We consider zero knowledge interactive proofs in a richer, more realistic communication environment. In this setting, one may simultaneously engage in many interactive proofs, and these proofs may take place in an asynchronous fashion. It is known that zero-knowledge is not necessarily preserved in such an environment; we show that for a large class of protocols, it cannot be preserved. Any 4 r...

We provide new characterizations of two previously studied questions on nondeterministic function classes: Q1: Do nondeterministic functions admit efficient deterministic refinements? Q2: Do nondeterministic function classes contain complete functions? We show that Q1 for the class NPMVt is equivalent to the question whether the standard proof system for SAT is p-optimal, and to the assumption ...

We discuss the formal approach to Tarski geometry axioms modelled with the help of the Mizar computerized proof assistant system. We try however to go much further from the use of simple predicates in the direction of the use of structures with their inheritance, attributes as a tool of more human-friendly namespaces for axioms, and registrations of clusters to obtain more automation (with the ...

Building on existing work in proxying interaction with proof assistants, we have previously developed a proof movie. We have now considered the problem of how to augment this movie data structure to support commentary on formal proof development. In this setting, we have studied extracting commentary from an online text by Pierce et al. [11].

Undeniable signature schemes are not publicly verifiable. Therefore, in order to prove the validity/invalidity of a message-signature pair, the signer needs to provide a proof for the rightful verifier. Since the introduction of undeniable signature schemes, various proof systems with different properties and features have been introduced to be incorporated in the structure of such schemes. Amo...

Recent work on the enhancement of typing techniques for multiparty sessions with logical annotations enables, not only the validation of structural properties of the conversations and on the sorts of the messages, but also properties on the actual values exchanged. However, specification and verification of mutual effects of multiple cross-session interactions are still an open problem. We intr...

This paper describes an embedding of higher-order modal logics in the Coq proof assistant. Coq’s capabilities are used to implement modal logics in a minimalistic manner, which is nevertheless su cient for the formalization of significant, non-trivial modal logic proofs. The elegance, flexibility and convenience of this approach, from a user perspective, are illustrated here with the successful...

Since their introduction in 2008, the non-interactive zeroknowledge (NIZK) and non-interactive witness indistinguishable (NIWI) proofs designed by Groth and Sahai have been used in numerous applications. In this paper, we offer two contributions to the study of these proof systems. First, we identify and correct some errors, present in the oringal online manuscript, that occur in two of the thr...

We study cryptocurrency protocols that do not make use of Proof of Work. Such protocols commonly rely on Proof of Stake, i.e. on mechanisms that extend voting power to the stakeholders of the system. We offer analysis of existing protocols that have a substantial amount of popularity. We then present our novel pure Proof of Stake protocols, and argue that the they help in mitigating problems th...

This is a description of a plan for new research which has been awarded an Eclipse Innovation Grant for 2004. The objective is to build a proof development environment for interactive theorem provers, using ideas of the Proof General project, and in particular, using a protocol for interactive proof dubbed PGIP.