using System;

using System.Security.Cryptography;

using System.Text;

​

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);

    string passphrase = "123456";       

    try {

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

        string privateRsaKeyPem = loadRsaPrivateKeyEncryptedPem();

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

        string signatureBase64 = rsaSignToBase64(privateRsaKeyPem, passphrase, 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, string passphrase, byte[] dataToSign) {

      try {

        // getting the rsa private key from pem

        RSA rsaAlgd = RSA.Create();

        byte[] privateKeyByte = getRsaPrivateKeyEncryptedEncodedFromPem(privateKeyPem);

        int _out;

        rsaAlgd.ImportEncryptedPkcs8PrivateKey(passphrase, privateKeyByte, out _out);

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

        } 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[] getRsaPrivateKeyEncryptedEncodedFromPem(string rsaPrivateKeyPem) {

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

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

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

        return Base64Decoding(rsaPrivateKeyDataPem);

    }   

​

    private static string loadRsaPrivateKeyEncryptedPem() {

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

        // passphrase for decryption: 123456

        // passphrase scheme: PBES2

        // password based key derivation: PBKDF2 with HMAC and SHA-256

        // encryption algorithm: AES256-CBC

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

                "MIIFLTBXBgkqhkiG9w0BBQ0wSjApBgkqhkiG9w0BBQwwHAQIUo/aHb7/5jUCAggA\n" +

                "MAwGCCqGSIb3DQIJBQAwHQYJYIZIAWUDBAEqBBCbpiqeplyyDN85uu5yYqpFBIIE\n" +

                "0Iqvy2v42HeASj6B25llJjNOWvT5djjDiAg7BFsuOhMq10mTC7gWduXBai5llUBH\n" +

                "qF4+GgqCeedwT24YkdR4wAqtc2shcmq+2xC70N/XrSg9geGehmNwDx35byhPjouk\n" +

                "XwA5tgVsKtxTob/xjPYhjL5J1KpWOPQhdnHPGfGlWedTyTKboRfgkZ/Yds5EW6k7\n" +

                "mO9wt/iXcym6QgaJTswa1ntGPVaKMYvXVRtNnphsI9M7njXBYO52vfujUaeKn8Xe\n" +

                "qmuEAKGFhhu+r7/WWyQl+Zq2KIoD5ImOxuXScCZVH3+76AxXSwDJzB6ZG1SowSy+\n" +

                "YHbfkmvK2H6YdFshEfI/coMmu9E3wDKuCY7rgb70lHLcpvbSMa88vCFl3d/ZfmFl\n" +

                "w4TwG3vEVR9wfbXAuAw6XTSLBODcF4ifZnyXI2Dr+fQbQd/4o8w05hDiPkXRgnYY\n" +

                "e/4nFbTGGKvatZ7LOLa62isiGtQ4nprDpTapLMeJCFSgQN1jlZMVvV6mKUfrCJ69\n" +

                "3bESlyYGAN0MAx4KeMcCRwuEXWhOkLMFW0gvRp1udiMxJ8SnWfseYTr2FPUFQlFk\n" +

                "2ZhHsSO0Pg/cszUSuCX0q2ZW0ZZOiihJsmiQNXlbsRog9m8vaxUfA00v/q6iryGE\n" +

                "ApCiQd653ikukRhk/nQEY6OV4byLyI9zESF/pIdsrFnEtGSd0tggGsREtn11D8+7\n" +

                "SW0F0Es4P4UUPjiaYzyB58gcZJWxcoq63NOTUaicvTjNbzQu1+4y+2xhFe89e09w\n" +

                "PFSGerjSV/uVtVTH2hb79mAmlyLvaikQfQq2nvpCuZy7wZjhPA3D03WFTCbrYS7P\n" +

                "PfckAICCBCIB97vPsWVAviOVOrG5NDbIag+/3YhZb2gyuR2/E0XI1NdXO63NqU9R\n" +

                "B6VUUNdSvv4djA30nVjARlh3LOZmTy50OIj/QDOEbBrtFH79eHHxHRiK0+Q0A8Ch\n" +

                "EoDDz7bMKBcpiS3vXnI2UsrZX/QIuRjypc003uVm4MvdUwv0j3UGZr9zRGctqWf0\n" +

                "YBRkoIELRA45hQn0Ln3+wjAcjLRPpeuPgVAq7tDDLDmP0i/m8UbjNorhdv4CrT/u\n" +

                "P+keTW7v9Nuov1IXG4W6wKipYRzMjiYrTL5TaXPi9z63b6RQVShAEqSTtsPg5nDy\n" +

                "CZkt5NPBltq+3InrsTlbKSQGYn6wyEQeBYezD3CLkIliDn7UM4BDn+k5YonNynU4\n" +

                "emxbU4wyBEXoMD8+aBMf+bKKQXU97Ts9p7is+Ogqyop2mbMOebIxCKayizlb7/hp\n" +

                "Qs2ThBP84OrniUEeKVAkdykZyrdCoatgXVJngDwwEkSwOrEYZ0sJ48qPQMTN3kVq\n" +

                "r5XJjX3m8mpXdz0s9VbhT/rWSdQMX82msof4c6+RghEbiHFG4B0el5vrJaAROb69\n" +

                "3OnoU8mYKBlFjbO1rJJpGS5h/v+ysqWxDxfPPLD86UsgDAjr5C7W3K8eYB1UD/wP\n" +

                "n91TuTdrLKhLE93VsCyXnsLm44Td3MBv89Fr2CMF/Jz15Nfrg3yvR7bKvkNs3uVM\n" +

                "FVO3kqtmUMC/RsUr3NIE/RZ2sS+cjLMDE2zBUgHnDpNQB6WSuwqEI9prAWxEc1jS\n" +

                "SwyNkvstftK35nfeI3FNP0R94+kSKzGmiQh5yl3ufAVi\n" +

                "-----END ENCRYPTED 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-----";

    }

}