Cryptology ePrint Archive: Report 2002/025

Making Mix Nets Robust For Electronic Voting By Randomized Partial Checking

Markus Jakobsson and Ari Juels and Ron Rivest

Abstract: We propose a new technique for making mix nets robust, called randomized partial checking (RPC). The basic idea is that rather than providing a proof of completely correct operation, each server provides strong evidence of its correct operation by revealing a pseudo-randomly selected subset of its input/output relations.

Randomized partial checking is exceptionally efficient compared to previous proposals for providing robustness; the evidence provided at each layer is shorter than the output of that layer, and producing the evidence is easier than doing the mixing. It works with mix nets based on any encryption scheme (i.e., on public-key alone, and on hybrid schemes using public-key/symmetric-key combinations). It also works both with Chaumian mix nets where the messages are successively encrypted with each servers' key, and with mix nets based on a single public key with randomized re-encryption at each layer.

Randomized partial checking is particularly well suited for voting systems, as it ensures voter privacy and provides assurance of correct operation. Voter privacy is ensured (either probabilistically or cryptographically) with appropriate design and parameter selection. Unlike previous work, our work provides voter privacy as a global property of the mix net rather than as a property ensured by a single honest server. RPC-based mix nets also provide very high assurance of a correct election result, since a corrupt server is very likely to be caught if it attempts to tamper with even a couple of ballots.

Category / Keywords: applications / mix network, mix net, shuffle network, electronic voting, randomized partial checking, public verifiability

Date: received 26 Feb 2002

Contact author: mjakobsson at rsasecurity com

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Version: 20020226:175950 (All versions of this report)

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