Keccak for xkcp and NIST for the padding, as far as I can remember. As I recall the padding was added first, and the explanation came later. There was great dis

Keccak for xkcp and NIST for the padding, as far as I can remember. As I recall the padding was added first, and the explanation came later. There was great distrust at first during this time as a result, hence the name 'mystery padding' we used.