We already know the most probable reason for the reluctance of some mines to introduce SegWit. All signs point to the AsicBoost technology used in excavators, which will become useless after the amendment. We now know the most probable reason for the reluctance of some mines to introduce SegWit. All signs point to the AsicBoost technology used in excavators, which will become useless after the amendment. As a result of the disputes over the maximum block size, a division into two factions has arisen. One supports a group of Bitcoin Core developers who see increased network capacity in the introduction of the Segregated Witness modification (called SegWit for short), followed by higher layer protocols such as Lightning Network. The other faction, associated with the largest mines, relies on a simple increase in block size, Bitcoin Unlimited. The two factions are fighting each other without disguise. Last Wednesday Gregory Maxwell, one of Core's developers, brought out another cannon, accusing the mines (actually one, more on that later) of using AsicBoost, a "dirty trick" called - perhaps exaggeratedly - an attack on a vulnerability in the Bitcoin protocol. The term was used in a post on the bitcoin-dev mailing list. What is AsicBoost? It is a way to reduce the amount of computing power required to solve a block at a given difficulty level. This results in a power savings of 20 to 30%. What's more, an excavator chip using this technique can take up less space on a silicon lobe. This increases the so-called yield (the percentage of efficient chips obtained from a single "wafer"), which means it reduces the price of the chips themselves. AsicBoost was invented and patented by German scientist Dr. Timo Hanke. It is by no means new or previously unknown. The smallest unit of computational work performed by a Bitcoin miner is to try for a particular version of a block all of the possible 4 billion combinations of a 32-bit number (called salts). Each combination means counting the SHA-256 hash function twice. However, it turned out that by using knowledge about the structure of the block header, the amount of data needed to process can be reduced. As a result, solving a block on average requires 25% less computation and that much less power. Technical gibberish} The PoW (Proof of Work) function in Bitcoin - or "hashing" - involves performing a sha256 hash first on the 80-byte block header and then on the result of that hash. The result of the hash is always a 256-bit number, so it pays to design a separate chip that performs the first hash (from the 640-bit header) and the second from less data. This allows for parallel/synchronous operation of both parts - the result of the first hash is passed to the second hash before the whole first hash is calculated. Due to the structure of the block header, the first part of the computation can be simplified by assuming that some part of the header will have a fixed value (or a specific set of values). Appropriate manipulation of the extranonce field in the generation transaction (which automatically changes the hash of the block transaction tree) allows the required part of the block header to be obtained at the cost of less computation than counting the hash disregarding the hashed data. The time spent preparing the data pays for itself in less hash time. Since AsicBoost is a hardware-level development and not a software-level development, once SegWit comes into effect, it may be that a sizable portion of excavators will not be able to be used for bitcoin mining or their demonstrated power will drop by 20-30% or the power consumption of the excavators will increase. The introduction of SegWit would therefore be a blow to both the equipment manufacturers using this solution (miners will no longer meet the declared parameters) and the miners (increase in power consumption or decrease in hashrate). If AsicBoost-enabled miners were to stop working, the computing power of the network could drop dramatically overnight. Maxwell said that based on the reverse engineering performed on one vendor's chips, it was found that they were secretly using the AsicBoost feature. It is an open secret that this manufacturer is BitMain, which is using its chips en masse in the AntPool mine. Interestingly, Dr. Hanke seemed to be unaware of this, so if this is true, then the Chinese have ignored the patent. To make things funnier, BitMain itself reportedly patented AsicBoost in China. The SegWit patch promoted by the Bitcoin Core team renders AsicBoost useless, due to the information stored in the block header. Therefore, Core's bias suggests that this is the real reason for AntPool's blocking of SegWit. Maxwell estimated the profits from AsicBoost (for a mine with about half the network capacity) at $100 million per year. The case is not so clear-cut, however. There is no conclusive proof of AntPool's use of AsicBoost. It does not j
No comments:
Post a Comment