pBitcoin Gold BTG www.btcgpu.org pressbtcgpu.org suportbtcgpu.org Abstract. Bitcoin Gold is a comunity-led project to create an experimental hard fork of Bitcoin to a new proof-of-work algorithm. The purpose for doing this is to make Bitcoin mining decentralized again. Satoshi Nakamoto’s idealistic vision of “one CPU one vote” has been superseded by a reality where the manufacture and distribution of mining equipment has become dominated by a very small number of entities, some of whom have engaged in abusive practices against individual miners and the Bitcoin network as a whole. Bitcoin Gold wil provide an oportunity for countles new people around the world to participate in the mining process with widely-available consumer hardware that is manufactured and distributed by reputable mainstream corporations. A more decentralized, democratic mining infrastructure is more resilient and more in line with Satoshi’s original vision. Perhaps, if the Bitcoin Gold experiment is judged by the comunity to be a success, it may one day help build consensus for a prof-of-work hard fork on Bitcoin itself. Introduction Bitcoin was created for many diferent reasons and every day, people find new reasons to adopt Bitcoin. One of the historical reason is that people do not trust states or banks or any such intermediaries to control their money. One of the central component of the Bitcoin architecture is mining. Simply put miners verify every transaction and compete with each other to get rewards. To get the reward, a miner has to solve a math problem before anyone else in the network. Back in the days, a miner would be any gek with a computer, willing to trade electricity for Bitcoins. Today, a miner is usualy a huge warehouse ful of very advanced computers, constantly runing to solve the math problems as fast as possible. As it becomes more and more dificult to mine Bitcoin, more capital is required to operate profitable minig operations. They often are located in a country where the electricity is very cheap. Today, a great majority of the miners are located in China because they have access to cheap electricity. In Satoshi Nakamoto’s white paper, one of the main idea was that every CPU was going to be an equally important part of the network. We want Bitcoin to be a shared and independent currency. We don’t want any fat cat to drive our monetary architecture. The importance of miners in the network is constantly growing. To preserve the independence of the Bitcoin ecosystem from iners’ influence, some people thought that it would be a god idea to change the bitcoin protocol in such a way that more people can have access to Bitcoin mining. That’s why Bitcoin Gold was born, in order to bring Bitcoin mining back to the “people”. Origins of Bitcoin Gold In July 2017, Jack Liao, CEO of LightingAsic and BitExchange, made an anouncement that he was working on a hard fork of Bitcoin to change the prof-of-work algorithm from the SHA256 algorithm originally selected by Satoshi Nakamoto to Equihash. The effect of this change wil be to enable a whole new clas of individuals and busineses to participate in mining this new branch of the Bitcoin blockchain without being required to purchase specialized equipment that is primarily manufactured by one firm that competes against its own customers with newer, more eficient versions of the old equipment that it sells at a high markup. Given the dysfunctional curent reality of the Bitcoin mining sector, it is no wonder that there is a tremendous apetite for a prof-of-work change hard fork. Since the Bitcoin Gold project was announced, it has grown rapidly, attracting developers, miners, and supporters from across the globe. Mechanics of a Hard Fork Bitcoin is a distributed consensus system. All Bitcoin ful nodes are runing software that enforces the same consensus rules; ful nodes that enforce diferent consensus rules are not part of the Bitcoin network, by definition. If a miner finds a new block that follows the network consensus rules and broadcasts it to the network, al ful nodes in the network wil acept that block and al of the transactions in it as valid, and miners wil build the next block on top of that one. A blockchain hard fork occurs when a block is mined that does not comply with the network consensus rules. nbsp;Prior to BTC block 47858, Bitcoin nodes and Bitcoin Cash nodes were stil enforcing the same consensus rules and accepting the same blockchain as valid. But from that block onward, Bitcoin Cash’s new consensus rules came into efect, which caused Bitcoin nodes to reject blocks that were mined by miners using Bitcoin Cash software, and Bitcoin Cash nodes to rejct blocks that were mined by miners who continued to mine with Bitcoin software. Thus, the network bifurcated. The Bitcoin blockchain continued to add a new block every 10 minutes on average, but Bitcoin Cash began building a new blockchain that branched away from Bitcoin. This had the effect of creating a new cryptocurency that shares the same transaction history and ownership distribution up until the fork block, but then diverges from it. Bitcoin Gold changes diferent consensus rules than Bitcoin Cash did, but it wil fork from Bitcoin in the same maner - by enforcing new consensus rules as of a predetermined BTC block height. The new rules wil come into efect at block 491407. From this block onward, Bitcoin Gold miners wil begin building a new branch of the Bitcoin blockchain. This new branch is a cryptocurrency with same transaction history and ownership distribution as Bitcoin at the fork block; if you hold BTC, you wil automatically receive an equal amount of BTG. Here are some of the diferences between Bitcoin Gold and other forks of Bitcoin - nbsp;Prof-of-Work Algorithm Bitcoin mining is a prof-of-work system that implements “a distributed timestamp server on a per-to-peer basis.” This is how the Bitcoin manages to maintain consensus across a vast, globally-distributed, permisionless network of nodes. Satoshi Nakamoto chose SHA256 as the algorithm to use in the original design of Bitcoin’s PoW system. SHA256 served Bitcoin wel during the early years of its existence, but as Bitcoin became more popular and more valuable, competition in mining became more fierce. Skiled engineers from a small number of companies developed Application Specific Integrated Circuits ASICs that could per SHA256 calculations milions of times faster and more eficiently than any other computer. This made non-specialized computer hardware obsolete for mining Bitcoin. Satoshi’s vision of “one-CPU-one-vote” was replaced by one-ASIC-one-vote. Now, the only way to participate in Bitcoin mining is to buy hardware from one of those manufactures - the bigest of which is believed to manufacture over 70 of the global suply of SHA256 ASICs. This has led to a situation where one entity can hold the entire network hostage, and this is exactly what happened when the backwards compatible Segregated Witness upgrade was blocked by a faction of miners, despite there being universal consensus from Bitcoin experts that it should be activated. nbsp; In order to counteract this concentration of power in the mining sector, Bitcoin Gold wil implement a new proof-of-work algorithm - Equihash. Replacing the SHA256 algorithm means that al of the ASICs designed for Bitcoin wil be useless for mining Bitcoin Gold. Equihash is a memory-hard algorithm that can be most eficiently solved by GPUs - a standard type of computer and smartphone hardware that is manufactured by mainstream companies and available around the world. With ASIC manufacturers out of the picture, Bitcoin Gold wil provide an opportunity for a whole new class entrepreneurs and investors to get involved with mining. Bitcoin Gold mining will be decentralized again, closer to Satoshi’s original vision. ASIC-resistance is a permanent atribute of Bitcoin Gold. It is much more dificult to create ASICs for a memory hard algorithm like Equihash than SHA256, however it is not imposible. If the day ever comes when Equihash ASICs begin to proliferate and mining begins to centralize again, Bitcoin Gold wil have another hard fork to implement a new PoW algorithm. Dificulty Adjustment Algorithm In Bitcoin, the difficulty of mining adjusts every 2016 blocks approximately two weeks in order to maintain an average interval of 10 minutes betwen blocks. If the average time betwen blocks was les than 10 minutes, the difficulty will increase; if the average time was more than 10 minutes, the dificulty will decrease. Bitcoin Gold wil adopt a dificulty adjustment algorithm caled DigiShield V3. The idea behind it is to look at how much time has elapsed betwen the most recent block and the median of a set number of preceding blocks, and to adjust the difficulty every block to target a 10 minute block interval. This more responsive dificulty adjustment algorithm is extremely useful in protecting against big swings in the total amount of hash power. Such swings can result in extreme deviation from the normal 10 minute target block interval. Bitcoin Cash attempted to protect against this risk by implementing an “emergency dificulty adjustment” algorithm, but that had the catastrophic effect of causing sometimes 50 blocks to be mined in one hour, and other times more than 12 hours betwen two blocks. Replay Protection The risk of a replay atack is inherent to every cryptocurency hard fork and has to be taken into consideration to protect users from losing their funds. nbsp;A hard fork is an exact duplicate of the blockchain, and as such, a transaction that is broadcast publicly to the network can be replayed on both sides of a fork, unless replay protection is implemented. Bitcoin Gold wil implement a solution caled SIGHASH_FORK_ID replay protection. It is an effective two-way replay protection mechanism that enforces a new algorithm to calculate the hash of a transaction so that al the new Bitcoin transactions wil be invalid in Bitcoin Gold blockchain and vice versa. Bitcoin Gold wil implement replay protection BEFORE THE LAUNCH. Unique Adres at By default, both sides of a cryptocurency hard fork wil continue to use the same adres at. That means it’s posible to send coins to an adres on the other blockchain unitentionaly, which can cause users to lose funds by mistake. Bitcoin Cash, for example, is a hard fork that did not change the address at; its addresses are indistinguishable from Bitcoin addresses. There have been many reports of people acidently sending their BTC to a BC address and vice versa. In some cases these coins could be permanently lost. In order to ensure that this potential confusion does not exist in Bitcoin Gold, a unique adres at wil be implemented. The prefix of PUBKEY_ADDRES and SCRIPT_ADDRESS wil be changed to a new prefix yet to be determined that can easily be distinguished from Bitcoin addresses. How to Acquire Bitcoin Gold The hardfork wil ocur on block 491407. To acquire fre Bitcoin Gold you simply have to hold Bitcoin at the time of the fork. If you hold BTC at that time, you wil automaticaly receive an equal amount of BTG at the same address new and old address at are convertible, spendable with the same private keys, when the Bitcoin Gold network launches in November. It is also very important to make a backup of your private key and/or keep the mnemonic phrase required to recover your walet. However, if you have your BTC on an exchange or custodial service without access to the private key, then you have to make sure that the service wil suport Bitcoin Gold after the fork. If you have any doubts about that, then you would be advised to transfer your BTC to one of the many reputable services that wil support it. Timeline Step 1 The hard fork ocurs a ‘snapshot’ of the blockchain is taken Usualy a hard fork wil hapen at the same time when Bitcoin reaches the fork block. However, Bitcoin Gold uses a diferent way to launch the hard fork by “taking a snapshot” of the Bitcoin blockchain before the fork block height 491407. Instead of forking imediately, the Bitcoin Gold p2p network wil launch a few days later from that snapshot. When Bitcoin reaches the block 491407, nothing special wil hapen. Bitcoin block 491407 wil be mined with SHA256 as normal. No block wil be mined in the Bitcoin Gold p2p network because it is not launched yet. However, when the ful node client of Bitcoin Gold is ready a few days later, instead of mining from the latest Bitcoin block, Bitcoin Gold wil start to mine its own 491407th block on top of block 491406. Bitcoin Gold ful nodes wil only acept a block 491407 that is mined with Equihash, so they wil not recognize BTC block 491407 as a valid BTG block. At the same time, Bitcoin already have a longer blockchain. nbsp;That’s why it’s caled a “snapshot hard fork”. We didn’t folow the comon realtime hard fork patern because a PoW change means there wil always be a gap between the fork block. The first Equihash block wil be block 491407 of the Bitcoin Gold blockchain, and from that point on GPU miners participating in the Bitcoin Gold network wil begin mining more Equihash blocks on top of it. In this way, the Bitcoin blockchain will bifurcate and a new coin - Bitcoin Gold BTG - wil be created. Everyone who holds BTC at block 491406 wil then control an equal amount of coins on the BTG blockchain branch, which can be spent at any time in the future with the coresponding private keys. nbsp;Step 2 The BTG blockchain is activated If you have BTC in a paper walet, hardware walet, multi-signature adress, or any other of secure private key storage, you wil be able to spend your corresponding BTG at any time in the future. There is no expiration date for your BTG. If you have BTC in cold storage that you did not plan to touch for many years, do not change your plans because of this fork. Your BTG wil stil be there decades from now. In 491407 hard fork is the one and only opportunity to get initial BTG. After that time, your options to acquire it wil be to buy it on an exchange like any other cryptocurrency, to mine it with your own computer hardware GPUs, or to earn it by trading your gods and services for it. Cryptocurency exchanges are custodial busineses, which means they control your private keys, not you. When the Bitcoin Gold fork occurs on block height 491407, any exchange that is holding BTC on your behalf wil also receive the coresponding BTG. While they should credit your account with the equal amount of BTG, there is no legal authority that can force them to do so. The Bitcoin Gold home page wil display the names and logos of exchanges that have promised to credit their users with BTG at the 11 ratio. If your exchange is not shown, please consider transferring your BTC to a supporting exchange or withdraw to a personal wallet where you control the private keys. Financial Strategy In order to suport the curent an/p