RSA Encrypting & Descrypting in C# sample

Program.cs

using System;
using System.Security.Cryptography;
using System.Text;

namespace RsaEncryptionSample
{
    class Program
    {
        static void Main(string[] args)
        {

            var cryptoServiceProvider = new RSACryptoServiceProvider(2048); //2048 - Długość klucza
            var privateKey = cryptoServiceProvider.ExportParameters(true); //Generowanie klucza prywatnego
            var publicKey = cryptoServiceProvider.ExportParameters(false); //Generowanie klucza publiczny

            string publicKeyString = GetKeyString(publicKey);
            string privateKeyString = GetKeyString(privateKey);

            Console.WriteLine("KLUCZ PUBLICZNY: ");
            Console.WriteLine(publicKeyString);
            Console.WriteLine("-------------------------------------------");

            Console.WriteLine("KLUCZ PRYWATNY: ");
            Console.WriteLine(privateKeyString);
            Console.WriteLine("-------------------------------------------");

            string textToEncrypt = GenerateTestString(); 
            Console.WriteLine("TEKST DO ZASZYFROWANIA: ");
            Console.WriteLine(textToEncrypt);
            Console.WriteLine("-------------------------------------------");

            string encryptedText = Encrypt(textToEncrypt, publicKeyString); //Szyfrowanie za pomocą klucza publicznego
            Console.WriteLine("ZASZYFROWANY TEXT: ");
            Console.WriteLine(encryptedText);
            Console.WriteLine("-------------------------------------------");

            string decryptedText = Decrypt(encryptedText, privateKeyString); //Odszyfrowywanie za pomocą klucza prywatnego

            Console.WriteLine("ODSZYFROWANY TEXT: ");
            Console.WriteLine(decryptedText);

        }

        public static string GetKeyString(RSAParameters publicKey)
        {

            var stringWriter = new System.IO.StringWriter();
            var xmlSerializer = new System.Xml.Serialization.XmlSerializer(typeof(RSAParameters));
            xmlSerializer.Serialize(stringWriter, publicKey);
            return stringWriter.ToString();
        }

        public static string Encrypt(string textToEncrypt, string publicKeyString)
        {
            var bytesToEncrypt = Encoding.UTF8.GetBytes(textToEncrypt);

            using (var rsa = new RSACryptoServiceProvider(2048))
            {
                try
                {               
                    rsa.FromXmlString(publicKeyString.ToString());
                    var encryptedData = rsa.Encrypt(bytesToEncrypt, true);
                    var base64Encrypted = Convert.ToBase64String(encryptedData);
                    return base64Encrypted;
                }
                finally
                {
                    rsa.PersistKeyInCsp = false;
                }
            }
        }

        public static string Decrypt(string textToDecrypt, string privateKeyString)
        {
            var bytesToDescrypt = Encoding.UTF8.GetBytes(textToDecrypt);

            using (var rsa = new RSACryptoServiceProvider(2048))
            {
                try
                {

                    // server decrypting data with private key                    
                    rsa.FromXmlString(privateKeyString);

                    var resultBytes = Convert.FromBase64String(textToDecrypt);
                    var decryptedBytes = rsa.Decrypt(resultBytes, true);
                    var decryptedData = Encoding.UTF8.GetString(decryptedBytes);
                    return decryptedData.ToString();
                }
                finally
                {
                    rsa.PersistKeyInCsp = false;
                }
            }
        }

        private static string GenerateTestString()
        {
            Guid opportinityId = Guid.NewGuid();
            Guid systemUserId = Guid.NewGuid();
            string currentTime = DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss");

            StringBuilder sb = new StringBuilder();
            sb.AppendFormat("opportunityid={0}", opportinityId.ToString());
            sb.AppendFormat("&systemuserid={0}", systemUserId.ToString());
            sb.AppendFormat("&currenttime={0}", currentTime);

            return sb.ToString(); 
        }
    }
}

How will I encrypt if only the public key was sent and its in string format rather than xml
eg

KJKJHGUJHGBHJHeMA0GCDW<MNDSSD/XUOSSdfgsdgdfgsdfgsdfgsl+6N6OGDSEFSEFEFEEEFFSD9qJ10q4nW
XyK0pnlcyzxrLXXahp7oSS1dH7s8UC1asgwdasdgsdfgz1eNRLY4zN
aZvi18lppsdfgsdf4545sdgfsdgdhdfsgdrg563456/sdfgdls4j/1asdgwgqw5fgdsgSwrgwr4ghwY4my41DuLmcJ8XvRpAW
Kh8g5jsbyaBpzBA5AgMBAAE=

Please share how we can use public key for decryption

Please share how we can use public key for decryption

You don't. Public keys are only for encryption.

hi, i need to implement encryption starting from a public key in this format "-----BEGIN PUBLIC KEY-----xxxxxxxxxx"
how to change the code to set public key in that format?

thanks

@fabrixiodb It seems you need to generate ssl certificate.
You can use OpenSSL toolkit.

hi, i need to implement encryption starting from a public key in this format "-----BEGIN PUBLIC KEY-----xxxxxxxxxx"
how to change the code to set public key in that format?

thanks

There's no need for manual XML serialization. Just use ToXmlString() instead

var privateKey = cryptoServiceProvider.ToXmlString(true);
var publicKey = cryptoServiceProvider.ToXmlString(false);

Please share how we can use public key for decryption

You don't. Public keys are only for encryption.

You can actually, it is called "Signing" instead of encrypting for some weird reason.