Error when converting Flash to C#

I have the following method in Flash which writes two ByteArrays and then base64 encodes them

private function generateSignature(data:String, secretKey:String):String {             
    var secretKeyByteArray:ByteArray = new ByteArray();
    secretKeyByteArray.writeUTFBytes(secretKey);
    secretKeyByteArray.position = 0;

    var dataByteArray:ByteArray = new ByteArray();
    dataByteArray.writeUTFBytes(data);
    dataByteArray.position = 0;

    var hmac:HMAC = new HMAC(new SHA1());            
    var signatureByteArray:ByteArray = hmac.compute(secretKeyByteArray, dataByteArray);
    return Base64.encodeByteArray(signatureByteArray);
}

In my C#, I have:

string GenerateSignature(string secretKey, string base64Policy)
{
    byte[] secretBytes = Encoding.UTF8.GetBytes(secretKey);
    byte[] dataBytes = Encoding.UTF8.GetBytes(base64Policy);
    HMACSHA1 hmac = new HMACSHA1(secretBytes);
    byte[] signature = hmac.ComputeHash(dataBytes);
    return ByteToString(signature);
}

But, I get a different result set from the Flash version compared to the C# version. Can anyone spot anything that is obviously wrong?

EDIT

Here is the ByteToStrin开发者_运维知识库g method:

static string ByteToString(byte[] buffer)
{
   string binary = string.Empty;
   for (int i = 0; i < buffer.Length; i++)
   {
      binary += buffer[i].ToString("X2"); // Hex Format
   }
   return binary;
}

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It looks pretty much the same; that said, I would suggest using Convert.ToBase64String instead of your ByteToString method, the string concatenation in there is generally considered very bad practice.

I am also not 100% sure if Base 64 encoding is logically the same as appending byte.ToString("X2") for each byte to a string (although it could well be).

Other than that, it shouldn't be too difficult to debug and figure out where the two start to deviate...

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Your ByteToString function merely returns a hexadecimal version of the signature. Your flash version base 64 encodes it. There's a big difference between converting something to a hexadecimal string, and base 64 encoding.

Use Convert.ToBase64String instead of ByteToString.

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Flash might not be emitting the BOM (Byte Order Mark), where C# (.Net) does.

public static readonly Encoding Utf8NoBom = new UTF8Encoding(false);

According to the Flash Documentation you are using the correct encoding on the C# end; so this is the only possible alternative (it didn't have anything to say about the BOM).