Cryptology ePrint Archive: Report 2008/342

Cryptanalysis of Li et al.'s Identity-Based Threshold Signcryption Scheme

S. Sharmila Deva Selvi and S. Sree Vivek and Neha Jain and Pandu Rangan Chandrasekaran

Abstract: Signcryption is a cryptographic primitive that aims at providing confidentiality and authentication simultaneously. Recently in May 2008, a scheme for identity based threshold signcryption was proposed by Fagen Li and Yong Yu. They have proved the confidentiality of their scheme and have also claimed the unforgeability without providing satisfactory proof. In this paper, we show that in their signcryption scheme the secret key of the sender is exposed(total break) to the clerk during sincryption and hence insecure in the presence of malicious clerks. Further, we propose a corrected version of the scheme and formally prove its security under the existing security model for signcryption.

Category / Keywords: public-key cryptography / Cryptanalysis, Threshold Signcryption, Identity-Based, Pairing

Date: received 4 Aug 2008

Contact author: prangan55 at gmail com

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

Note: Submitted to TSP '08

Version: 20080811:070212 (All versions of this report)

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