Java and Python generate different Hmac-SHA256 output

Question

I am trying to generate the same Hmac-SHA256 signature in Python as in my Java template. But the Python script generates not the same output. I can not find my mistake. Can anyone help me?

Java

public class Main {
    public static void main(String[] args) {
        String paramString = "teststring";
        calculateSignature(hash(paramString));
    }

    private static byte[] hash(String paramString)
    {
        MessageDigest localMessageDigest = MessageDigest.getInstance("SHA-256");
        localMessageDigest.update(paramString.getBytes("UTF-8"));
        byte[] paramByte = localMessageDigest.digest();
        System.out.println("Hash: " + DatatypeConverter.printBase64Binary(paramByte));
        return paramByte;
    }

    public static void calculateSignature(byte[] paramArrayOfByte)
    {
        String Algor = "HmacSHA256";
        Mac localMac = Mac.getInstance(Algor);
        byte [] key = "secretkey".getBytes();
        localMac.init(new SecretKeySpec(key, Algor));
        paramArrayOfByte = localMac.doFinal(paramArrayOfByte);
        System.out.println("Signature: " + DatatypeConverter.printBase64Binary(paramArrayOfByte));
    }
}

Hash: PIcn4BmkK0RGZ6WHtgASUb7K2ruza/7YCHqSwYiC0RE=

Signature: X8V4RA7qaoVGz5K2l61gAXNPuLkAI7NZ9/9d7WnblbA=

Python

# -*- coding: utf-8 -*-
import hashlib
import base64
import hmac

secretkey = 'secretkey'
stringToSign = "teststring"

def hash(paramstring):
    x = base64.b64encode(hashlib.sha256(paramstring).digest())
    print('Hash: ' + x)
    return x

def calculate_signature(hashvalue):
    x = base64.b64encode(hmac.new(secretkey, hashvalue, hashlib.sha256).digest())
    print('Signature: ' + x)

calculate_signature(hash(stringToSign))

Hash: PIcn4BmkK0RGZ6WHtgASUb7K2ruza/7YCHqSwYiC0RE=

Signature: NE8RtuFsOtafWrwDdlzILMgqCDm2huJ9A3IO6iy44Jc=

alpert · Accepted Answer · 2016-04-24 10:13:07Z

1

The problem is in python code you return base64 encoded but in java you just print it as base64 encoded but return without.

Try:

private static byte[] hash(String paramString)
{
    MessageDigest localMessageDigest = MessageDigest.getInstance("SHA-256");
    localMessageDigest.update(paramString.getBytes("UTF-8"));
    byte[] paramByte = localMessageDigest.digest();
    String base64Binary = DatatypeConverter.printBase64Binary(paramByte);
    System.out.println("Hash: " + base64Binary);
    return base64Binary.getBytes();
}

Or modify python code as:

def hash(paramstring):
    x = hashlib.sha256(paramstring).digest()
    return x

edited Apr 24, 2016 at 10:13

answered Apr 24, 2016 at 9:20

alpert

4,6751 gold badge21 silver badges28 bronze badges

Sign up to request clarification or add additional context in comments.

6 Comments

user2534685 Over a year ago

It is right. The Hmac module in java needs a byte encoded input. Also I must adjust the python code to the java code. What is wrong in the python code?

alpert Over a year ago

Why you need to adjust python code? With these changes both python and java gives same result.

user2534685 Over a year ago

I must write the python code to communicate with a existing system. The java code works with the system and is my template.

user2534685 Over a year ago

Signature: X8V4RA7qaoVGz5K2l61gAXNPuLkAI7NZ9/9d7WnblbA=

alpert Over a year ago

So you can change python code as in answer. I updated it.

|

Collectives™ on Stack Overflow

Java and Python generate different Hmac-SHA256 output

1 Answer 1

6 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

6 Comments

Your Answer

Sign up or log in

Post as a guest

Related