0

I am trying to implement a licensing solution with DSA Algorithms for my application. Now here is what I have done:

  1. Generated a hardware key, taken its hash.
  2. Generated public and private keys. And encrypted my hash function with private key.
  3. I forward this encrypted value back to client along with the public key.
  4. At client's system, I use the DSASignatureDeformatter's VerifySignature function to validate my encrypted key, and my hardware key. If equal I validate the client.

Now my problem is that how to send the public key over the network. I tried to store and forward various DSAParameters values e.g., J, G, P in a file but since the sizes of keys change, that is not viable. Please see if anyone can guide.

Updated: When I try to do this at the client's machine

    DSAParameters KeyInfo;
    using (DSACryptoServiceProvider DSA = new DSACryptoServiceProvider())
    {

        // Import the key information.
        KeyInfo = DSA.ExportParameters(false);
    }

The key size it generates for its various members is different from the public key parameters I have sent it back from server.

BradleyDotNET
  • 60,462
  • 10
  • 96
  • 117
user1343318
  • 2,093
  • 6
  • 32
  • 59
  • Why are variable key sizes a problem? – Iridium Oct 19 '12 at 09:51
  • Iridium, please see the updated question. I have put some code to explain. I will be grateful for any help. – user1343318 Oct 19 '12 at 10:53
  • I think you're going to need to show more code and provide more detail on the issue you're having - how are you performing the serialization, how are you transmitting it, what errors occur when you try to use the deserialised parameters at the client. (It's also worth mentioning that the scheme as described doesn't seem particularly secure). – Iridium Oct 19 '12 at 12:03

1 Answers1

1

Okay. A bit late. But maybe other ones will have the same question.

You should just export your key like this:

string publicKey = DSA.ToXmlString(false);

so you can import it like this:

using (DSACryptoServiceProvider dsa = new DSACryptoServiceProvider())
{
    dsa.FromXmlString(publicKey);
    return dsa.VerifySignature()
}
myst3rium
  • 154
  • 12