docs: public Packer useHMAC(final String hMacAlg, final String passphrase) throws NoSuchAlgorithmException,
  			InvalidKeyException {
  		hMac = Mac.getInstance(hMacAlg); // "HmacSHA256"
  		hMac.init(new SecretKeySpec(passphrase.getBytes(charsetUTF8), hMacAlg));
  		return this;
  	}