(*Test with a truncation of output to 128 bits, ie the first 16 bytes*)
Definition checkHexTrunc password text digest := 
  bytelist_eq (firstn 16 (HMACHex text password)) (hexstring_to_bytelist digest) = true.

Lemma RFC6868_exampleAUTH256_2: checkHex "4a6566654a6566654a6566654a6566654a6566654a6566654a6566654a656665" "7768617420646f2079612077616e7420666f72206e6f7468696e673f" "167f928588c5cc2eef8e3093caa0e87c9ff566a14794aa61648d81621a2a40c6".