CODEWITHSUNDEEP
c#pythonsha1
Jon
Jon

Reputation: 217

Python hmac and C# hmac

We have a python web service. It needs a hash as a parameter. The hash in python is generated this way.

    hashed_data = hmac.new("ant", "bat", hashlib.sha1)
    print hashed_data.hexdigest()

Now, this is how I generate the hash from C#.

    ASCIIEncoding encoder = new ASCIIEncoding();
    Byte[] code = encoder.GetBytes("ant");
    HMACSHA1 hmSha1 = new HMACSHA1(code);
    Byte[] hashMe = encoder.GetBytes("bat");
    Byte[] hmBytes = hmSha1.ComputeHash(hashMe);
    Console.WriteLine(Convert.ToBase64String(hmBytes));

However, I'm coming out with different result.

Should I change the order of the hashing?

Thank you,

Jon

Upvotes: 9

Views: 5143

Answers (2)

Oskar
Oskar

Reputation: 2083

Instead of writing your own implementation to convert byte[] to a hex string, now you can get the same output as in Python using built in methods:

public static string ComputeHMACSHA256HexString(string key, string s)
{
    var hashValue = HMACSHA256.HashData(
        Encoding.UTF8.GetBytes(key),
        Encoding.UTF8.GetBytes(s));

    return BitConverter
        .ToString(hashValue)
        .Replace("-", "")
        .ToLower();
}

Upvotes: 0

Darin Dimitrov
Darin Dimitrov

Reputation: 1038710

In order to print the result:

  • In Python you use: .hexdigest()
  • In C# you use: Convert.ToBase64String

Those 2 functions don't do the same thing at all. Python's hexdigest simply converts the byte array to a hex string whereas the C# method uses Base64 encoding to convert the byte array. So to get the same output simply define a function:

public static string ToHexString(byte[] array)
{
    StringBuilder hex = new StringBuilder(array.Length * 2);
    foreach (byte b in array)
    {
        hex.AppendFormat("{0:x2}", b);
    }
    return hex.ToString();
}

and then:

ASCIIEncoding encoder = new ASCIIEncoding();
Byte[] code = encoder.GetBytes("ant");
HMACSHA1 hmSha1 = new HMACSHA1(code);
Byte[] hashMe = encoder.GetBytes("bat");
Byte[] hmBytes = hmSha1.ComputeHash(hashMe);
Console.WriteLine(ToHexString(hmBytes));

Now you will get the same output as in Python:

739ebc1e3600d5be6e9fa875bd0a572d6aee9266

Upvotes: 22

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