Python hmac 在 c#

Question

This is the python code which I have to convert in c#

   ms = "ninoingfbf"
    key = "AgQGCAoMDhASFA=="
    h = hmac.new(key.encode('utf-8'), ms.encode('utf-8'),
     hashlib.sha256).hexdigest().lower()
    print( h )

I was trying the below c# code, but I am getting different results

 string msg = "ninoingfbf";
  string keystring = "AgQGCAoMDhASFA==";
  byte[] key = Convert.FromBase64String(keystring);
  HMACSHA256 hmac = new(key);
  byte[] hash = hmac.ComputeHash(Encoding.UTF8.GetBytes(msg));
  var j = BitConverter.ToString(hash).Replace("-", "").ToLower();
   return Ok(j);

Python output = "10d46c65b51ddbb1f3346dca71ca30f139a473dece78dc567f404fdc4ee49e51"

c# output = "2980906b9e1933357db6fc6b791d2d43564555a949667cc9525eff037466add0"

Answer 1

The Python code is wrong. It doesn't decode the BASE64 key but uses it as if it was the actual key. The key must be decoded using the base64 library, not encoded as UTF-8.

Strings in Python3 are Unicode and the default encoding is utf-8 , so there's no need to explicitly specify it.

The following code returns the same hash as the C# code:

import base64
import hash
import hashlib

ms = "ninoingfbf"
key = "AgQGCAoMDhASFA=="

h=hmac.new(base64.b64decode(key),ms.encode(),hashlib.sha256)

print (h.hexdigest())

This returns

2980906b9e1933357db6fc6b791d2d43564555a949667cc9525eff037466add0

Which is identical to the C# output

2980906b9e1933357db6fc6b791d2d43564555a949667cc9525eff037466add0

.NET 5 added a Convert.ToHexString method, so the C# code becomes:

using System;
using System.Security.Cryptography;
using System.Text;

var msg = "ninoingfbf";
var key = "AgQGCAoMDhASFA==";

HMACSHA256 hmac = new(Convert.FromBase64String(key));
var h = hmac.ComputeHash(Encoding.UTF8.GetBytes(msg));

Console.WriteLine(Convert.ToHexString(h).ToLower());

If you want to save the hash text for comparison you can get rid of ToLower() and use a case-insensitive comparison. In C# you can use one of the String.Compare overloads that ignores case, eg:

var areEqual=String.Compare(hash1,hash2,true);