Generate SHA1 Hash in Portable Class Library

Question

I'm trying to build a portable class library that generates OAuth urls for other classes/applications to use. This class library using OAuth has to be a portable class library so it can work with different versions of a DropBox API I'm building.

Part of this class needs to generate an SHA1 hash to generate the oauth_signature with.

I'm aware that portable class library doesn't support System.Security.Cryptography, so is there anyway that this class can generate an SHA1 hash without that class?

Answer 1

I think the easiest way is to use the PCLCrypto nuget package. Then you can do:

private static string CalculateSha1Hash(string input)
{
        // step 1, calculate MD5 hash from input
        var hasher = WinRTCrypto.HashAlgorithmProvider.OpenAlgorithm(HashAlgorithm.Sha1);
        byte[] inputBytes = Encoding.UTF8.GetBytes(input);
        byte[] hash = hasher.HashData(inputBytes);

        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < hash.Length; i++)
        {
            sb.Append(hash[i].ToString("X2"));
        }
        return sb.ToString();
}

Answer 2

Well I needed this too recently and I found much easier to take SHA1 implementation from HashLib : http://hashlib.codeplex.com/

Mono implementation have some far-going dependencies (localization of exceptions, etc.), while from HashLib you need only to copy few files without any changes in them:

Converters.cs
Hash.cs
HashBuffer.cs
HashCryptoNotBuildIn.cs
HashResult.cs
IHash.cs
SHA0.cs
SHA1.cs

55 KB of code total, so nothing too heavy.

Answer 3

I have used this BouncyCastle Nuget package: https://www.nuget.org/packages/BouncyCastle-PCL/ and it works just fine for me (cross platforms Windows Store App, .Net Framework 4.5, Silverlight 5, Windows Phone 8, Xamarin.Android, Xamarin.iOS)

Use HMACSHA1 to generate signature like this:

public string GenerateSignature(string key, string signatureBase)
{
   var keyBytes = Encoding.UTF8.GetBytes(key);
   HMACSHA1 hashAlgorithm = new HMACSHA1(keyBytes);            
   byte[] dataBuffer = Encoding.UTF8.GetBytes(signatureBase);
   byte[] hashBytes = hashAlgorithm.ComputeHash(dataBuffer);
   return Convert.ToBase64String(hashBytes);
}

Answer 4

Mono provides a managed implementation of SHA1 for it's own mscorlib.dll (but it's not located in Mono.Security.dll like @CodeInChaos suggested).

It's open source, very well tested and meant to behave exactly like Microsoft implementation (e.g. it derives from SHA1, HashAlgorith... implements ICryptoTransform...) so it should be an easy drop-in replacement.