using System;

using System.Security.Cryptography;

​

public class RsaEncryptionPkcs1String {

    public static void Main() {

​

    Console.WriteLine("RSA signature string");

    string dataToSignString = "The quick brown fox jumps over the lazy dog";

        byte[] dataToSign = System.Text.Encoding.UTF8.GetBytes(dataToSignString);

    Console.WriteLine("dataToSign: " + dataToSignString);

    try {

        Console.WriteLine("\n* * * sign the plaintext with the RSA private key * * *");

        string privateRsaKeyPem = loadRsaPrivateKeyPem();

        Console.WriteLine("used private key:\n" + privateRsaKeyPem);

        string signatureBase64 = rsaSignToBase64(privateRsaKeyPem, dataToSign);

        Console.WriteLine("\nsignature (Base64): " + signatureBase64);

​

        Console.WriteLine("\n* * * verify the signature against the plaintext with the RSA public key * * *");

        string publicRsaKeyPem = loadRsaPublicKeyPem();

        Console.WriteLine("used public key:\n" + publicRsaKeyPem);

        bool signatureVerified = rsaVerifySignatureFromBase64(publicRsaKeyPem, dataToSign, signatureBase64);

        if (signatureVerified) {

                  Console.WriteLine("\nsignature (Base64) verified: true");

              } else {

                  Console.WriteLine("\nsignature (Base64) verified: false");

            }

        }

        catch(ArgumentNullException) {

            Console.WriteLine("The data was not signed or verified");

        }       

    }

​

    private static string rsaSignToBase64(string privateKeyPem, byte[] dataToSign) {

      try {

        // getting the rsa private key from pem

        RSA rsaAlgd = RSA.Create();

        byte[] privateKeyByte = getRsaPrivateKeyEncodedFromPem(privateKeyPem);

        int _out;

        rsaAlgd.ImportPkcs8PrivateKey(privateKeyByte, out _out);

        //return Base64Encoding(rsaAlgd.SignData(dataToSign, new SHA256CryptoServiceProvider()));

        return Base64Encoding(rsaAlgd.SignData(dataToSign, HashAlgorithmName.SHA256, RSASignaturePadding.Pkcs1));

        //return Base64Encoding(rsaAlgd.SignData(dataToSign, new SHA256CryptoServiceProvider()));

        } catch(CryptographicException e) {

            Console.WriteLine(e.Message);

            return null;

        }

  }

​

  private static bool rsaVerifySignatureFromBase64(string publicKeyPem, byte[] dataToSign, string signatureBase64) {

      try {

        var signature = Base64Decoding(signatureBase64);

        // getting the rsa public key from pem

        RSA rsaAlg = RSA.Create();

        rsaAlg.ImportFromPem(publicKeyPem);

        return rsaAlg.VerifyData(dataToSign, signature, HashAlgorithmName.SHA256, RSASignaturePadding.Pkcs1);

      } catch(CryptographicException e) {

            Console.WriteLine(e.Message);

            return false;

        }

  } 

​

    static string Base64Encoding(byte[] input) {

        return Convert.ToBase64String(input);

    }

​

    static byte[] Base64Decoding(String input) {

        return Convert.FromBase64String(input);

    }

​

    private static byte[] getRsaPrivateKeyEncodedFromPem(string rsaPrivateKeyPem) {

        string rsaPrivateKeyHeaderPem = "-----BEGIN PRIVATE KEY-----\n";

        string rsaPrivateKeyFooterPem = "-----END PRIVATE KEY-----";

        string rsaPrivateKeyDataPem = rsaPrivateKeyPem.Replace(rsaPrivateKeyHeaderPem, "").Replace(rsaPrivateKeyFooterPem, "").Replace("\n", "");

        return Base64Decoding(rsaPrivateKeyDataPem);

    }

​

    private static string loadRsaPrivateKeyPem() {

        // this is a sample key - don't worry !

        return "-----BEGIN PRIVATE KEY-----\n" + 

            "MIIEvgIBADANBgkqhkiG9w0BAQEFAASCBKgwggSkAgEAAoIBAQDwSZYlRn86zPi9\n" + 

            "e1RTZL7QzgE/36zjbeCMyOhf6o/WIKeVxFwVbG2FAY3YJZIxnBH+9j1XS6f+ewjG\n" + 

            "FlJY4f2IrOpS1kPiO3fmOo5N4nc8JKvjwmKtUM0t63uFFPfs69+7mKJ4w3tk2mSN\n" + 

            "4gb8J9P9BCXtH6Q78SdOYvdCMspA1X8eERsdLb/jjHs8+gepKqQ6+XwZbSq0vf2B\n" + 

            "MtaAB7zTX/Dk+ZxDfwIobShPaB0mYmojE2YAQeRq1gYdwwO1dEGk6E5J2toWPpKY\n" + 

            "/IcSYsGKyFqrsmbw0880r1BwRDer4RFrkzp4zvY+kX3eDanlyMqDLPN+ghXT1lv8\n" + 

            "snZpbaBDAgMBAAECggEBAIVxmHzjBc11/73bPB2EGaSEg5UhdzZm0wncmZCLB453\n" + 

            "XBqEjk8nhDsVfdzIIMSEVEowHijYz1c4pMq9osXR26eHwCp47AI73H5zjowadPVl\n" + 

            "uEAot/xgn1IdMN/boURmSj44qiI/DcwYrTdOi2qGA+jD4PwrUl4nsxiJRZ/x7PjL\n" + 

            "hMzRbvDxQ4/Q4ThYXwoEGiIBBK/iB3Z5eR7lFa8E5yAaxM2QP9PENBr/OqkGXLWV\n" + 

            "qA/YTxs3gAvkUjMhlScOi7PMwRX9HsrAeLKbLuC1KJv1p2THUtZbOHqrAF/uwHaj\n" + 

            "ygUblFaa/BTckTN7PKSVIhp7OihbD04bSRrh+nOilcECgYEA/8atV5DmNxFrxF1P\n" + 

            "ODDjdJPNb9pzNrDF03TiFBZWS4Q+2JazyLGjZzhg5Vv9RJ7VcIjPAbMy2Cy5BUff\n" + 

            "EFE+8ryKVWfdpPxpPYOwHCJSw4Bqqdj0Pmp/xw928ebrnUoCzdkUqYYpRWx0T7YV\n" + 

            "RoA9RiBfQiVHhuJBSDPYJPoP34kCgYEA8H9wLE5L8raUn4NYYRuUVMa+1k4Q1N3X\n" + 

            "Bixm5cccc/Ja4LVvrnWqmFOmfFgpVd8BcTGaPSsqfA4j/oEQp7tmjZqggVFqiM2m\n" + 

            "J2YEv18cY/5kiDUVYR7VWSkpqVOkgiX3lK3UkIngnVMGGFnoIBlfBFF9uo02rZpC\n" + 

            "5o5zebaDImsCgYAE9d5wv0+nq7/STBj4NwKCRUeLrsnjOqRriG3GA/TifAsX+jw8\n" + 

            "XS2VF+PRLuqHhSkQiKazGr2Wsa9Y6d7qmxjEbmGkbGJBC+AioEYvFX9TaU8oQhvi\n" + 

            "hgA6ZRNid58EKuZJBbe/3ek4/nR3A0oAVwZZMNGIH972P7cSZmb/uJXMOQKBgQCs\n" + 

            "FaQAL+4sN/TUxrkAkylqF+QJmEZ26l2nrzHZjMWROYNJcsn8/XkaEhD4vGSnazCu\n" + 

            "/B0vU6nMppmezF9Mhc112YSrw8QFK5GOc3NGNBoueqMYy1MG8Xcbm1aSMKVv8xba\n" + 

            "rh+BZQbxy6x61CpCfaT9hAoA6HaNdeoU6y05lBz1DQKBgAbYiIk56QZHeoZKiZxy\n" + 

            "4eicQS0sVKKRb24ZUd+04cNSTfeIuuXZrYJ48Jbr0fzjIM3EfHvLgh9rAZ+aHe/L\n" + 

            "84Ig17KiExe+qyYHjut/SC0wODDtzM/jtrpqyYa5JoEpPIaUSgPuTH/WhO3cDsx6\n" + 

            "3PIW4/CddNs8mCSBOqTnoaxh\n" + 

            "-----END PRIVATE KEY-----";

    }

​

    private static string loadRsaPublicKeyPem() {

        // this is a sample key - don't worry !

        return "-----BEGIN PUBLIC KEY-----\n" + 

            "MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA8EmWJUZ/Osz4vXtUU2S+\n" + 

            "0M4BP9+s423gjMjoX+qP1iCnlcRcFWxthQGN2CWSMZwR/vY9V0un/nsIxhZSWOH9\n" + 

            "iKzqUtZD4jt35jqOTeJ3PCSr48JirVDNLet7hRT37Ovfu5iieMN7ZNpkjeIG/CfT\n" + 

            "/QQl7R+kO/EnTmL3QjLKQNV/HhEbHS2/44x7PPoHqSqkOvl8GW0qtL39gTLWgAe8\n" + 

            "01/w5PmcQ38CKG0oT2gdJmJqIxNmAEHkatYGHcMDtXRBpOhOSdraFj6SmPyHEmLB\n" + 

            "ishaq7Jm8NPPNK9QcEQ3q+ERa5M6eM72PpF93g2p5cjKgyzzfoIV09Zb/LJ2aW2g\n" + 

            "QwIDAQAB\n" + 

            "-----END PUBLIC KEY-----";

    }

}