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In type systems with dependency tracking, programmers can assign an ordered set of levels to computations and prevent information flow from high-level computations to the low-level ones. The key notion in such systems isindistinguishability: a definition of program equivalence that takes into account the parts of the program that an observer may depend on. In this paper, we investigate the use of dependency tracking in the context of dependently-typed languages. We present the Dependent Calculus of Indistinguishability (DCOI), a system that adopts indistinguishability as the definition of equality used by the type checker. DCOI also internalizes that relation as an observer-indexed propositional equality type, so that programmers may reason about indistinguishability within the language. Our design generalizes and extends prior systems that combine dependency tracking with dependent types and is the first to support conversion and propositional equality at arbitrary observer levels. We have proven type soundness and noninterference theorems for DCOI and have developed a prototype implementation of its type checker.
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Dual-Mode NIZKs: Possibility and Impossibility Results for Property Transfer.
This paper formulates, and studies, the problem of property transference in dual-mode NIZKs. We say that a property P (such as soundness, ZK or WI) transfers, if, one of the modes having P allows us to prove that the other mode has the computational analogue of P, as a consequence of nothing but the indistinguishability of the CRSs in the two modes. Our most interesting finding is negative; we show by counter-example that the form of soundness that seems most important for applications fails to transfer. On the positive side, we develop a general framework that allows us to show that zero knowledge, witness indistinguishability, extractability and weaker forms of soundness do transfer. Our treatment covers conventional, designated-verifier and designated-prover NIZKs in a unified way.
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- Award ID(s):
- 1717640
- PAR ID:
- 10298319
- Editor(s):
- Bhargavan, Karthikeyan; Oswald, Elisabeth; Prabhakaran, Manoj
- Date Published:
- Journal Name:
- Progress in Cryptology - INDOCRYPT 2020 - 21st International Conference on Cryptology in India, Proceedings. Lecture Notes in Computer Science, Springer
- Volume:
- 12578
- Page Range / eLocation ID:
- 859-881
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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