title: Sha256 hash in Portable Library .Net
body: <p>I need to compute the hash of a byte array in a Portable Library.</p>
  
  <p>I'm trying to find an equivalent of System.Security.Cryptography.SHA256Managed for my Portable library targeting .NET 4.5 + win 8 + WP 8.0 .</p>
  
  <p>I tried  the PclContrib but it seems I can't install it for a library targeting those platforms.</p>
  
  <p>Is there any library providing hash algorithms implementations which can be referenced in the context of a Portable Library?</p>
  
  <p>Thanks</p>