Cryptology ePrint Archive: Report 2006/267

Stateful Public-Key Cryptosystems: How to Encrypt with One 160-bit Exponentiation

Mihir Bellare and Tadayoshi Kohno and Victor Shoup

Abstract: We show how to significantly speed-up the encryption portion of some public-key cryptosystems by the simple expedient of allowing a sender to maintain state that is re-used across different encryptions. In particular we present stateful versions of the DHIES and Kurosawa-Desmedt schemes that each use only one exponentiation to encrypt, as opposed to two and three respectively in the original schemes, yielding the fastest discrete-log based public-key encryption schemes known in the random-oracle and standard models respectively. The schemes are proven to meet an appropriate extension of the standard definition of IND-CCA security that takes into account novel types of attacks possible in the stateful setting.

Category / Keywords: public-key cryptography /

Publication Info: Preliminary version in ACM CCS 2006. This is the full version.

Date: received 12 Aug 2006, last revised 12 Aug 2006

Contact author: mihir at cs ucsd edu

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Version: 20060812:172715 (All versions of this report)

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