By hand. Long ago, cryptanalysis was done by hand. People would count the frequencies of symbols, compare encrypted text to decrypted text, and try to find patterns. It was a meticulous process which required days and weeks of concentration. Starting with World War II, the heavy lifting was transferred to machines and humans experts started spending their time on problems in pure mathematics which enabled them to crack all but the toughest ciphers. But even today, cryptanalysts spend much of their time meticulously dissecting the structure of the cipher they’re trying to crack. Does this need to be the case?