Bitcoin mining is one of the most demanding activities around these days. Not only is there a significant amount of money at stake, but the constant increase in computational complexity makes state-of-the-art hardware obsolete overnight. Still, Bitcoin mining is fundamentally a mathematical operation, and Ken Shirriff recently proved that it can be done with a pencil and paper. Slowly… but it can be done.
Unless you're willing to make a bet of several hundred thousand dollars on hardware and energy, the most logical thing these days for mining Bitcoins is to join a “pool”. But not many people have stopped to explain in simple terms the theory behind Bitcoin mining. Fortunately for all of us, Ken Shirriff does exactly that on his personal blog.
In essence, Bitcoin miners group transactions into a block, and repeat millions of times a cryptographic operation (the famous hashing) until they find a hash with a very rare value. How rare? At the difficulty level Shirriff did the exercise (about five years earlier) only one out of every 1.4 x 10^20 hashes is correct. The hash function is SHA-256, which for security is applied twice.
The SHA-256 hash algorithm takes small 512-bit blocks, performs a ciphered combination, and as a result outputs a 256-bit value. This is repeated 64 times, but despite the daunting numbers, it can be calculated by hand, and when I say “by hand” I mean writing everything down on a sheet of paper. It took Shirriff 16 minutes and 45 seconds to complete one round of SHA-256 hashing.
Working non-stop, the complete operation would take just over 17 and a half hours. Multiplied by two (let's not forget that SHA-256 is applied twice), the total effort to hash a Bitcoin block exceeds 35 hours. In terms we can relate to current mining machines, Shirriff's performance was 0.67 hashes per day.
As if that weren't enough, Shirriff decided to calculate the energy consumption during his manual mining. Assuming a metabolic rate of 1,500 calories per day, his process consumes about ten megajoules (or megajoules if you prefer) per hash. If we consider that mining hardware has an efficiency on the order of 1,000 megahashes per joule, Shirriff's efficiency loss is by a factor of 10^16.
In other words, it may be very interesting as a mathematical exercise, but Bitcoin mining is something that definitely belongs to machines. Moreover, a new block is mined every ten minutes, so a manually calculated block would be obsolete by the time it was integrated.
Want more computer exercises to do on paper? Make your own paper processor and a paper calculator to learn the binary system.
https://old.neoteo.com/por-que-no-soy-millonario-de-la-vez-que-casi-compro-100-bitcoins/
