question: public static byte [ ] generateMac ( byte [ ] byteCipherText , SecretKeySpec integrityKey ) throws NoSuchAlgorithmException , InvalidKeyException { Mac sha256_HMAC = Mac . getInstance ( HMAC_ALGORITHM ) ; sha256_HMAC . init ( integrityKey ) ; return sha256_HMAC . doFinal ( byteCipherText ) ; }
target:  Generate the mac based on HMAC_ALGORITHM