Tweaking TBE/IBE to PKE Transforms with Chameleon Hash Functions

  • Authors:
  • Rui Zhang

  • Affiliations:
  • Research Center for Information Security (RCIS), National Institute of Advanced Industrial Science and Technology (AIST),

  • Venue:
  • ACNS '07 Proceedings of the 5th international conference on Applied Cryptography and Network Security
  • Year:
  • 2007

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Abstract

We present two transforms to acquire chosen ciphertext security from tag based techniques. The first one requires the separability of underlying primitives. By separability, informally, we mean the encryption algorithm has special structures and can process the identity and the message independently. Compared with generic transforms [8],it significantly reduces the ciphertext size overhead with only marginal computation cost. Compared with [11], the only known technique which directly achieves chosen ciphertext secure public key encryption from separable identity based primitives, it only requires selective-Tag/ID security of underlying primitives. Our second transform is less efficient but performs generically. Both transforms preserve the public verifiability of underlying primitives, and can be extended to hierarchical identity based encryption (HIBE) and threshold settings. As an independent interest, we also investigate the security requirements of chameleon hash functions to build strongly unforgeable one-time signatures.