IIRC the Colossus machine built during WW2 was basically counting the number of bits resulting from doing various boolean operations on the input. It was used t

IIRC the Colossus machine built during WW2 was basically counting the number of bits resulting from doing various boolean operations on the input. It was used to crack the Lorenz cipher, which XORed the plaintext with a pseudo-random keystream (generated using mechanical rotors!). Cryptography has advanced since then - and I'm not an expert - but there may still be statistical weaknesses that could be found by counting bits?