International Association for Cryptologic Research

International Association
for Cryptologic Research


Paper: Online/Offline Identity-Based Signcryption Re-visited

Joseph K. Liu
Joonsang Baek
Jianying Zhou
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Abstract: In this paper, we re-define a cryptographic notion called Online/Offline Identity-Based Signcryption. It is an ``online/offline'' version of identity-based signcryption, where most of the computations are carried out offline and the online part does not require any heavy computations such as pairings or multiplications on elliptic curve. It is particularly suitable for power-constrained devices such as smart cards. We give a concrete implementation of online/offline identity-based signcryption. The construction is very efficient and flexible. Unlike all previous schemes in the literature, our scheme does not require the knowledge of receiver's information (either public key or identity) in the offline stage. The receiver's identity and the message to be signcrypted are only needed in the online stage. This feature provides great flexibility to our scheme and makes it practical to use in real-world applications. We prove that the proposed scheme meets strong security requirements in the random oracle model, assuming the Strong Diffie-Hellman (SDH) and Bilinear Diffie-Hellman Inversion (BDHI) are computationally hard.
  title={Online/Offline Identity-Based Signcryption Re-visited},
  booktitle={IACR Eprint archive},
  keywords={public-key cryptography / Online, offline, ID-based, signcryption},
  note={ 14796 received 10 May 2010, last revised 5 Jul 2010},
  author={Joseph K. Liu and Joonsang Baek and Jianying Zhou},