Definition checkHex password text digest :=
  bytelist_eq (HMACHex text password) (hexstring_to_bytelist digest) = true.

Lemma RFC4231_Section4_5_hex: (*called PRF-4 in RFC4868*) checkHex "0102030405060708090a0b0c0d0e0f10111213141516171819" "cdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcd" "82558a389a443c0ea4cc819899f2083a85f0faa3e578f8077a2e3ff46729665b".