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Identity-Based Encryption with (Almost) Tight Security in the Multi-instance, Multi-ciphertext Setting

Authors:
Dennis Hofheinz
Jessica Koch
Christoph Striecks
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DOI: 10.1007/s00145-024-09496-4
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Abstract: AbstractWe construct an identity-based encryption (IBE) scheme that is tightly secure in a very strong sense. Specifically, we consider a setting with many instances of the scheme and many encryptions per instance. In this setting, we reduce the security of our scheme to a variant of a simple assumption used for a similar purpose by Chen and Wee (CRYPTO 2013, Springer, 2013). The security loss of our reduction is $$\textbf{O} (k)$$ O ( k ) (where $$k $$ k is the security parameter). Our scheme is the first IBE scheme to achieve this strong flavor of tightness under a simple assumption. Technically, our scheme is a variation of the IBE scheme by Chen and Wee. However, in order to “lift” their results to the multi-instance, multi-ciphertext case, we need to develop new ideas. In particular, while we build on (and extend) their high-level proof strategy, we deviate significantly in the low-level proof steps.
BibTeX
@article{jofc-2024-34424,
  title={Identity-Based Encryption with (Almost) Tight Security in the Multi-instance, Multi-ciphertext Setting},
  journal={Journal of Cryptology},
  publisher={Springer},
  volume={37},
  pages={12},
  doi={10.1007/s00145-024-09496-4},
  author={Dennis Hofheinz and Jessica Koch and Christoph Striecks},
  year=2024
}