding

Like all commitments, Pedersen Commitments are binding and hiding.
However, there are really two kinds of commitments:
What does this mean? It's just a measure of how "impossible" binding vs hiding is. Pedersen commitments are computationally binding, meaning that in theory, a user of this commitment with arbitrary time and space and energy can, in theory, replace the amount with something else. However, it is information-theoretic hiding, meaning an attacker with arbitrary time and space and energy cannot figure out exactly what got hidden behind the commitment.
But why?
Now, we have been using a and a <*> G as private keys and public keys in ECDSA and Schnorr. There is an operation <*> on a scalar and a point that generates another point, but we cannot "revrese" this operation. For example, even if I know A, and know that A = a <*> G, but do not know a, I cannot derive a --- there is no operation between A G that lets me know a.
Actually there is: I "just" need to have so much time, space, and energy that I just start counting a from 0 to 2256 and find which a results in A = a <*> G. This is a computational limit: I don't have a spare universe in my back pocket I can use to do all those computations.
Now, replace a with h and A with H. Remember that Pedersen commitments use a "second" standard generator point. The generator points G and H are "not really special" --- they are just random points on the curve that we selected and standardized. There is no operation H G such that I can learn h where H = h <*> G, though if I happen to have a spare universe in my back pocket I can "just" brute force it.
Suppose I do have a spare universe in my back pocket, and learn h = H G such that H = h <*> G. What can I do in Pedersen commitments?
Well, I have an amount a that is committed to by (a <*> H) <+> (r <*> G). But I happen to know h! Suppose I want to double my money a without involving Elon Musk. Then:
That is what we mean by computationally binding: if I can compute h such that H = h <*> G, then I can find another number which opens the same commitment. And of course I'd make sure that number is much larger than what I originally had in that address!
Now, the reason why it is "only" computationally binding is that it is information-theoretically hiding. Suppose somebody knows h, but has no money in the cryptocurrency. All they see are points. They can try to find what the original amounts are, but because any amount can be mapped to "the same" point with knowledge of h (e.g. in the above, a and 2 * a got mapped to the same point by "just" replacing the salt r with r - a * h; this can be done for 3 * a, 4 * a etc.), they cannot learn historical amounts --- the a in historical amounts could be anything.
The drawback, though, is that --- as seen above --- arbitrary inflation is now introduced once somebody knows h. They can multiply their money by any arbitrary factor with knowledge of h.
It is impossible to have both perfect hiding (i.e. historical amounts remain hidden even after a computational break) and perfect binding (i.e. you can't later open the commitment to a different, much larger, amount).
Pedersen commitments just happen to have perfect hiding, but only computationally-infeasible binding. This means they allow hiding historical values, but in case of anything that allows better computational power --- including but not limited to quantum breaks --- they allow arbitrary inflation.

Changing The Tradeoffs with ElGamal Commitments

An ElGamal commitment is just a Pedersen commitment, but with the point r <*> G also stored in a separate section of the transaction.
This commits the r, and fixes it to a specific value. This prevents me from opening my (a <*> H) <+> (r <*> G) as ((2 * a) <*> H) <+> ((r - a * h) <*> G), because the (r - a * h) would not match the r <*> G sitting in a separate section of the transaction. This forces me to be bound to that specific value, and no amount of computation power will let me escape --- it is information-theoretically binding i.e. perfectly binding.
But that is now computationally hiding. An evil surveillor with arbitrary time and space can focus on the r <*> G sitting in a separate section of the transaction, and grind r from 0 to 2256 to determine what r matches that point. Then from there, they can negate r to get (-r) <*> G and add it to the (a <*> H) <+> (r <*> G) to get a <*> H, and then grind that to determine the value a. With massive increases in computational ability --- including but not limited to quantum breaks --- an evil surveillor can see all the historical amounts of confidential transactions.

Conclusion

This is the source of the tradeoff: either you design confidential transactions so in case of a quantum break, historical transactions continue to hide their amounts, but inflation of the money is now unavoidable, OR you make the money supply sacrosanct, but you potentially sacrifice amount hiding in case of some break, including but not limited to quantum breaks.
submitted by almkglor to Bitcoin [link] [comments]

Paul Mampilly's Secret Portfolio Guesses?

I sat thru an hour plus long video expecting to get some new ticker symbols for Paul's secret portfolio. He said in his email that he would provide "an opportunity to get the names for the ticker symbols". I should've read that closer as that means he was not going to provide them without a catch. This is a subscription that Paul charges $5k for. While I am a subscriber to his "Profits Unlimited", and have been satisfied with the results so far, I couldn’t afford the subscription if I wanted to.
I took notes on the video and tried to get as much detail as I could (which is tough because he doesn't allow you to rewind or navigate the video in the interface he shows it on). I did research and think I found a couple, but I was hoping you guys confirm and potentially help identify any of these stocks that he personally invests in.
I tried to type up what I saw from some of these stocks…
Graphene stocks...
  1. Graphene can filter ocean water in a single use, stop rust with graphene infused paint, and can detect cancer in the human body. He mentions gains by G6, Talga Resources, and Tunghsu Optoelectronic (so it can be assumed it's not one of these). Paul predicts Graphene industry to be 13x it's size by 2027. The company he mentions is developing a graphene-based powder that can strengthen any substance. they are a mining company based in Australia. They are also developing a new graphene-powered battery which could charge a phone in 1-2 minutes and electric vehicles in 5. After researching, I believe this is FGPHF. Let me know if you think different.
  2. An offshoot of one of the largest industrial firms in Canada. Canada’s federal government is investing in it. A “tiny” company now that commissioned it’s first large-scale production facility with a production line that is 100% automated. This one I'm not sure of.
Blockchain Stocks...
  1. Blockchain stock. Soared 26,000% just for "adding blockchain to it’s name” and Paul thinks it will keep growing. I assume he is referring to the bitcoin boom in 2017. Paul states he thinks Bitcoin will hit $1mil in his lifetime. Not much detail here. Quick google search shows: Riot Blockchain, Hive Blockchain, and Long Blockchain Corp. One of these maybe?
  2. This stock is one of the leading crypto miners in the world and the company’s revenues grew 66% last year. Not much info here.
Global energy storage market…
  1. 13x growth by 2030. Paul likes an energy storage firm that is developing a new type of battery that can last 20-25 years minimum. Flow battery company with a current value of about $30 million. They’ve done a 180 and are putting everything into a niche corner of the battery market. Completed their first full battery system 2 years ago. Company plans to provide batteries for telecom towers and is expanding into China, New Zealand, and Australia.
  2. Company based out of France. A renewable powerhouse that owns over 100 power plants. Completed 7 renewable power plants last year and have another 10 in the works. Recently bought out another company operating 95 power plants and are expanding into Brazil, Mexico, Egypt, South Africa. Company has goal to increase energy output by 570% by 2023. I'm not sure about either of these companies.
Biotech..
  1. Biotech….Paul extremely bullish stating this could eleminate cancer, diabetes and other diseases in this decade. A French biopharmaceutical company with 8 cancer-killing drugs in its pipeline. Is able to take T-cells (white blood cells) and transform them into cancer killers. In a study, 30 patients with lymphoblastic leukemia were given this treatment. Within weeks, 27 of them were in remission. This company partnered with Pfizer. Worth under $1 billion and generates less than $50 billion in revenue. If one of the eight drugs in it’s pipeline reaches the commercialization phase, it will receive up to $2.8 billion from it’s partners. I believe this is Cellectis (CLLS).
  2. A leader in the use of psychoactive drugs for medical purposes. Wants to design drugs for international use. Recently brought in Canada’s top depression expert as CEO. One of it’s directors is a former law enforcement officer with 35 years experience in drug trafficking. I believe this is Champignon (SHRMF).
SPAC (Special-Purpose Acquisition Company)
  1. Innovation on how companies go public. Monopolizing one of the fastest-growing entertainment markets in the world. Currently holds 60% market share. (Could soar 30k+ percent). Not sure, perhaps PSTH?
  2. Another SPAC. A "pure play on American Infrastructure" with 90% recurring business. Again, not much information so I'm not sure on these ones.
Please let me know if you are able to find anything out and if you have opinions on any of the stocks, feel free to share em!
Tldr: I got clues on 10 stocks from an expensive subscription service I can’t afford. Any help identifying the stocks 1-10 above is much appreciated!
submitted by domyorke to investing [link] [comments]

Taproot, CoinJoins, and Cross-Input Signature Aggregation

It is a very common misconception that the upcoming Taproot upgrade helps CoinJoin.
TLDR: The upcoming Taproot upgrade does not help equal-valued CoinJoin at all, though it potentially increases the privacy of other protocols, such as the Lightning Network, and escrow contract schemes.
If you want to learn more, read on!

Equal-valued CoinJoins

Let's start with equal-valued CoinJoins, the type JoinMarket and Wasabi use. What happens is that some number of participants agree on some common value all of them use. With JoinMarket the taker defines this value and pays the makers to agree to it, with Wasabi the server defines a value approximately 0.1 BTC.
Then, each participant provides inputs that they unilaterally control, totaling equal or greater than the common value. Typically since each input is unilaterally controlled, each input just requires a singlesig. Each participant also provides up to two addresses they control: one of these will be paid with the common value, while the other will be used for any extra value in the inputs they provided (i.e. the change output).
The participants then make a single transaction that spends all the provided inputs and pays out to the appropriate outputs. The inputs and outputs are shuffled in some secure manner. Then the unsigned transaction is distributed back to all participants.
Finally, each participant checks that the transaction spends the inputs it provided (and more importantly does not spend any other coins it might own that it did not provide for this CoinJoin!) and that the transaction pays out to the appropriate address(es) it controls. Once they have validated the transaction, they ratify it by signing for each of the inputs it provided.
Once every participant has provided signatures for all inputs it registered, the transaction is now completely signed and the CoinJoin transaction is now validly confirmable.
CoinJoin is a very simple and direct privacy boost, it requires no SCRIPTs, needs only singlesig, etc.

Privacy

Let's say we have two participants who have agreed on a common amount of 0.1 BTC. One provides a 0.105 coin as input, the other provides a 0.114 coin as input. This results in a CoinJoin with a 0.105 coin and a 0.114 coin as input, and outputs with 0.1, 0.005, 0.014, and 0.1 BTC.
Now obviously the 0.005 output came from the 0.105 input, and the 0.014 output came from the 0.114 input.
But the two 0.1 BTC outputs cannot be correlated with either input! There is no correlating information, since either output could have come from either input. That is how common CoinJoin implementations like Wasabi and JoinMarket gain privacy.

Banning CoinJoins

Unfortunately, large-scale CoinJoins like that made by Wasabi and JoinMarket are very obvious.
All you have to do is look for a transactions where, say, more than 3 outputs are the same equal value, and the number of inputs is equal or larger than the number of equal-valued outputs. Thus, it is trivial to identify equal-valued CoinJoins made by Wasabi and JoinMarket. You can even trivially differentiate them: Wasabi equal-valued CoinJoins are going to have a hundred or more inputs, with outputs that are in units of approximately 0.1 BTC, while JoinMarket CoinJoins have equal-valued outputs of less than a dozen (between 4 to 6 usually) and with the common value varying wildly from as low as 0.001 BTC to as high as a dozen BTC or more.
This has led to a number of anti-privacy exchanges to refuse to credit custodially-held accounts if the incoming deposit is within a few hops of an equal-valued CoinJoin, usually citing concerns about regulations. Crucially, the exchange continues to hold private keys for those "banned" deposits, and can still spend them, thus this is effectively a theft. If your exchange does this to you, you should report that exchange as stealing money from its customers. Not your keys not your coins.
Thus, CoinJoins represent a privacy tradeoff:

Taproot

Let's now briefly discuss that nice new shiny thing called Taproot.
Taproot includes two components:
This has some nice properties:

Taproot DOES NOT HELP CoinJoin

So let's review!
CoinJoin:
Taproot:
There is absolutely no overlap. Taproot helps things that CoinJoin does not use. CoinJoin uses things that Taproot does not improve.

B-but They Said!!

A lot of early reporting on Taproot claimed that Taproot benefits CoinJoin.
What they are confusing is that earlier drafts of Taproot included a feature called cross-input signature aggregation.
In current Bitcoin, every input, to be spent, has to be signed individually. With cross-input signature aggregation, all inputs that support this feature are signed with a single signature that covers all those inputs. So for example if you would spend two inputs, current Bitcoin requires a signature for each input, but with cross-input signature aggregation you can sign both of them with a single signature. This works even if the inputs have different public keys: two inputs with cross-input signature aggregation effectively define a 2-of-2 public key, and you can only sign for that input if you know the private keys for both inputs, or if you are cooperatively signing with somebody who knows the private key of the other input.
This helps CoinJoin costs. Since CoinJoins will have lots of inputs (each participant will provide at least one, and probably will provide more, and larger participant sets are better for more privacy in CoinJoin), if all of them enabled cross-input signature aggregation, such large CoinJoins can have only a single signature.
This complicates the signing process for CoinJoins (the signers now have to sign cooperatively) but it can be well worth it for the reduced signature size and onchain cost.
But note that the while cross-input signature aggregation improves the cost of CoinJoins, it does not improve the privacy! Equal-valued CoinJoins are still obvious and still readily bannable by privacy-hating exchanges. It does not improve the privacy of CoinJoin. Instead, see https://old.reddit.com/Bitcoin/comments/gqb3udesign_for_a_coinswap_implementation_fo

Why isn't cross-input signature aggregation in?

There's some fairly complex technical reasons why cross-input signature aggregation isn't in right now in the current Taproot proposal.
The primary reason was to reduce the technical complexity of Taproot, in the hope that it would be easier to convince users to activate (while support for Taproot is quite high, developers have become wary of being hopeful that new proposals will ever activate, given the previous difficulties with SegWit).
The main technical complexity here is that it interacts with future ways to extend Bitcoin.
The rest of this writeup assumes you already know about how Bitcoin SCRIPT works. If you don't understand how Bitcoin SCRIPT works at the low-level, then the TLDR is that cross-input signature aggregation complicates how to extend Bitcoin in the future, so it was deferred to let the develoeprs think more about it.
(this is how I understand it; perhaps pwuille or ajtowns can give a better summary.)
In detail, Taproot also introduces OP_SUCCESS opcodes. If you know about the OP_NOP opcodes already defined in current Bitcoin, well, OP_SUCCESS is basically "OP_NOP done right".
Now, OP_NOP is a do-nothing operation. It can be replaced in future versions of Bitcoin by having that operation check some condition, and then fail if the condition is not satisfied. For example, both OP_CHECKLOCKTIMEVERIFY and OP_CHECKSEQUENCEVERIFY were previously OP_NOP opcodes. Older nodes will see an OP_CHECKLOCKTIMEVERIFY and think it does nothing, but newer nodes will check if the nLockTime field has a correct specified value, and fail if the condition is not satisfied. Since most of the nodes on the network are using much newer versions of the node software, older nodes are protected from miners who try to misspend any OP_CHECKLOCKTIMEVERIFY/OP_CHECKSEQUENCEVERIFY, and those older nodes will still remain capable of synching with the rest of the network: a dedication to strict backward-compatibility necessary for a consensus system.
Softforks basically mean that a script that passes in the latest version must also be passing in all older versions. A script cannot be passing in newer versions but failing in older versions, because that would kick older nodes off the network (i.e. it would be a hardfork).
But OP_NOP is a very restricted way of adding opcodes. Opcodes that replace OP_NOP can only do one thing: check if some condition is true. They can't push new data on the stack, they can't pop items off the stack. For example, suppose instead of OP_CHECKLOCKTIMEVERIFY, we had added a OP_GETBLOCKHEIGHT opcode. This opcode would push the height of the blockchain on the stack. If this command replaced an older OP_NOP opcode, then a script like OP_GETBLOCKHEIGHT 650000 OP_EQUAL might pass in some future Bitcoin version, but older versions would see OP_NOP 650000 OP_EQUAL, which would fail because OP_EQUAL expects two items on the stack. So older versions will fail a SCRIPT that newer versions will pass, which is a hardfork and thus a backwards incompatibility.
OP_SUCCESS is different. Instead, old nodes, when parsing the SCRIPT, will see OP_SUCCESS, and, without executing the body, will consider the SCRIPT as passing. So, the OP_GETBLOCKHEIGHT 650000 OP_EQUAL example will now work: a future version of Bitcoin might pass it, and existing nodes that don't understand OP_GETBLOCKHEIGHT will se OP_SUCCESS 650000 OP_EQUAL, and will not execute the SCRIPT at all, instead passing it immediately. So a SCRIPT that might pass in newer versions will pass for older versions, which keeps the back-compatibility consensus that a softfork needs.
So how does OP_SUCCESS make things difficult for cross-input signatur aggregation? Well, one of the ways to ask for a signature to be verified is via the opcodes OP_CHECKSIGVERIFY. With cross-input signature aggregation, if a public key indicates it can be used for cross-input signature aggregation, instead of OP_CHECKSIGVERIFY actually requiring the signature on the stack, the stack will contain a dummy 0 value for the signature, and the public key is instead added to a "sum" public key (i.e. an n-of-n that is dynamically extended by one more pubkey for each OP_CHECKSIGVERIFY operation that executes) for the single signature that is verified later by the cross-input signature aggregation validation algorithm00.
The important part here is that the OP_CHECKSIGVERIFY has to execute, in order to add its public key to the set of public keys to be checked in the single signature.
But remember that an OP_SUCCESS prevents execution! As soon as the SCRIPT is parsed, if any opcode is OP_SUCCESS, that is considered as passing, without actually executing the SCRIPT, because the OP_SUCCESS could mean something completely different in newer versions and current versions should assume nothing about what it means. If the SCRIPT contains some OP_CHECKSIGVERIFY command in addition to an OP_SUCCESS, that command is not executed by current versions, and thus they cannot add any public keys given by OP_CHECKSIGVERIFY. Future versions also have to accept that: if they parsed an OP_SUCCESS command that has a new meaning in the future, and then execute an OP_CHECKSIGVERIFY in that SCRIPT, they cannot add the public key into the same "sum" public key that older nodes use, because older nodes cannot see them. This means that you might need more than one signature in the future, in the presence of an opcode that replaces some OP_SUCCESS.
Thus, because of the complexity of making cross-input signature aggregation work compatibly with future extensions to the protocol, cross-input signature aggregation was deferred.
submitted by almkglor to Bitcoin [link] [comments]

Technical: Taproot: Why Activate?

This is a follow-up on https://old.reddit.com/Bitcoin/comments/hqzp14/technical_the_path_to_taproot_activation/
Taproot! Everybody wants it!! But... you might ask yourself: sure, everybody else wants it, but why would I, sovereign Bitcoin HODLer, want it? Surely I can be better than everybody else because I swapped XXX fiat for Bitcoin unlike all those nocoiners?
And it is important for you to know the reasons why you, o sovereign Bitcoiner, would want Taproot activated. After all, your nodes (or the nodes your wallets use, which if you are SPV, you hopefully can pester to your wallet vendoimplementor about) need to be upgraded in order for Taproot activation to actually succeed instead of becoming a hot sticky mess.
First, let's consider some principles of Bitcoin.
I'm sure most of us here would agree that the above are very important principles of Bitcoin and that these are principles we would not be willing to remove. If anything, we would want those principles strengthened (especially the last one, financial privacy, which current Bitcoin is only sporadically strong with: you can get privacy, it just requires effort to do so).
So, how does Taproot affect those principles?

Taproot and Your /Coins

Most HODLers probably HODL their coins in singlesig addresses. Sadly, switching to Taproot would do very little for you (it gives a mild discount at spend time, at the cost of a mild increase in fee at receive time (paid by whoever sends to you, so if it's a self-send from a P2PKH or bech32 address, you pay for this); mostly a wash).
(technical details: a Taproot output is 1 version byte + 32 byte public key, while a P2WPKH (bech32 singlesig) output is 1 version byte + 20 byte public key hash, so the Taproot output spends 12 bytes more; spending from a P2WPKH requires revealing a 32-byte public key later, which is not needed with Taproot, and Taproot signatures are about 9 bytes smaller than P2WPKH signatures, but the 32 bytes plus 9 bytes is divided by 4 because of the witness discount, so it saves about 11 bytes; mostly a wash, it increases blockweight by about 1 virtual byte, 4 weight for each Taproot-output-input, compared to P2WPKH-output-input).
However, as your HODLings grow in value, you might start wondering if multisignature k-of-n setups might be better for the security of your savings. And it is in multisignature that Taproot starts to give benefits!
Taproot switches to using Schnorr signing scheme. Schnorr makes key aggregation -- constructing a single public key from multiple public keys -- almost as trivial as adding numbers together. "Almost" because it involves some fairly advanced math instead of simple boring number adding, but hey when was the last time you added up your grocery list prices by hand huh?
With current P2SH and P2WSH multisignature schemes, if you have a 2-of-3 setup, then to spend, you need to provide two different signatures from two different public keys. With Taproot, you can create, using special moon math, a single public key that represents your 2-of-3 setup. Then you just put two of your devices together, have them communicate to each other (this can be done airgapped, in theory, by sending QR codes: the software to do this is not even being built yet, but that's because Taproot hasn't activated yet!), and they will make a single signature to authorize any spend from your 2-of-3 address. That's 73 witness bytes -- 18.25 virtual bytes -- of signatures you save!
And if you decide that your current setup with 1-of-1 P2PKH / P2WPKH addresses is just fine as-is: well, that's the whole point of a softfork: backwards-compatibility; you can receive from Taproot users just fine, and once your wallet is updated for Taproot-sending support, you can send to Taproot users just fine as well!
(P2WPKH and P2WSH -- SegWit v0 -- addresses start with bc1q; Taproot -- SegWit v1 --- addresses start with bc1p, in case you wanted to know the difference; in bech32 q is 0, p is 1)
Now how about HODLers who keep all, or some, of their coins on custodial services? Well, any custodial service worth its salt would be doing at least 2-of-3, or probably something even bigger, like 11-of-15. So your custodial service, if it switched to using Taproot internally, could save a lot more (imagine an 11-of-15 getting reduced from 11 signatures to just 1!), which --- we can only hope! --- should translate to lower fees and better customer service from your custodial service!
So I think we can say, very accurately, that the Bitcoin principle --- that YOU are in control of your money --- can only be helped by Taproot (if you are doing multisignature), and, because P2PKH and P2WPKH remain validly-usable addresses in a Taproot future, will not be harmed by Taproot. Its benefit to this principle might be small (it mostly only benefits multisignature users) but since it has no drawbacks with this (i.e. singlesig users can continue to use P2WPKH and P2PKH still) this is still a nice, tidy win!
(even singlesig users get a minor benefit, in that multisig users will now reduce their blockchain space footprint, so that fees can be kept low for everybody; so for example even if you have your single set of private keys engraved on titanium plates sealed in an airtight box stored in a safe buried in a desert protected by angry nomads riding giant sandworms because you're the frickin' Kwisatz Haderach, you still gain some benefit from Taproot)
And here's the important part: if P2PKH/P2WPKH is working perfectly fine with you and you decide to never use Taproot yourself, Taproot will not affect you detrimentally. First do no harm!

Taproot and Your Contracts

No one is an island, no one lives alone. Give and you shall receive. You know: by trading with other people, you can gain expertise in some obscure little necessity of the world (and greatly increase your productivity in that little field), and then trade the products of your expertise for necessities other people have created, all of you thereby gaining gains from trade.
So, contracts, which are basically enforceable agreements that facilitate trading with people who you do not personally know and therefore might not trust.
Let's start with a simple example. You want to buy some gewgaws from somebody. But you don't know them personally. The seller wants the money, you want their gewgaws, but because of the lack of trust (you don't know them!! what if they're scammers??) neither of you can benefit from gains from trade.
However, suppose both of you know of some entity that both of you trust. That entity can act as a trusted escrow. The entity provides you security: this enables the trade, allowing both of you to get gains from trade.
In Bitcoin-land, this can be implemented as a 2-of-3 multisignature. The three signatories in the multisgnature would be you, the gewgaw seller, and the escrow. You put the payment for the gewgaws into this 2-of-3 multisignature address.
Now, suppose it turns out neither of you are scammers (whaaaat!). You receive the gewgaws just fine and you're willing to pay up for them. Then you and the gewgaw seller just sign a transaction --- you and the gewgaw seller are 2, sufficient to trigger the 2-of-3 --- that spends from the 2-of-3 address to a singlesig the gewgaw seller wants (or whatever address the gewgaw seller wants).
But suppose some problem arises. The seller gave you gawgews instead of gewgaws. Or you decided to keep the gewgaws but not sign the transaction to release the funds to the seller. In either case, the escrow is notified, and if it can sign with you to refund the funds back to you (if the seller was a scammer) or it can sign with the seller to forward the funds to the seller (if you were a scammer).
Taproot helps with this: like mentioned above, it allows multisignature setups to produce only one signature, reducing blockchain space usage, and thus making contracts --- which require multiple people, by definition, you don't make contracts with yourself --- is made cheaper (which we hope enables more of these setups to happen for more gains from trade for everyone, also, moon and lambos).
(technology-wise, it's easier to make an n-of-n than a k-of-n, making a k-of-n would require a complex setup involving a long ritual with many communication rounds between the n participants, but an n-of-n can be done trivially with some moon math. You can, however, make what is effectively a 2-of-3 by using a three-branch SCRIPT: either 2-of-2 of you and seller, OR 2-of-2 of you and escrow, OR 2-of-2 of escrow and seller. Fortunately, Taproot adds a facility to embed a SCRIPT inside a public key, so you can have a 2-of-2 Taprooted address (between you and seller) with a SCRIPT branch that can instead be spent with 2-of-2 (you + escrow) OR 2-of-2 (seller + escrow), which implements the three-branched SCRIPT above. If neither of you are scammers (hopefully the common case) then you both sign using your keys and never have to contact the escrow, since you are just using the escrow public key without coordinating with them (because n-of-n is trivial but k-of-n requires setup with communication rounds), so in the "best case" where both of you are honest traders, you also get a privacy boost, in that the escrow never learns you have been trading on gewgaws, I mean ewww, gawgews are much better than gewgaws and therefore I now judge you for being a gewgaw enthusiast, you filthy gewgawer).

Taproot and Your Contracts, Part 2: Cryptographic Boogaloo

Now suppose you want to buy some data instead of things. For example, maybe you have some closed-source software in trial mode installed, and want to pay the developer for the full version. You want to pay for an activation code.
This can be done, today, by using an HTLC. The developer tells you the hash of the activation code. You pay to an HTLC, paying out to the developer if it reveals the preimage (the activation code), or refunding the money back to you after a pre-agreed timeout. If the developer claims the funds, it has to reveal the preimage, which is the activation code, and you can now activate your software. If the developer does not claim the funds by the timeout, you get refunded.
And you can do that, with HTLCs, today.
Of course, HTLCs do have problems:
Fortunately, with Schnorr (which is enabled by Taproot), we can now use the Scriptless Script constuction by Andrew Poelstra. This Scriptless Script allows a new construction, the PTLC or Pointlocked Timelocked Contract. Instead of hashes and preimages, just replace "hash" with "point" and "preimage" with "scalar".
Or as you might know them: "point" is really "public key" and "scalar" is really a "private key". What a PTLC does is that, given a particular public key, the pointlocked branch can be spent only if the spender reveals the private key of the given public key to you.
Another nice thing with PTLCs is that they are deniable. What appears onchain is just a single 2-of-2 signature between you and the developemanufacturer. It's like a magic trick. This signature has no special watermarks, it's a perfectly normal signature (the pledge). However, from this signature, plus some datta given to you by the developemanufacturer (known as the adaptor signature) you can derive the private key of a particular public key you both agree on (the turn). Anyone scraping the blockchain will just see signatures that look just like every other signature, and as long as nobody manages to hack you and get a copy of the adaptor signature or the private key, they cannot get the private key behind the public key (point) that the pointlocked branch needs (the prestige).
(Just to be clear, the public key you are getting the private key from, is distinct from the public key that the developemanufacturer will use for its funds. The activation key is different from the developer's onchain Bitcoin key, and it is the activation key whose private key you will be learning, not the developer's/manufacturer's onchain Bitcoin key).
So:
Taproot lets PTLCs exist onchain because they enable Schnorr, which is a requirement of PTLCs / Scriptless Script.
(technology-wise, take note that Scriptless Script works only for the "pointlocked" branch of the contract; you need normal Script, or a pre-signed nLockTimed transaction, for the "timelocked" branch. Since Taproot can embed a script, you can have the Taproot pubkey be a 2-of-2 to implement the Scriptless Script "pointlocked" branch, then have a hidden script that lets you recover the funds with an OP_CHECKLOCKTIMEVERIFY after the timeout if the seller does not claim the funds.)

Quantum Quibbles!

Now if you were really paying attention, you might have noticed this parenthetical:
(technical details: a Taproot output is 1 version byte + 32 byte public key, while a P2WPKH (bech32 singlesig) output is 1 version byte + 20 byte public key hash...)
So wait, Taproot uses raw 32-byte public keys, and not public key hashes? Isn't that more quantum-vulnerable??
Well, in theory yes. In practice, they probably are not.
It's not that hashes can be broken by quantum computes --- they're still not. Instead, you have to look at how you spend from a P2WPKH/P2PKH pay-to-public-key-hash.
When you spend from a P2PKH / P2WPKH, you have to reveal the public key. Then Bitcoin hashes it and checks if this matches with the public-key-hash, and only then actually validates the signature for that public key.
So an unconfirmed transaction, floating in the mempools of nodes globally, will show, in plain sight for everyone to see, your public key.
(public keys should be public, that's why they're called public keys, LOL)
And if quantum computers are fast enough to be of concern, then they are probably fast enough that, in the several minutes to several hours from broadcast to confirmation, they have already cracked the public key that is openly broadcast with your transaction. The owner of the quantum computer can now replace your unconfirmed transaction with one that pays the funds to itself. Even if you did not opt-in RBF, miners are still incentivized to support RBF on RBF-disabled transactions.
So the extra hash is not as significant a protection against quantum computers as you might think. Instead, the extra hash-and-compare needed is just extra validation effort.
Further, if you have ever, in the past, spent from the address, then there exists already a transaction indelibly stored on the blockchain, openly displaying the public key from which quantum computers can derive the private key. So those are still vulnerable to quantum computers.
For the most part, the cryptographers behind Taproot (and Bitcoin Core) are of the opinion that quantum computers capable of cracking Bitcoin pubkeys are unlikely to appear within a decade or two.
So:
For now, the homomorphic and linear properties of elliptic curve cryptography provide a lot of benefits --- particularly the linearity property is what enables Scriptless Script and simple multisignature (i.e. multisignatures that are just 1 signature onchain). So it might be a good idea to take advantage of them now while we are still fairly safe against quantum computers. It seems likely that quantum-safe signature schemes are nonlinear (thus losing these advantages).

Summary

I Wanna Be The Taprooter!

So, do you want to help activate Taproot? Here's what you, mister sovereign Bitcoin HODLer, can do!

But I Hate Taproot!!

That's fine!

Discussions About Taproot Activation

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In this type of chart the value of the variable changes its meaning to a new meaning: the number of times the variable is over its average geometric growth. In the case of the fair value chart, we are detrending the depicted variables with respect to the price average geometric growth (and not with respect to the fair value). A Bitcoin transaction is a contract that transfers bitcoins, between wallets. The wallets are interfaces for keys, and the corresponding addresses those keys have dominion over. Bitcoin Dust. The Bitcoin Core reference implementation defines dust as an output where the fee to required to move it is greater than 1/3 its value. Put more simply, dust is low-value bitcoins wherein the transaction fee incurred in moving them is greater than the value of the bitcoins themselves. Verification. To verify that inputs are authorized to collect the values of referenced outputs, Bitcoin uses a custom Forth-like scripting system. The input's scriptSig and the referenced output's scriptPubKey are evaluated (in that order), with scriptPubKey using the values left on the stack by scriptSig. The input is authorized if scriptPubKey returns true. Estimated Transaction Value (BTC) The total estimated value in BTC of transactions on the blockchain. This does not include coins returned as change. This does not include coins returned as change. 30 Days 60 Days 180 Days 1 Year 3 Years All Time

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260 TIP. Bitcoin Math & Value with Plan B - YouTube

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