Chosen‐Ciphertext Security from Identity‐Based Encryption

TLDR

The authors propose simple and efficient CCA‑secure public‑key encryption schemes based on any identity‑based encryption scheme. These schemes are built by leveraging any existing IBE scheme to achieve adaptive chosen‑ciphertext security. The constructions introduce a new paradigm that bypasses proofs of well‑formedness, achieve competitive performance when instantiated with known IBE schemes, and enable the first efficient CCA‑secure IBE schemes, including hierarchical ones.

Abstract

We propose simple and efficient CCA‐secure public‐key encryption schemes (i.e., schemes secure against adaptive chosen‐ciphertext attacks) based on any identity‐based encryption (IBE) scheme. Our constructions have ramifications of both theoretical and practical interest. First, our schemes give a new paradigm for achieving CCA‐security; this paradigm avoids “proofs of well‐formedness” that have been shown to underlie previous constructions. Second, instantiating our construction using known IBE constructions we obtain CCA‐secure encryption schemes whose performance is competitive with the most efficient CCA‐secure schemes to date. Our techniques extend naturally to give an efficient method for securing IBE schemes (even hierarchical ones) against adaptive chosen‐ciphertext attacks. Coupled with previous work, this gives the first efficient constructions of CCA‐secure IBE schemes.