International Association for Cryptologic Research

International Association
for Cryptologic Research


Paper: Analysis and Improvement of Authenticatable Ring Signcryption Scheme

Fagen Li
Masaaki Shirase
Tsuyoshi Takagi
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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.
  title={Analysis and Improvement of Authenticatable Ring Signcryption Scheme},
  booktitle={IACR Eprint archive},
  keywords={public-key cryptography / Identity-based cryptography, bilinear pairings, ring signcryption, ring signature},
  note={Full version of a paper that will be published (short paper track) in the 2nd International Conference on Provable Security (ProvSec 2008). 14122 received 31 Aug 2008},
  author={Fagen Li and Masaaki Shirase and Tsuyoshi Takagi},