Very late reply, but in case anybody sees this. The "shaken mix" of fingerprint + random number must produce a number that is lower than a certain target number

Very late reply, but in case anybody sees this. The "shaken mix" of fingerprint + random number must produce a number that is lower than a certain target number. The most visible consequence of this is that the accepted numbers must begin with a string of zeros (as the number of digits is fixed, as in 0003 is lower than 0123). Example: Not a good mix: 1312af178c253f84028d480a6adc1e25e81caa44c749ec81976192e2ec934c64 A good mix: 0000000000000000057fcc708cf0130d95e27c5819203e9f967ac56e4df598ee This "shaken mix" is a SHA-256 hash of the current block plus a random number. SHA-256 is an algorithm that generates a "fingerprint" (called "hash") of a block of data, in such a way that it is not possible to determine, from the fingerprint itself, which data might have generated it [otherwise it would be possible to start from (a set of) desired fingerprints and calculate back to the set of possible blocks that could generate them].