using System;

using System.Security.Cryptography;

using System.Text;

public class Program

{

    public static void Main()

    {

        using (var rsaOriginal = RSA.Create())      // Create original keys

        using (var rsaImportedPriv = RSA.Create())  // For the later import of the private key

        using (var rsaImportedPub = RSA.Create())   // For the later import of the public key

        {

            // Export as DER

            var pkcs8Der = rsaOriginal.ExportPkcs8PrivateKey();

            var spkiDer = rsaOriginal.ExportSubjectPublicKeyInfo();

​

            // Convert to PEM (.NET 5+: using PemEncoding)

            var pkcs8Pem = new string(PemEncoding.Write("PRIVATE KEY", pkcs8Der)); // as of .NET 7: ExportPkcs8PrivateKeyPem

            var spkiPem = new string(PemEncoding.Write("PUBLIC KEY", spkiDer));    // as of .NET 7: ExportSubjectPublicKeyInfoPem

            Console.WriteLine(pkcs8Pem);

            Console.WriteLine(spkiPem);

​

            // Import as PEM

            rsaImportedPriv.ImportFromPem(pkcs8Pem);

            rsaImportedPub.ImportFromPem(spkiPem);

​

            // Test the keys

            Console.WriteLine(

                Encoding.UTF8.GetString(

                    rsaImportedPriv.Decrypt(

                        rsaImportedPub.Encrypt(

                            Encoding.UTF8.GetBytes("The quick brown fox jumps over the lazy dog"), 

                            RSAEncryptionPadding.Pkcs1),

                        RSAEncryptionPadding.Pkcs1)));

        }

    }

}