Helger Lipmaa's publications

Verifiable Homomorphic Oblivious Transfer and Private Equality Test

Helger Lipmaa. Verifiable Homomorphic Oblivious Transfer and Private Equality Test. In Chi Sung Laih, editor, Advances on Cryptology --- ASIACRYPT 2003, volume 2894 of Lecture Notes in Computer Science, pages 416--433, Taipei, Taiwan, November 30--December 4, 2003. Springer, Heidelberg.

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Abstract:

We describe slightly modified version (that we call the HOT protocol) of the Aiello-Ishai-Reingold oblivious transfer protocol from Eurocrypt 2001. In particular, the HOT protocol will be what we call weakly secure when coupled with many different homomorphic semantically secure public-key cryptosystems. Based on the HOT protocol, we construct an efficient verifiable oblivious transfer protocol and an efficient verifiable private equality test. As a concrete application of our results, we propose a novel protocol called proxy verifiable private equality test, and apply it to a cryptographic auction scheme to improve its security.

Keywords: Cryptographic auctions, homomorphic encryption, verifiable oblivious transfer, verifiable private equality test.

Slides:


Comment: As pointed out in eprint 2005/378 (published in ACNS 2007), Theorem 2 of this paper is faulty (I was aware of this by summer 2004); the ACNS paper proposes a correct generalization of AIR to composite-order groups. Also, as we pointed out in eprint 2006/088, the verifiable protocols are not actually verifiable, but satisfy a somewhat weaker property that we called consistency. Anyhow, I recommend not to read this paper, the cited eprints are much more interesting.


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