US Patent 7673141 Client authentication using a challenge provider

A system for providing secured access to an application service includes a challenge provider that uses a first cryptographic technique to provide a challenge to a client seeking access to an application service. The client uses a second cryptographic technique to generate a response, and provides the response to an authentication service. The authentication service grants the client access to the application service only if the challenge and response are authenticated using a first authentication technique complementary to the first cryptographic technique and a second authentication technique complementary to the second cryptographic technique, respectively.