title: System.Security.Cryptography.MACTripleDES() is not defined in .NET Standard
body: <p>I am converting a vb.net library to .NET Standard and I am getting 'System.Security.Cryptography.MACTripleDES is not defined' </p>
  
  <pre><code>Imports System.Security.Cryptography  
  
  Shared Function Encode(ByVal value As String, _
                         ByVal key As String) As String
      Dim mac3des As New System.Security.Cryptography.MACTripleDES()
      Dim md5 As New System.Security.Cryptography.MD5CryptoServiceProvider()
      mac3des.Key = md5.ComputeHash(System.Text.Encoding.UTF8.GetBytes(key))
      Return Convert.ToBase64String( _
        System.Text.Encoding.UTF8.GetBytes(value)) &amp; "-"c &amp; _
        Convert.ToBase64String(mac3des.ComputeHash( _
        System.Text.Encoding.UTF8.GetBytes(value)))
  End Function
  </code></pre>
  
  <p>Is there a way to fix this as it didn't generate an error in the 4.7.1 framework library</p>
  
  <p>Thank you so much in advance</p>