Helger Lipmaa's publications

On the Feasibility of Consistent Computations

Sven Laur and Helger Lipmaa. On the Feasibility of Consistent Computations. In Phong Q. Nguyen and David Pointcheval, editors, PKC 2010, volume 6056 of Lecture Notes in Computer Science, pages 88--106, Paris, France, May 26--28, 2010. Springer, Heidelberg.

File: [.pdf (207 KB)] pdf recommended.


In many practical settings, participants are willing to deviate from the protocol only if they remain undetected. Aumann and Lindell introduced a concept of covert adversaries to formalize this type of corruption. In the current paper, we refine their model to get stronger security guarantees. Namely, we show how to construct protocols, where malicious participants cannot learn anything beyond their intended output and honest participants can detect malicious behavior that alters their outputs. As this construction does protect honest parties from selective protocol failures, a valid corruption complaint can leak a single bit of information about the inputs of honest parties. Importantly, it is often up to the honest party to decide whether to complain or not. Moreover, in practice, this potential leakage is often outweighed by the efficiency compared to standard zero-knowledge based proofs. As a concrete practical contribution, we show how to implement consistent versions of several important cryptographic protocols such as oblivious transfer, conditional disclosure of secrets and private inference control..

Keywords: Consistency, equivocal and extractable commitment, oblivious transfer, private inference control.


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