It would help to test your code before posting it. You haven't imported javax.crypto.Mac, so it won't compile. Also, your conversion from strings to bytes and

It would help to test your code before posting it. You haven't imported javax.crypto.Mac, so it won't compile. Also, your conversion from strings to bytes and back is just wrong - this will not work as expected when run on machines with a different platform encoding. This is a real problem when writing security code - I've seen code that attempted to get the bytes from passwords on a japanese website in ISO-8859-1, effectively making all passwords of the same length the same value. // get bytes in UTF-8 - always supported in java // as its specified in the JLS, and supports every // code point that can appear in the string byte[] secretByte = macKey.getBytes("UTF-8"); byte[] dataBytes = macData.getBytes("UTF-8"); SecretKey secret = new SecretKeySpec(secretByte, "HMACSHA256"); mac.init(secret); byte[] doFinal = mac.doFinal(dataBytes); // Hex supplies a method to get a string directly. Use it. String checksum = Hex.encodeHex(doFinal);