HMAC-SHA256 Algorithm for signature calculation

JavaCharacter EncodingDigital SignatureHmac

Java Problem Overview

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.

Java Solutions

Solution 1 - Java

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

Solution 2 - Java

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.

Solution 3 - Java

If you're using Guava, its latest release now lets you use

 Hashing.hmacSha256()

One example of using this:

String hash = Hashing.hmacSha256("mykey".getBytes(StandardCharsets.UTF_8)).hashString("my_message", StandardCharsets.UTF_8).toString()

Further documentation here: https://guava.dev/releases/23.0/api/docs/com/google/common/hash/Hashing.html#hmacSha256-byte:A-

Solution 4 - Java

The answer that you got there is correct. One minor thing in the code above, you need to init(key) before you can call doFinal()

    final Charset charSet = Charset.forName("US-ASCII");
    final Mac sha256_HMAC = Mac.getInstance("HmacSHA256");
    
    final SecretKeySpec secret_key = new javax.crypto.spec.SecretKeySpec(charSet.encode("key").array(), "HmacSHA256");
    try {
		sha256_HMAC.init(secret_key);
	} catch (InvalidKeyException e) {
		// TODO Auto-generated catch block
		e.printStackTrace();
	}
    ...

Solution 5 - Java

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(StandardCharsets.UTF_8), "HmacSHA256");
        sha256_HMAC.init(secret_key);

        return Hex.encodeHexString(sha256_HMAC.doFinal(data.getBytes(StandardCharsets.UTF_8)));

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

Solution 6 - Java

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 Android studio output

  1. Online HMAC generator Output(Visit here for Online Genrator) enter image description here

Solution 7 - Java

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 Algorithms and can try generating HmacMD5, HmacSHA1, HmacSHA256, HmacSHA512 signatures.

Solution 8 - Java

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);
    }
}

Solution 9 - Java

Here is my solution:

public String HMAC_SHA256(String secret, String message)
{
    String hash="";
    try{
        Mac sha256_HMAC = Mac.getInstance("HmacSHA256");
        SecretKeySpec secret_key = new SecretKeySpec(secret.getBytes(), "HmacSHA256");
        sha256_HMAC.init(secret_key);

        hash = Base64.encodeToString(sha256_HMAC.doFinal(message.getBytes()), Base64.DEFAULT);
    }catch (Exception e)
    {

    }
    return hash.trim();
}
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