C# (.NET) RSACryptoServiceProvider import/export x509 public key blob and PKCS8 private key blob

Question

first of all let me state that I'm not a crypto expert but i know the basics.

I want to be able to:

Get a RSACryptoServiceProvider instance from a X509 Public Key blob
Get a RSACryptoServiceProvider instance from a PKCS8 Private Key blob
Export the public key from a RSACryptoServiceProvider instance as a x509 Public Key blob
Export the private key from a RSACryptoServiceProvider instance as a PKCS8 blob

You are encrypting with private key and decrypting with the public one. This is called digital-signature and has specific methods in Java and C#. Really is what you want to do? Usually encryption is performed with public key and decryption with private. — pedrofb
Note also that importing a RSA public key is not trivial.stackoverflow.com/questions/18091460/rsa-read-publickey — pedrofb
@pedrofb i was already onto it. I've got to parse the binary asn.1 X509PKInfo into a RSAParameters object. I'll provide a code solution when once i finish it. — loveMeansNothing

loveMeansNothing loveMeansNothing · Accepted Answer · 2016-11-27T02:19:42

After looking around all day, i've found this repository (thanks a lot jrnker) and i selected the code i needed to able to met the goals 1, 2 and 3.

Since Jrnker's only provides methods to get a RSACryptoServiceProvider from a PKCS1 blob (and what i needed was a RSACryptoServiceProvider from a PKCS8 blob) i kept looking to met goal number 4. Then i've found Michel Gallant's "opensslkey.cs" and i selected the needed code to met goal number 4.

Then i've proceeded to compile a class with needed methods and classes.

Here's my demo class:

using System;

namespace RSAKeyTests
{
    class Demo
    {
        static void Main(string[] args)
        {
            //EXPORTED KEYS
            string importedPublicKeyBase64 = "MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAhbVC4aUR+XRCepBcPlod69wruXqwW9yL/YJYvuaQ33QxUoAehQ0z4SuphHwEPxQp/qLqucmE6XKlEeTksFAmaGM88uuGessqMZmdu9WFhc07MWLTCifR43IRtGEeWeFSWjUI6mNRrShP3QQ3+Z6e7w+HRA2RpmgNgEhJRvECHAKpcpHvP9o5Sq6q/dIAyR6NEjRFhfud27rFtnWrLj+ZmIsScemvks4vh8V3n8EzxxRE8nzVuZYr4v4NNH+q95XgIadHZ1Y6ICXJgX2NfacNRQl9+SEv0Wo8lbmFSIO3jHqyiWuSugv7R3/rQPRXHT6HJAtw0tBiPOBitMkTzqOvIwIDAQAB";
            string importedPrivateKeyBase64 = "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";
            byte[] importedPublicKeyBytes = Convert.FromBase64String(importedPublicKeyBase64);
            byte[] importedPrivateKeyBytes = Convert.FromBase64String(importedPrivateKeyBase64);

            //PRINT INFO
            Console.WriteLine("------   IMPORTED KEY PAIR:   ------\n");
            Console.WriteLine("PUBLIC KEY:\n"+importedPublicKeyBase64+"\n\n");
            Console.WriteLine("PRIVATE KEY:\n" + importedPrivateKeyBase64 + "\n\n");

            //GENERATING RSACRYPTOSERVICEPROVIDER FROM X509 PUBLIC KEY BLOB
            using (var providerFromX509pubKey = RSAKeyUtils.DecodePublicKey(importedPublicKeyBytes))
            {
                providerFromX509pubKey.PersistKeyInCsp = false; //DO NOT STORE IN KEYSTORE

                //EXPORT TO X509 PUBLIC KEY BLOB
                byte[] x509pubKeyBytes = RSAKeyUtils.PublicKeyToX509(providerFromX509pubKey.ExportParameters(false));

                //CONVERT TO BASE64
                string x509pubKeyBase64 = Convert.ToBase64String(x509pubKeyBytes);

                //PRINT INFO
                Console.WriteLine("------   PUBLIC KEY TO EXPORT   ------");
                Console.WriteLine("Public key to export matches imported? "+importedPublicKeyBase64.Equals(x509pubKeyBase64));
                Console.WriteLine(x509pubKeyBase64+"\n\n");
            }

            //GENERATING RSACRYPTOSERVICEPROVIDER FROM PKCS8 PRIVATE KEY BLOB
            using (var providerFromPKCS8privKey = RSAKeyUtils.DecodePrivateKeyInfo(importedPrivateKeyBytes))
            {
                providerFromPKCS8privKey.PersistKeyInCsp = false; //DO NOT STORE IN KEYSTORE

                //EXPORT TO PKCS8 PRIVATE KEY BLOB
                byte[] pkcs8privKeyBytes = RSAKeyUtils.PrivateKeyToPKCS8(providerFromPKCS1privKey.ExportParameters(true));

                //CONVERT TO BASE64
                string pkcs8privKeyBase64 = Convert.ToBase64String(pkcs8privKeyBytes);

                //PRINT INFO
                Console.WriteLine("------   PRIVATE KEY TO EXPORT   ------");
                Console.WriteLine("Private key to export matches imported? " + importedPrivateKeyBase64.Equals(pkcs8privKeyBase64));
                Console.WriteLine(pkcs8privKeyBase64);
            }

                //PREVENTS THE PROGRAM FROM EXITING
                Console.ReadKey();
        }
    }
}

Here's the "RSAKeyUtils" class i've compiled.

I hope this can be useful to someone else.

C# (.NET) RSACryptoServiceProvider import/export x509 public key blob and PKCS8 private key blob

2 Answers