Cryptology ePrint Archive: Report 2005/226

Security Proof of Sakai-Kasahara's Identity-Based Encryption Scheme

Liqun Chen and Zhaohui Cheng

Abstract: Identity-based encryption (IBE) is a special asymmetric encryption method where a public encryption key can be an arbitrary identifier and the corresponding private decryption key is created by binding the identifier with a system's master secret. In 2003 Sakai and Kasahara proposed a new IBE scheme, which has the potential to improve performance. However, to our best knowledge, the security of their scheme has not been properly investigated. This work is intended to build confidence in the security of the Sakai-Kasahara IBE scheme. In this paper, we first present an efficient IBE scheme that employs a simple version of the Sakai-Kasahara scheme and the Fujisaki-Okamoto transformation, which we refer to as SK-IBE. We then prove that SK-IBE has chosen ciphertext security in the random oracle model based on a reasonably well-explored hardness assumption.

Category / Keywords: public-key cryptography / Identity-based encryption, provable security, bilinear pairings

Date: received 12 Jul 2005, last revised 31 Aug 2005

Contact author: liqun chen at hp com

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Version: 20050831:190627 (All versions of this report)

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