Is there a way to import private keys from the Microsoft\Crypto\RSA\MachineKeys folder?

Question

I\'m looking to interact with the private keys folder (essentially to find a private key to try to pair to a public key, given that a public key isn\'t paired with one already )

Answer 1

Below is the small test code snippet. At offset 0x28 there's a container name that can be used to load Key parameters. I couldn't find any documentation regarding private key file format so it might not work in all cases.

public static RSAParameters LoadParametersFromFile(string fileName)
{
    int provType = 1;
    string provName = "Microsoft Enhanced Cryptographic Provider v1.0"

    // Load key container name;
    StringBuilder containerName = new StringBuilder();
    using (var keyFile = File.OpenRead(fileName))
    {
        keyFile.Position = 0x28;
        int c;
        while ((c = keyFile.ReadByte()) != 0 && c !=-1) containerName.Append((char) c);
    }

    CspParameters csp = new CspParameters(provType, provName);
    csp.Flags = CspProviderFlags.UseMachineKeyStore; // set it accordingly
    csp.KeyContainerName = containerName.ToString();
    using (RSACryptoServiceProvider rsaKey = new RSACryptoServiceProvider(csp))
    {
        RSAParameters loadedParams = rsaKey.ExportParameters(false);
        return loadedParams;
    }
}

Test call:

var rsaParams =  LoadParametersFromFile(@"C:\ProgramData\Microsoft\Crypto\RSA\MachineKeys\0034dc1b91df7f7d75df774fa568bc73_ba648dc7-2ead-41db-8cde-e6f84e3fb1cc");

rsaParams.Modulus will contain the public key.