Question

I have the following code below to generate an OpenSSL RSA public and private key using OpenSSL.Net. However, I can’t seem to find a way to decrypt data with a given private key. I know if I call generate keys and then the corresponding methods to encrypt and decrypt the data it works fine. However, if I am trying to decrypt something from an external source given a public key, how can I decrypt using that key.

Note: Please do not give examples that don’t use OpenSSL.NET. The Microsoft Cryptographic providers are far slower than OpenSSL and do not meet my speed requirements.

Thanks!

public class AsymmetricKeyResult
{
    public string PublicKey { get; set; }
    public string PrivateKey { get; set; }

    public AsymmetricKeyResult(string publicKey, string privateKey)
    {
        this.PublicKey = publicKey;
        this.PrivateKey = privateKey;
    }
}

public static AsymmetricKeyResult GenerateAsymmetricKeys(int keyLength)
{
    RSA rsa = new RSA();
    rsa.GenerateKeys(keyLength, 0x10021, null, null);
    AsymmetricKeyResult kResult = new AsymmetricKeyResult(rsa.PublicKeyAsPEM, rsa.PrivateKeyAsPEM);

    return kResult;
}

Answer 1

I ended up figuring it out through the object browser on the Managed Wrapper for OpenSSL.NET. This works:

    public static byte[] AsymmetricEncrypt(string publicKeyAsPem, byte[] payload)
    {
        CryptoKey d = CryptoKey.FromPublicKey(publicKeyAsPem, null);
        RSA rsa = d.GetRSA();
        byte[] result = rsa.PublicEncrypt(payload, RSA.Padding.PKCS1);
        rsa.Dispose();
        return result;
    }

    public static byte[] AsymmetricDecrypt(string privateKeyAsPem, byte[] payload)
    {
        CryptoKey d = CryptoKey.FromPrivateKey(privateKeyAsPem, null);
        RSA rsa = d.GetRSA();
        byte[] result = rsa.PrivateDecrypt(payload, RSA.Padding.PKCS1);
        rsa.Dispose();
        return result;
    }