Secure Authentication from a Weak Key, Without Leaking Information

We study the problem of authentication based on a weak key in the information-theoretic setting. A key is weak if its min-entropy is an arbitrary small fraction of its bit length. This problem has recently received considerable attention, with different solutions optimizing different parameters. We study the problem in an extended setting, where the weak key is as a one-time session key that is derived from a public source of randomness with the help of a (potentially also weak) long-term key. Our goal now is to authenticate a message by means of the weak session key in such a way that (nearly) no information on the long-term key is leaked. Ensuring privacy of the long-term key is vital for the long-term key to be re-usable. Previous work has not considered such a privacy issue, and previous solutions do not seem to satisfy this requirement. We show the existence of a practical four-round protocol that provides message authentication from a weak session key and that avoids non-neglig...

• Type: Journal
• Year: 2011
• Where: IACR
• Authors: Niek J. Bouman, Serge Fehr
• Keywords: IACR 2011, Message Authentication, Session Key, Storage Model