DPAPI C# problem - Provider DLL could not be found exception

Question

I'm trying to use the DPAPI C# code found in this article.
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnnetsec/html/SecNetHT08.asp

I can call Encrypt just find and it returns the correct encrypted data.  But when I try and call Decrypt it throws the exception b/c of these lines of code:

retVal = CryptUnprotectData(ref cipherBlob, null, ref
                entropyBlob,
               IntPtr.Zero, ref prompt, dwFlags,
               ref plainTextBlob);
if(false == retVal) {
        throw new Exception("Decryption failed. " +
        GetErrorMessage(Marshal.GetLastWin32Error()));
}

Basically CryptUnprotectedData is returning false.  Any ideas?

Answer 1

Also, I'm using .NET 1.1.  I cannot use 2.0.