Flaws in Robust Optimistic Mix-Nets and Stronger Security Notions

Masayuki ABE; Hideki IMAI

doi:10.1093/ietfec/e89-a.1.99

Flaws in Robust Optimistic Mix-Nets and Stronger Security Notions

Masayuki ABE, Hideki IMAI

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Contribution of this paper is twofold: First we introduce weaknesses of two Mix-nets claimed to be robust in the literature. Since such flaws are due to their weak security definitions, we then present a stronger security definition by regarding a Mix-net as a batch decryption algorithm of a CCA secure public-key encryption scheme. We show two concrete attacks on the schemes proposed in [1] and [2]. The scheme in [1] loses anonymity in the presence of a malicious user even though all servers are honest. The scheme in [2] also loses anonymity through the collaboration of a malicious user and the first server. In the later case the user can identify the plaintext sent from the targeted user by invoking two mix sessions at the risk of the colluding server receiving an accusation. We also point out that in a certain case, anonymity is violated solely by the user without colluding to any server. Heuristic repairs are provided for both schemes.

Publication: IEICE TRANSACTIONS on Fundamentals Vol.E89-A No.1 pp.99-105

Publication Date: 2006/01/01

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Online ISSN: 1745-1337

DOI: 10.1093/ietfec/e89-a.1.99

Type of Manuscript: Special Section PAPER (Special Section on Cryptography and Information Security)

Category: Protocol

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Masayuki ABE, Hideki IMAI, "Flaws in Robust Optimistic Mix-Nets and Stronger Security Notions" in IEICE TRANSACTIONS on Fundamentals, vol. E89-A, no. 1, pp. 99-105, January 2006, doi: 10.1093/ietfec/e89-a.1.99.
Abstract: Contribution of this paper is twofold: First we introduce weaknesses of two Mix-nets claimed to be robust in the literature. Since such flaws are due to their weak security definitions, we then present a stronger security definition by regarding a Mix-net as a batch decryption algorithm of a CCA secure public-key encryption scheme. We show two concrete attacks on the schemes proposed in [1] and [2]. The scheme in [1] loses anonymity in the presence of a malicious user even though all servers are honest. The scheme in [2] also loses anonymity through the collaboration of a malicious user and the first server. In the later case the user can identify the plaintext sent from the targeted user by invoking two mix sessions at the risk of the colluding server receiving an accusation. We also point out that in a certain case, anonymity is violated solely by the user without colluding to any server. Heuristic repairs are provided for both schemes.
URL: https://globals.ieice.org/en_transactions/fundamentals/10.1093/ietfec/e89-a.1.99/_p

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@ARTICLE{e89-a_1_99,
author={Masayuki ABE, Hideki IMAI, },
journal={IEICE TRANSACTIONS on Fundamentals},
title={Flaws in Robust Optimistic Mix-Nets and Stronger Security Notions},
year={2006},
volume={E89-A},
number={1},
pages={99-105},
abstract={Contribution of this paper is twofold: First we introduce weaknesses of two Mix-nets claimed to be robust in the literature. Since such flaws are due to their weak security definitions, we then present a stronger security definition by regarding a Mix-net as a batch decryption algorithm of a CCA secure public-key encryption scheme. We show two concrete attacks on the schemes proposed in [1] and [2]. The scheme in [1] loses anonymity in the presence of a malicious user even though all servers are honest. The scheme in [2] also loses anonymity through the collaboration of a malicious user and the first server. In the later case the user can identify the plaintext sent from the targeted user by invoking two mix sessions at the risk of the colluding server receiving an accusation. We also point out that in a certain case, anonymity is violated solely by the user without colluding to any server. Heuristic repairs are provided for both schemes.},
keywords={},
doi={10.1093/ietfec/e89-a.1.99},
ISSN={1745-1337},
month={January},}

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TY - JOUR
TI - Flaws in Robust Optimistic Mix-Nets and Stronger Security Notions
T2 - IEICE TRANSACTIONS on Fundamentals
SP - 99
EP - 105
AU - Masayuki ABE
AU - Hideki IMAI
PY - 2006
DO - 10.1093/ietfec/e89-a.1.99
JO - IEICE TRANSACTIONS on Fundamentals
SN - 1745-1337
VL - E89-A
IS - 1
JA - IEICE TRANSACTIONS on Fundamentals
Y1 - January 2006
AB - Contribution of this paper is twofold: First we introduce weaknesses of two Mix-nets claimed to be robust in the literature. Since such flaws are due to their weak security definitions, we then present a stronger security definition by regarding a Mix-net as a batch decryption algorithm of a CCA secure public-key encryption scheme. We show two concrete attacks on the schemes proposed in [1] and [2]. The scheme in [1] loses anonymity in the presence of a malicious user even though all servers are honest. The scheme in [2] also loses anonymity through the collaboration of a malicious user and the first server. In the later case the user can identify the plaintext sent from the targeted user by invoking two mix sessions at the risk of the colluding server receiving an accusation. We also point out that in a certain case, anonymity is violated solely by the user without colluding to any server. Heuristic repairs are provided for both schemes.
ER -