using System;

using System.Security.Cryptography;

using System.Text;

​

public class RsaEncryptionPkcs1String {

    public static void Main() {

        Console.WriteLine("RSA 2048 encryption PKCS 1.5 string");

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

        Console.WriteLine("plaintext: " + dataToEncryptString);

​

        // # # # usually we would load the private and public key from a file or keystore # # #

        // # # # here we use hardcoded keys for demonstration - don't do this in real programs # # #

        try {

            // encryption

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

            string publicKeyLoad = loadRsaPublicKeyPem();

            byte[] dataToEncrypt = Encoding.UTF8.GetBytes(dataToEncryptString);

            string ciphertextBase64 = Base64Encoding(rsaEncryptionPkcs1(publicKeyLoad, dataToEncrypt));

            Console.WriteLine("ciphertextBase64: " + ciphertextBase64);

​

            // transport the encrypted data to recipient

            // receiving the encrypted data, decryption

            Console.WriteLine("\n* * * decrypt the ciphertext with the RSA private key * * *");

            string ciphertextReceivedBase64 = ciphertextBase64;

            Console.WriteLine("ciphertextReceivedBase64: " + ciphertextReceivedBase64);

            string privateKeyLoad = loadRsaPrivateKeyPem();

            byte[] ciphertextReceived = Base64Decoding(ciphertextReceivedBase64);

            byte[] decryptedtextByte = rsaDecryptionPkcs1(privateKeyLoad, ciphertextReceived);

            Console.WriteLine("decryptedData: " + Encoding.UTF8.GetString(decryptedtextByte, 0, decryptedtextByte.Length));

        }

        catch(ArgumentNullException) {

            Console.WriteLine("The data was not RSA encrypted");

        }

    }

​

    public static byte[] rsaEncryptionPkcs1(string publicKeyPem, byte[] plaintext) {

        RSA rsaAlg = RSA.Create();

        rsaAlg.ImportFromPem(publicKeyPem);

        var encryptedData = rsaAlg.Encrypt(plaintext, RSAEncryptionPadding.Pkcs1);

        return encryptedData;

    }

​

    public static byte[] rsaDecryptionPkcs1(string privateKeyPem, byte[] ciphertext) {

        RSA rsaAlgd = RSA.Create();

        byte[] privateKeyByte = getRsaPrivateKeyEncodedFromPem(privateKeyPem);

        int _out;

        rsaAlgd.ImportPkcs8PrivateKey(privateKeyByte, out _out);

        var decryptedData = rsaAlgd.Decrypt(ciphertext, RSAEncryptionPadding.Pkcs1);

        return decryptedData;

    }

​

    public static byte[] rsaEncryptionOaepSha1(string publicKeyXml, byte[] plaintext) {

        RSACryptoServiceProvider RSAalg = new RSACryptoServiceProvider(2048);

        RSAalg.PersistKeyInCsp = false;

        RSAalg.FromXmlString(publicKeyXml);

        return RSAalg.Encrypt(plaintext, true);

    }

​

    public static byte[] rsaDecryptionOaepSha1(string privateKeyXml, byte[] ciphertext) {

        RSACryptoServiceProvider RSAalg = new RSACryptoServiceProvider(2048);

        RSAalg.PersistKeyInCsp = false;

        RSAalg.FromXmlString(privateKeyXml);

        return RSAalg.Decrypt(ciphertext, true);

    }

​

    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-----";

    }

}