Hanane Houmani

Jaouhar Fattahi, Mohamed Mejri, Hanane Houmani

In this paper, we look at the property of secrecy through the growth of the protocol. Intuitively, an increasing protocol preserves the secret. For that, we need functions to estimate the security of messages. Here, we give relaxed conditions on the functions and on the protocol and we prove that an increasing protocol is correct when analyzed with functions that meet these conditions.

Jaouhar Fattahi, Mohamed Mejri, Hanane Houmani

In this paper, we present a new semi-decidable procedure to analyze cryptographic protocols for secrecy based on a new class of functions that we call: the Witness-Functions. A Witness-Function is a reliable function that guarantees the secrecy in any protocol proved increasing once analyzed by it. Hence, the problem of correctness becomes a problem of protocol growth. A Witness-Function operates on derivative messages in a role-based specification and introduces new derivation techniques. We give here the technical aspects of the Witness-Functions and we show how to use them in a semi-decidable procedure. Then, we analyze a variation of the Needham-Schroeder protocol and we show that a Witness-Function can also help to teach about flaws. Finally, we analyze the NSL protocol and we prove that it is correct with respect to secrecy.