static void Main(string[] args)
        {
            RSACipher rsa = new RSACipher();

            (var publicKey, var privateKey) = rsa.GenerateRSAPair();
            BigInteger secretText = BigInteger.Parse("13483148314831849481394811231232121");

            if (secretText > publicKey.N)
            {
                throw new Exception("Too big");
            }
            var crypt   = rsa.EncryptRSA(secretText, publicKey);
            var decrypt = rsa.DecryptRSA(crypt, privateKey);

            Console.WriteLine("text: {0}\n crypted: {1}\n decrypted: {2}", secretText, crypt, decrypt);
        }