Cannot get same hash in C# as in python

Question

I have a string that I need to hash in order to access an API. The API-creator has provided a codesnippet in Python, which hashes the code like this:

hashed_string = hashlib.sha1(string_to_hash).hexdigest()

When using this hashed string to access the API, everything is fine. I have tried to get the same hashed string result in C#, but without success. I have tried incredibly many ways but nothing has worked so far. I am aware about the hexdigest part aswell and I have kept that in mind when trying to mimic the behaviour.

Does anyone know how to get the same result in C#?

EDIT: This is one of the many ways I have tried to reproduce the same result in C#:

public string Hash(string input)
{
    using (SHA1Managed sha1 = new SHA1Managed())
    {
        var hash = sha1.ComputeHash(Encoding.UTF8.GetBytes(input));
        var sb = new StringBuilder(hash.Length * 2);

        foreach (byte b in hash)
        {
            sb.Append(b.ToString("X2"));
        }

        return sb.ToString().ToLower();
    }
}

This code is taken from: Hashing with SHA1 Algorithm in C#

Another way

public string ToHexString(string myString)
{
    HMACSHA1 hmSha1 = new HMACSHA1();
    Byte[] hashMe = new ASCIIEncoding().GetBytes(myString);
    Byte[] hmBytes = hmSha1.ComputeHash(hashMe);
    StringBuilder hex = new StringBuilder(hmBytes.Length * 2);
    foreach (byte b in hmBytes)
    {
        hex.AppendFormat("{0:x2}", b);
    }
    return hex.ToString();
}

This code is taken from: Python hmac and C# hmac

EDIT 2

Some input/output:

C# (using second method provided in above description)

input: callerId1495610997apiKey3*_&E#N@B1)O)-1Y

output: 1ecded2b66e152f0965adb96727d96b8f5db588a

Python

input: callerId1495610997apiKey3*_&E#N@B1)O)-1Y

output: bf11a12bbac84737a39152048e299fa54710d24e

C# (using first method provided in above description)

input: callerId1495611935apiKey{[B{+%P)s;WD5&5x

output: 7e81e0d40ff83faf1173394930443654a2b39cb3

Python

input: callerId1495611935apiKey{[B{+%P)s;WD5&5x

output: 512158bbdbc78b1f25f67e963fefdc8b6cbcd741

Please show a minimal reproducible example - my guess is that there's a bug in your C# code, but as we can't see any of your C# code, it's hard to tell. — Jon Skeet
– Jon Skeet, Commented May 24, 2017 at 7:17
You didn't bother including the results of your first C# code, which is the same as your python results, just in upper case... — Jon Skeet
– Jon Skeet, Commented May 24, 2017 at 7:44
As noted in comments on Federico's answer, you've got a non-ascii character in the input for the bottom two examples. I suspect that's not meant to be there, is it? — Jon Skeet
– Jon Skeet, Commented May 24, 2017 at 8:23
Please take note that if you'd provided a minimal reproducible example from the start, you may well have found the problem before even hitting "Post". Worth remembering for next time... — Jon Skeet
– Jon Skeet, Commented May 24, 2017 at 9:23

Federico Dipuma · Accepted Answer · 2017-05-24 08:33:48Z

7

C#:

public static string Hash(string input)
{
    using (SHA1Managed sha1 = new SHA1Managed())
    {
        var hash = sha1.ComputeHash(Encoding.UTF8.GetBytes(input));
        var sb = new StringBuilder(hash.Length * 2);

        foreach (byte b in hash)
        {
            sb.Append(b.ToString("x2")); // x2 is lowercase
        }

        return sb.ToString().ToLower();
    }
}

public static void Main()
{
    var x  ="callerId1495611935apiKey{[B{+%P)s;WD5&5x";
    Console.WriteLine(Hash(x)); // prints 7e81e0d40ff83faf1173394930443654a2b39cb3
}

Python

import hashlib
s = u'callerId1495611935apiKey{[B{+%P)s;WD5&5x'
enc = s.encode('utf-8') # encode in utf8
hash = hashlib.sha1(enc)
formatted = h.hexdigest()
print(formatted) # prints 7e81e0d40ff83faf1173394930443654a2b39cb3

Your main problem is that you are using different encodings for the same string in C# and Python. Use UTF8 in both languages and use the same casing. The output is the same.

Note that inside your input string (between callerId1495611935 and apiKey{[B{+%P)s;WD5&5x) there is an hidden \u200b character. That's why encoding your string in UTF-8 gives a different result than encoding it using ASCII. Does that character have to be inside your string?

edited May 24, 2017 at 8:33

answered May 24, 2017 at 8:10

Federico Dipuma

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6 Comments

Jon Skeet Over a year ago

I'm all for being explicit in general, but on my box at least it makes no difference (which is what I'd expect, given that the input is all-ASCII). hashlib.sha1(s).hexdigest() gives the same result.

Federico Dipuma Over a year ago

@JonSkeet If you try to copy and paste OP original input string you'll notice that between callerId1495611935 and apiKey{[B{+%P)s;WD5&5x there is an hidden \u200b character (don't ask me why).

Jon Skeet Over a year ago

Urgh - well spotted. that would explain things. I suspect that shouldn't be in the input.

Federico Dipuma Over a year ago

@JonSkeet I agree.

Markus Olsson Over a year ago

Thanks so much for this, very good catch! And thanks JonSkeet for your help aswell, i'll try to fix this. :)

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