Advances in Cryptology — EUROCRYPT'98
Volume 1403 of the series Lecture Notes in Computer Science pp 448461
A practical mix
 Markus JakobssonAffiliated withInformation Sciences Research Center, Bell Labs
Abstract
We introduce a robust and efficient mixnetwork for exponentiation, and use it to obtain a threshold decryption mixnetwork for ElGamal encrypted messages, in which mix servers do not need to trust each other for the correctness of the result. If a subset of mix servers cheat, they will be caught with an overwhelming probability, and the decryption can restart after replacing them, in a fashion that is transparent to the participants providing the input to be decrypted. As long as a quorum is not controlled by an adversary, the privacy of the mix is guaranteed. Our solution is proved to be secure if a commonly used assumption, the Decision DiffieHellman assumption, holds.
Of possible independent interest are two new methods that we introduce: blinded destructive robustness, a type of destructive robustness with protection against leaks of secret information; and repetition robustness, a method for obtaining robustness for some distributed vector computations. Here, two or more calculations of the same equation are performed, where the different computations are made independent by the use of blinding and permutation. The resulting vectors are then unblinded, sorted and compared to each other. This allows us to detect cheating (resulting in inequality of the vectors).
Also of possible independent interest is a modular extension to the ElGamal encryption scheme, making the resulting scheme nonmalleable in the random oracle model. This is done by interpreting part of the ciphertext as a public key, and sign the ciphertext using the corresponding secret key.
Keywords
mixnetwork decryption privacy robustness error detection Title
 A practical mix
 Book Title
 Advances in Cryptology — EUROCRYPT'98
 Book Subtitle
 International Conference on the Theory and Application of Cryptographic Techniques Espoo, Finland, May 31 – June 4, 1998 Proceedings
 Pages
 pp 448461
 Copyright
 1998
 DOI
 10.1007/BFb0054145
 Print ISBN
 9783540645184
 Online ISBN
 9783540697954
 Series Title
 Lecture Notes in Computer Science
 Series Volume
 1403
 Series ISSN
 03029743
 Publisher
 Springer Berlin Heidelberg
 Copyright Holder
 SpringerVerlag
 Additional Links
 Topics
 Keywords

 mixnetwork
 decryption
 privacy
 robustness
 error detection
 Industry Sectors
 eBook Packages
 Editors
 Authors

 Markus Jakobsson ^{(1)}
 Author Affiliations

 1. Information Sciences Research Center, Bell Labs, 07974, Murray Hill, New Jersey
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