Bitcoin has returned to the front pages of major media thanks to a spectacular jump in its value (18.3 percent for the last seven days). That doesn't mean you can or should mine bitcoins at home, but if that task only interests you as an experiment, then you need to know that many devices have the ability to compute hashes, including the Apollo Guidance Computer (AGC). At an average of 40,000 operations per second, the AGC is going to take a little while...
Bitcoin crossed the $12,000 barrier again. Not a few players have advanced the purchase of graphics cards or raised the prices of their used models, speculating about a possible new arms race between alternative cryptocurrencies. However, Bitcoin is a universe in itself, and it doesn't stay still for too long. At the time of writing these lines, the trend is downward, and the rest of the platforms are basically following it.
Now let's set aside the economic-financial aspect of Bitcoin. What brings us together today is its mathematical profile, and the work of Ken Shirriff, a fairly well-known name here. After all, he taught us how basic circuits work, the creation of Christmas cards with an IBM 1401, and the mining of bitcoins using pencil and paper. What did he use this time? Nothing less than the famous AGC, the Apollo Guidance Computer.
In relaxed terms, to mine a block on the Bitcoin platform you need to calculate a very special hash. The reward is enormous (12.5 bitcoins or 150 thousand dollars every 10 minutes on average), and so is the difficulty. That hash must start with 18 zeros, a condition that forces miners (who also compete among themselves) to generate billions and billions of hashes until they find the right one. The solution for miners is pure brute force: Farms with thousands of devices that devour energy and become obsolete in record time.
However, with only 4 kilobytes of memory and 40,000 operations per second (a monstrosity for the time), the Apollo Guidance Computer can do little against the complexity of Bitcoin. To save (a lot of) time, Shirriff decided to process an already mined block. The AGC took 5.15 seconds to find a hash, but Bitcoin uses the double-hash, so we are looking at one Bitcoin hash every 10.3 seconds. How long would the Apollo Guidance Computer take to find a block? With the current difficulty, 4x10^23 seconds. If we consider that the age of the Universe is 4.3x10^17 seconds, we would need to wait for the AGC a million times that number.
That's not all we have to share about the Apollo mission. Its source code is still available, as well as a letter from Richard Nixon that luckily he never had to read.
Official site: Click here.
