SSL: how to use Multiple Private key/Certificate pair for authentication.

Question

Hi all,
i am implementing SSL in java using X509 Certificate/private key combination.
i have two set of private key/certificate pair.
one is factory default and another is generated at run time.
my problem is to try ssl connection with both pairs on same tcp/ip connection.
e.g. on server side: first try ssl connection with factory default certificate, if it fails try connecting with generated certificate on same tcp/ip connection.
on client side: if generated certificate(this certificate was generated at server side) is present first perform server authentication using this certificate otherwise authenticate server with factory default certificate.
can someone please help and let me know how do i need to configure both ends(client and server) for achieving the same.
Thanks In Advance
Saurabh Ahuja

Answer 1

Client code does not contain any default truststore and needs a certificate for authentication.Of course it does. OpenSSL has a way of doing that: some kind of equivalent for the truststore. None of the stuff you've posted here about generating certificates at runtime has any bearing on that problem.
It's like this. The idea of PKI with SSL is as follows:
- the server has a private key and a signed certificate. Preferably it's signed by a CA that the client already trusts, otherwise if it's self-signed it has to be exported from the server's keystore and imported into the truststores of all the clients.
- the client has a truststore that trusts the server, one way or the other, see above.
- the server's private key is private to it. Nobody else has it. Nobody else can ever get it. If it ever leaks, the server is compromised, and server authentication via that private key now means absolutely nothing. You have lost security.
- the server sends its cert to the client along with a digital signature signed by its private key.
- the client (a) decides whether it trusts the cert, via its truststore, and (b) verifies the digital signature, which establishes that the server owns the certificate.
At this point the server is authenticated to the client and the SSL connection is open. It can now be used as an ordinary socket connection.
If you want client authentication too, you need all the above in reverse as well, i.e. reading server for client and client for server throughout. Note particularly that each client must have its own private key. Otherwise the private key isn't private, so signing something with it doesn't establish ownership, so client authentication isn't valid.
You need to understand all this stuff and relate it to the apparently broken security design of your application. Generating a private key and a certificate at runtime is complete nonsense within the context of PKI and SSL. It proves nothing, establishes nothing, authenticates nothing; it just wastes time.