Hi Maik,
Have you tried to put "false" instead of "true" here?
Console.WriteLine(Convert.ToBase64String(cryptoServiceProvider.Encrypt(Encoding.Default.GetBytes(value), true)));
"true" means for OAEP (and I think my implementation is not fully interoperable) and "false" means for PKCS#1 v1.5.
I am working to fix the bug on my OAEP implementation.
Best regards,
Marion