Trying to match SHA512 hashes between c# and nodejs crypto

Question

Given the following c# code.

    public static string HashSHA512( string phrase )
    {
        if( m_SHA512HashProvider == null )
            m_SHA512HashProvider = new SHA512CryptoServiceProvider();

        if ( m_HashBuffer == null )
            m_HashBuffer = new byte[512];

        int length = Encoding.ASCII.GetBytes( phrase, 0, phrase.Length > 512 ? 512 : phrase.Length, m_HashBuffer, 0 );
        byte[] hashed = m_SHA512HashProvider.ComputeHash( m_HashBuffer, 0, length );

        return BitConverter.ToString( hashed );         
    }

and the following nodejs code

  generate: function(input, cb){
    var hash = Crypto.createHash('sha512').update(input).digest('hex');
    console.log('crypto generate:', hash);
    return cb(hash);
  },

my hashes don't match up. How can I alter either side to make them match up accordingly?

Answer 1

There are multiple errors in your C# code.
Compare the following and try to figure out exactly where the faults are.

public static string HashSHA512( string phrase )
{
  if( m_SHA512HashProvider == null )
    m_SHA512HashProvider = new SHA512CryptoServiceProvider();

  byte[] hashed = m_SHA512HashProvider.ComputeHash(Encoding.UTF8.GetBytes(phrase)); // or ASCII if that's sufficient for you input data.

  return BitConverter.ToString( hashed );         
}

Some hints:

• Use UTF8 instead of ASCII (some characters might get truncated)
• GetBytes doesn't return a length of something. It returns an array of bytes.
• ComputeHash doesn't have an out or ref parameter and since m_HashBuffer contains nothing, if m_HashBuffer is null, the hash is always computed on nothing.

Edit
Looking at the node.js API it seems that in C# you need to do an additional step:

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

This is because the digest method doesn't add the hyphens and all characters are lower case.

Disclaimer: Code not tested.