BibTeX
@INPROCEEDINGS{Jakobsson98apractical,
author = {Markus Jakobsson},
title = {A practical mix},
booktitle = {},
year = {1998},
pages = {448--461},
publisher = {Springer-Verlag}
}
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Abstract
vvu.bel1-labs.com/user/markusj Abstract. We introduce a robust and efficient mix-network for expo-nentiation, and use it to obtain a threshold decryption mix-network 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 trans-parent 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 Diffie-Hellman assumption, holds. Of possible independent interest are two new methods that we intro-duce: blinded destructive robustness, a type of destructive robustness with protection against leaks of secret information; and repetition ro-bustness, 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 un-blinded, 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 El-Gamal encryption scheme, making the resulting scheme non-malleable in the random oracle model. This is done by interpreting part of the ci-phertext as a public key, and sign the ciphertext using the corresponding secret key.
