Cryptology ePrint Archive: Report 2008/373

Analysis and Improvement of Authenticatable Ring Signcryption Scheme

Fagen Li and Masaaki Shirase and Tsuyoshi Takagi

Abstract: Ring signcryption is an anonymous signcryption which allows a user to anonymously signcrypt a message on behalf of a set of users including himself. In an ordinary ring signcryption scheme, even if a user of the ring generates a signcryption, he also cannot prove that the signcryption was produced by himself. In 2008, Zhang, Yang, Zhu, and Zhang solve the problem by introducing an identity-based authenticatable ring signcryption scheme (denoted as the ZYZZ scheme). In the ZYZZ scheme, the actual signcrypter can prove that the ciphertext is generated by himself, and the others cannot authenticate it. However, in this paper, we show that the ZYZZ scheme is not secure against chosen plaintext attacks. Furthermore, we propose an improved scheme that remedies the weakness of the ZYZZ scheme. The improved scheme has shorter ciphertext size than the ZYZZ scheme. We then prove that the improved scheme satisfies confidentiality, unforgeability, anonymity and authenticatability.

Category / Keywords: public-key cryptography / Identity-based cryptography, bilinear pairings, ring signcryption, ring signature

Publication Info: Journal of Shanghai Jiaotong University (Science)

Date: received 31 Aug 2008, last revised 7 Apr 2009

Contact author: fagenli at uestc edu cn

Available format(s): Postscript (PS) | Compressed Postscript (PS.GZ) | PDF | BibTeX Citation

Version: 20090408:054440 (All versions of this report)

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