2 research outputs found
Dynamic tags for security protocol
The design and verification of cryptographic protocols is a notoriously
difficult task, even in symbolic models which take an abstract view of
cryptography. This is mainly due to the fact that protocols may interact with
an arbitrary attacker which yields a verification problem that has several
sources of unboundedness (size of messages, number of sessions, etc. In this
paper, we characterize a class of protocols for which deciding security for an
unbounded number of sessions is decidable. More precisely, we present a simple
transformation which maps a protocol that is secure for a bounded number of
protocol sessions (a decidable problem) to a protocol that is secure for an
unbounded number of sessions. The precise number of sessions that need to be
considered is a function of the security property and we show that for several
classical security properties a single session is sufficient. Therefore, in
many cases our results yields a design strategy for security protocols: (i)
design a protocol intended to be secure for a {single session}; and (ii) apply
our transformation to obtain a protocol which is secure for an unbounded number
of sessions.Comment: 50 pages with 30 reference
How to Guarantee Secrecy for Cryptographic Protocols
19 pagesRapport interneIn this paper we propose a general definition of secrecy for cryptographic protocols in the Dolev-Yao model. We give a sufficient condition ensuring secrecy for protocols where rules have encryption depth at most two, that is satisfied by almost all practical protocols. The only allowed primitives in the class of protocols we consider are pairing and encryption with atomic keys. Moreover, we describe an algorithm of practical interest which transforms a cryptographic protocol into a secure one from the point of view of secrecy, without changing its original goal with respect to secrecy of nonces and keys, provided the protocol satisfies some conditions. These conditions are not very restrictive and are satisfied for most practical protocols