Question

I am trying to create a signature using the HMAC-SHA256 algorithm and this is my code.
I am using US ASCII encoding.

final Charset asciiCs = Charset.forName("US-ASCII");
final Mac sha256_HMAC = Mac.getInstance("HmacSHA256");
final SecretKeySpec secret_key = new javax.crypto.spec.SecretKeySpec(asciiCs.encode("key").array(), "HmacSHA256");
sha256_HMAC.init(secret_key);
final byte[] mac_data = sha256_HMAC.doFinal(asciiCs.encode("The quick brown fox jumps over the lazy dog").array());
String result = "";
for (final byte element : mac_data)
{
    result += Integer.toString((element & 0xff) + 0x100, 16).substring(1);
}
System.out.println("Result:[" + result + "]");

The result that I am getting from the above code is:

f7bc83f430538424b13298e6aa6fb143ef4d59a14946175997479dbc2d1a3cd8

This is same as to that of shown in the wiki

HMAC_SHA256("key", "The quick brown fox jumps over the lazy dog") = 0x f7bc83f430538424b13298e6aa6fb143ef4d59a14946175997479dbc2d1a3cd8

except for the 0x.

I am looking for ideas/comments if I am doing everything right or may be I can improve my code.

Answer 1

The 0x just denotes that the characters after it represent a hex string.

0x1A == 1Ah == 26 == 1A

So the 0x is just to clarify what format the output is in, no need to worry about it.