Cmsc 858k — Advanced Topics in Cryptography

Cmsc 858k — Advanced Topics in Cryptography

In this lecture, we study the Byzantine Agreement problem, defined as follows: consider a network of n processors, where each pair of processors can communicate (this is the so-called “point-to-point” model). Furthermore, at most t processors within this network may be faulty; a faulty processor may exhibit arbitrary behavior. (We also assume that the behavior of these faulty processors may be ...

Cmsc 858k — Advanced Topics in Cryptography

In a previous lecture, we saw how to construct a three-round zero-knowledge (ZK) proof system for graph 3-colorability with soundness error 1 − 1/ |E| on a common input G = (V,E). The soundness error can be made negligible, while maintaining zero knowledge, by repeating the protocol |E| · ω(log k) times sequentially (where k is the security parameter); unfortunately, this increases the round co...

Cmsc 858k — Advanced Topics in Cryptography Lecture 24

ZK proofs. Zero-knowledge proofs involve a prover P trying to prove a statement to a verifier V without revealing any knowledge beyond the fact that the statement is true. For example, consider the problem of proving membership in an NP language L, (e.g., graph Hamiltonicity, 3-coloring, etc.). A ZK proof protects against a cheating prover, in the sense that if a prover tries to give a proof fo...

Advanced Topics in Cryptography March 4 , 2004 Lecture 12

Proofs in Cryptography∗

We give a brief overview of proofs in cryptography at a beginners level. We briefly cover a general way to look at proofs in cryptography and briefly compare the requirements to traditional reductions in computer science. We then look at two security paradigms, indistinguishability and simulation based security. We also describe the security models for Secret Key and Public Key systems with app...