Cryptology ePrint Archive: Report 2007/130

Some Results on Anonymity in Hybrid Encryption

Tian Yuan and Chen Zhi-Yu and Jin Yuee and Jin Feng and Ma Huihui

Abstract: Anonymity(key-privacy) as well as security(data-privacy) are all important features in public-key encryption applications. In this paper two new and general concepts, named “relevant anonymity” and “relevant security”, are defined. Based-upon these concepts some general results on anonymity in public-key encryption are proved, which fall in three categories. The first results are two general relationships between anonymity and security; the second are a sufficient and necessary condition for chosen-plaintext anonymity in Fujisaki-Okamoto hybrid construction and a sufficient condition for its chosen-ciphertext anonymity; the third is a sufficient condition for chosen-ciphertext anonymity in Okamoto-Pointcheval hybrid construction (REACT). All these conditions are also easy-to-use criteria in practice. By examples such general consequences are applied to some specific schemes and as a result anonymity of some well-known schemes are re-established in a simpler way. Furthermore, NISSIE scheme PSEC-/1/2/3’s chosen-ciphertext anonymity are proved.

Category / Keywords: public-key cryptography / Anonymity; Provable Security; Hybrid-Scheme; Key-Privacy

Date: received 10 Apr 2007

Contact author: tianyuan_ca at sina com

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Version: 20070418:121927 (All versions of this report)

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