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

Lemma RFC4231_Section4_2_hex: (*called PRF-1 in RFC4868*) checkHex "0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b" "4869205468657265" "b0344c61d8db38535ca8afceaf0bf12b881dc200c9833da726e9376c2e32cff7".