HMAC-SHA256 Algorithm for signature calculation

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");
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

Java simple code to generate encoded(HMAC-x) signatures. (Tried using Java-8 and Eclipse)

import java.io.UnsupportedEncodingException;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;

import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;

import com.sun.org.apache.xml.internal.security.utils.Base64;

/**
 * Encryption class to show how to generate encoded(HMAC-x) signatures.
 * 
 */
public class Encryption {

    public static void main(String args[]) {

        String message = "This is my message.";
        String key = "your_key";
        String algorithm = "HmacMD5";  // OPTIONS= HmacSHA512, HmacSHA256, HmacSHA1, HmacMD5

        try {

            // 1. Get an algorithm instance.
            Mac sha256_hmac = Mac.getInstance(algorithm);

            // 2. Create secret key.
            SecretKeySpec secret_key = new SecretKeySpec(key.getBytes("UTF-8"), algorithm);

            // 3. Assign secret key algorithm.
            sha256_hmac.init(secret_key);

            // 4. Generate Base64 encoded cipher string.
            String hash = Base64.encode(sha256_hmac.doFinal(message.getBytes("UTF-8")));

            // You can use any other encoding format to get hash text in that encoding.
            System.out.println(hash);

            /**
             * Here are the outputs for given algorithms:-
             * 
             * HmacMD5 = hpytHW6XebJ/hNyJeX/A2w==
             * HmacSHA1 = CZbtauhnzKs+UkBmdC1ssoEqdOw=
             * HmacSHA256 =gCZJBUrp45o+Z5REzMwyJrdbRj8Rvfoy33ULZ1bySXM=
             * HmacSHA512 = OAqi5yEbt2lkwDuFlO6/4UU6XmU2JEDuZn6+1pY4xLAq/JJGSNfSy1if499coG1K2Nqz/yyAMKPIx9C91uLj+w==
             */

        } catch (NoSuchAlgorithmException e) {

            e.printStackTrace();

        } catch (UnsupportedEncodingException e) {

            e.printStackTrace();

        } catch (InvalidKeyException e) {

            e.printStackTrace();

        }

    }

}

NOTE: You can use any other encryption instead of Base64 (eg: ASCII). Also you can try generating HmacMD5, HmacSHA1, HmacSHA256, HmacSHA512 signatures.

Answer 2

Try this

Sorry for being late, I have tried all above answers but none of them is giving me correct value, After doing the lot of R&D I have found a simple way that gives me exact value.

1. Declare this method in your class

   private String hmacSha(String KEY, String VALUE, String SHA_TYPE) {
   try {
       SecretKeySpec signingKey = new SecretKeySpec(KEY.getBytes("UTF-8"), SHA_TYPE);
       Mac mac = Mac.getInstance(SHA_TYPE);
       mac.init(signingKey);
       byte[] rawHmac = mac.doFinal(VALUE.getBytes("UTF-8"));
       byte[] hexArray = {(byte)'0', (byte)'1', (byte)'2', (byte)'3', (byte)'4', (byte)'5', (byte)'6', (byte)'7', (byte)'8', (byte)'9', (byte)'a', (byte)'b', (byte)'c', (byte)'d', (byte)'e', (byte)'f'};
       byte[] hexChars = new byte[rawHmac.length * 2];
       for ( int j = 0; j < rawHmac.length; j++ ) {
           int v = rawHmac[j] & 0xFF;
           hexChars[j * 2] = hexArray[v >>> 4];
           hexChars[j * 2 + 1] = hexArray[v & 0x0F];
       }
       return new String(hexChars);
   }
   catch (Exception ex) {
       throw new RuntimeException(ex);
   }
   

   }

2. Use this like

   Log.e("TAG", "onCreate: "+hmacSha("key","text","HmacSHA256"));
   

Verification

1.Android studio output 2. Online HMAC generator Output(Visit here for Online Genrator)

Answer 3

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.

Answer 4

Here is my solution:

public static String encode(String key, String data) throws Exception {
  Mac sha256_HMAC = Mac.getInstance("HmacSHA256");
  SecretKeySpec secret_key = new SecretKeySpec(key.getBytes("UTF-8"), "HmacSHA256");
  sha256_HMAC.init(secret_key);

  return Hex.encodeHexString(sha256_HMAC.doFinal(data.getBytes("UTF-8")));
}

public static void main(String [] args) throws Exception {
  System.out.println(encode("key", "The quick brown fox jumps over the lazy dog"));
}

Or you can return the hash encoded in Base64:

Base64.encodeBase64String(sha256_HMAC.doFinal(data.getBytes("UTF-8")));

The output in hex is as expected:

f7bc83f430538424b13298e6aa6fb143ef4d59a14946175997479dbc2d1a3cd8

Answer 5

This is working fine for me

I have add dependency

compile 'commons-codec:commons-codec:1.9'

ref: http://mvnrepository.com/artifact/commons-codec/commons-codec/1.9

my function

public String encode(String key, String data) {
    try {

        Mac sha256_HMAC = Mac.getInstance("HmacSHA256");
        SecretKeySpec secret_key = new SecretKeySpec(key.getBytes("UTF-8"), "HmacSHA256");
        sha256_HMAC.init(secret_key);

        return new String(Hex.encodeHex(sha256_HMAC.doFinal(data.getBytes("UTF-8"))));

    } catch (NoSuchAlgorithmException e) {
        e.printStackTrace();
    } catch (InvalidKeyException e) {
        e.printStackTrace();
    } catch (UnsupportedEncodingException e) {
        e.printStackTrace();
    }

    return null;
}

Answer 6

If but any chance you found a solution how to calculate HMAC-SHA256 here, but you're getting an exception like this one:

java.lang.NoSuchMethodError: No static method encodeHexString([B)Ljava/lang/String; in class Lorg/apache/commons/codec/binary/Hex; or its super classes (declaration of 'org.apache.commons.codec.binary.Hex' appears in /system/framework/org.apache.http.legacy.boot.jar)

Then use:

public static String encode(String key, String data) {
    try {
        Mac hmac = Mac.getInstance("HmacSHA256");
        SecretKeySpec secret_key = new SecretKeySpec(key.getBytes("UTF-8"), "HmacSHA256");
        hmac.init(secret_key);
        return new String(Hex.encodeHex(hmac.doFinal(data.getBytes("UTF-8"))));
    } catch (Exception e) {
        throw new RuntimeException(e);
    }
}