A Generic Construction of Timed-Release Encryption with Pre-open Capability

  • Authors:
  • Yasumasa Nakai;Takahiro Matsuda;Wataru Kitada;Kanta Matsuura

  • Affiliations:
  • The University of Tokyo, Tokyo, Japan;The University of Tokyo, Tokyo, Japan;The University of Tokyo, Tokyo, Japan;The University of Tokyo, Tokyo, Japan

  • Venue:
  • IWSEC '09 Proceedings of the 4th International Workshop on Security: Advances in Information and Computer Security
  • Year:
  • 2009

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Abstract

In 2005, Hwang et al. proposed a concept of timed-release encryption with pre-open capability (TRE-PC), where a receiver can decrypt a ciphertext not only by using a time-release key which is provided after its release-time, but also using a secret information called a pre-open key provided from a sender even before the release-time. Though there are several concrete constructions of TRE-PC proposed so far, no generic construction has been known. In this paper, we show a generic construciton of TRE-PC. Specifically, we construct a TRE-PC scheme from a chosen-ciphertext secure public key encryption scheme (PKE), a chosen plaintext secure identity-based encryption (IBE) scheme with specific property that we call target collision resistance for randomness , and a one-time signature scheme. Interestingly, our proposed construction of TRE-PC is essentially the same as the generic construciton of (normal) TRE based on multiple encryption of IBE and PKE. As one of the consequences of our result, we can build a TRE-PC scheme secure in the standard model based on weaker assumptions than the ones used by the existing standard model TRE-PC scheme.