Chinese Journal of Computers   Full Text
Title	Some General Results on Anonymity in Hybrid Encryption Schemes
Authors	TIAN Yuan LI Ming-Chu CHEN Zhi-Yu
Address	(Software School of Dalian University of Technology, Dalian, Liaoning 116600)
Year	2007
Issue	No.10(1813—1826)
Abstract &   Background	Abstract Anonymity(key-privacy) as well as 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 weak security concepts some general results on anonymity in public-key encryption are proved, which fall in two categories. The first results are two general conjugate relations between anonymity and data-privacy, i.e., relevant anonymity(relevant data-privacy) together with data-privacy(anonymity) imply anonymity(data-privacy); the second are sufficient conditions for chosen-ciphertext anonymity in Fujisaki-Okamoto and Okamoto-Pointcheval(REACT) hybrid constructions respectively, only containing specific relevant anonymity and some naturally weak data-privacy requirements. As examples show, all these conditions are easy-to-check criterion in practice. These general consequences are applied to some specific schemes and, as a result, anonymity of some well-known schemes are re-established but in a simpler way. Furthermore, NESSIE scheme PSEC-/1/2/3’s chosen-ciphertext anonymity is proved as applications of these general results. keywords computational cryptography; anonymity; provable security; hybrid-scheme; key-privacy background Cryptographic scheme’s anonymity(not only limited to public-key encryption scheme) is a very useful utility to high-level cryptographic protocols design, however, this topic is far less investigated by researchers in comparison with data-privacy properties. In this and some following papers hybrid encryption schemes’ anonymity will be systematically investigated. Such research is part of a project supported by NFS about how to implement trusted computation in a totally untrustable environment(stealthy computing). One of the authors’ approaches is to construct IBE/HIBE-like schemes as a general transformation to deform cryptographic data structures, in which anonymity plays a critical role. This is a very interesting, potentially valuable but pretty new field where there is plenty of new ideas and consequences to be explored ahead.