# Sender-equivocable encryption schemes secure against chosen-ciphertext attacks revisited

Zhengan Huang; Shengli Liu; Baodong Qin; Kefei Chen

International Journal of Applied Mathematics and Computer Science (2015)

- Volume: 25, Issue: 2, page 415-430
- ISSN: 1641-876X

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topZhengan Huang, et al. "Sender-equivocable encryption schemes secure against chosen-ciphertext attacks revisited." International Journal of Applied Mathematics and Computer Science 25.2 (2015): 415-430. <http://eudml.org/doc/270433>.

@article{ZhenganHuang2015,

abstract = {Fehr et al. (2010) proposed the first sender-equivocable encryption scheme secure against chosen-ciphertext attacks (NCCCA) and proved that NC-CCA security implies security against selective opening chosen-ciphertext attacks (SO-CCA). The NC-CCA security proof of the scheme relies on security against substitution attacks of a new primitive, the “crossauthentication code”. However, the security of the cross-authentication code cannot be guaranteed when all the keys used in the code are exposed. Our key observation is that, in the NC-CCA security game, the randomness used in the generation of the challenge ciphertext is exposed to the adversary. Based on this observation, we provide a security analysis of Fehr et al.'s scheme, showing that its NC-CCA security proof is flawed. We also point out that the scheme of Fehr et al. encrypting a single-bit plaintext can be refined to achieve NC-CCA security, free of the cross-authentication code. Furthermore, we propose the notion of “strong cross-authentication code”, apply it to Fehr et al.'s scheme, and show that the new version of the latter achieves NC-CCA security for multi-bit plaintexts.},

author = {Zhengan Huang, Shengli Liu, Baodong Qin, Kefei Chen},

journal = {International Journal of Applied Mathematics and Computer Science},

keywords = {sender-equivocable encryption; chosen-ciphertext attack; cross-authentication code},

language = {eng},

number = {2},

pages = {415-430},

title = {Sender-equivocable encryption schemes secure against chosen-ciphertext attacks revisited},

url = {http://eudml.org/doc/270433},

volume = {25},

year = {2015},

}

TY - JOUR

AU - Zhengan Huang

AU - Shengli Liu

AU - Baodong Qin

AU - Kefei Chen

TI - Sender-equivocable encryption schemes secure against chosen-ciphertext attacks revisited

JO - International Journal of Applied Mathematics and Computer Science

PY - 2015

VL - 25

IS - 2

SP - 415

EP - 430

AB - Fehr et al. (2010) proposed the first sender-equivocable encryption scheme secure against chosen-ciphertext attacks (NCCCA) and proved that NC-CCA security implies security against selective opening chosen-ciphertext attacks (SO-CCA). The NC-CCA security proof of the scheme relies on security against substitution attacks of a new primitive, the “crossauthentication code”. However, the security of the cross-authentication code cannot be guaranteed when all the keys used in the code are exposed. Our key observation is that, in the NC-CCA security game, the randomness used in the generation of the challenge ciphertext is exposed to the adversary. Based on this observation, we provide a security analysis of Fehr et al.'s scheme, showing that its NC-CCA security proof is flawed. We also point out that the scheme of Fehr et al. encrypting a single-bit plaintext can be refined to achieve NC-CCA security, free of the cross-authentication code. Furthermore, we propose the notion of “strong cross-authentication code”, apply it to Fehr et al.'s scheme, and show that the new version of the latter achieves NC-CCA security for multi-bit plaintexts.

LA - eng

KW - sender-equivocable encryption; chosen-ciphertext attack; cross-authentication code

UR - http://eudml.org/doc/270433

ER -

## References

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