using System;
using System.Security.Cryptography;

class RSASample
{
    public static string Base64Encode(byte[] plainTextBytes) {
        return System.Convert.ToBase64String(plainTextBytes);
    }

    static void Main()
    {
        try
        {
            //Create a new instance of RSA.
            using (RSA rsa = RSA.Create())
            {
                //The hash to sign.
                byte[] hash;
                using (SHA256 sha256 = SHA256.Create())
                {
                    byte[] data = System.Text.Encoding.UTF8.GetBytes("hello world!");
                    hash = sha256.ComputeHash(data);
                }
                
                String publicKey = rsa.ToXmlString(false);
                String privateKey = rsa.ToXmlString(true);

                //Create an RSASignatureFormatter object and pass it the 
                //RSA instance to transfer the key information.
                RSAPKCS1SignatureFormatter RSAFormatter = new RSAPKCS1SignatureFormatter(rsa);

                //Set the hash algorithm.
                RSAFormatter.SetHashAlgorithm("SHA256");

                //Create a signature for HashValue and return it.
                byte[] SignedHash = RSAFormatter.CreateSignature(hash);
                
                Console.WriteLine("Public Key:");
                Console.WriteLine(publicKey);
                Console.WriteLine("Private Key:");
                Console.WriteLine(privateKey);
                
                Console.WriteLine("Sign:");
                Console.WriteLine(Base64Encode(SignedHash));
            }
        }
        catch (CryptographicException e)
        {
            Console.WriteLine(e.Message);
        }
    }
}