How to Verify a RSA-SHA512 XML Signature in .NET?

Question

With the help of the MSDN site about SignedXml, I can easily verify if an XML DSig is correct. It works perfectly if the signature method sha1 was used.

However, whe

Answer 1

You can verfify RSA SHA512 signatures but you'll have to implement and register the signature description by yourself.

Signature description:

public sealed class RSAPKCS1SHA512SignatureDescription : SignatureDescription
{
    public RSAPKCS1SHA512SignatureDescription()
    {
        KeyAlgorithm = typeof( RSACryptoServiceProvider ).FullName;
        DigestAlgorithm = typeof( SHA512Managed ).FullName;
        FormatterAlgorithm = typeof( RSAPKCS1SignatureFormatter ).FullName;
        DeformatterAlgorithm = typeof( RSAPKCS1SignatureDeformatter ).FullName;
    }

    public override AsymmetricSignatureDeformatter CreateDeformatter( AsymmetricAlgorithm key )
    {
        if( key == null )
        {
            throw new ArgumentNullException( "key" );
        }

        var deformatter = new RSAPKCS1SignatureDeformatter( key );
        deformatter.SetHashAlgorithm( "SHA512" );
        return deformatter;
    }

    public override AsymmetricSignatureFormatter CreateFormatter( AsymmetricAlgorithm key )
    {
        if( key == null )
        {
            throw new ArgumentNullException( "key" );
        }

        var formatter = new RSAPKCS1SignatureFormatter( key );
        formatter.SetHashAlgorithm( "SHA512" );
        return formatter;
    }
}

In your code you'll have to register this description with CryptoConfig:

const string XmlDsigRsaSha512 = "http://www.w3.org/2001/04/xmldsig-more#rsa-sha512";
CryptoConfig.AddAlgorithm( typeof( RSAPKCS1SHA512SignatureDescription ), XmlDsigRsaSha512 );

I tested it with .Net 4.0 on Windows 7 64 Bit.