Cryptology ePrint Archive: Report 2005/137

A Sender Verifiable Mix-Net and a New Proof of a Shuffle

Douglas Wikström

Abstract: We introduce the first El Gamal based mix-net in which each mix-server partially decrypts and permutes its input, i.e., no re-encryption is necessary. An interesting property of the construction is that a sender can verify non-interactively that its message is processed correctly. We call this sender verifiability.

We prove the security of the mix-net in the UC-framework against static adversaries corrupting any minority of the mix-servers. The result holds under the decision Diffie-Hellman assumption, and assuming an ideal bulletin board and an ideal zero-knowledge proof of knowledge of a correct shuffle.

Then we construct the first proof of a decryption-permutation shuffle, and show how this can be transformed into a zero-knowledge proof of knowledge in the UC-framework. The protocol is sound under the strong RSA-assumption and the discrete logarithm assumption.

Our proof of a shuffle is not a variation of existing methods. It is based on a novel idea of independent interest, and we argue that it is at least as efficient as previous constructions.

Category / Keywords: cryptographic protocols, mix-net, anonymous channel, shuffle, electronic election

Date: received 10 May 2005, last revised 19 Mar 2009

Contact author: dog at nada kth se

Available formats: Postscript (PS) | Compressed Postscript (PS.GZ) | BibTeX Citation

Note: Corrected error in proof of soundness/proof of knowledge.

Version: 20090319:143124 (All versions of this report)

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