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

Dennis Hofheinz, Jessica Koch, Christoph Striecks
2015 Lecture Notes in Computer Science  
We 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). The security loss of our reduction is O(k) (where k is the security parameter). Our scheme is the first IBE scheme to achieve this strong flavor
more » ... 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. * Dennis Hofheinz was supported by DFG grants GZ HO 4534/2-2 and GZ HO 4534/4-1.
doi:10.1007/978-3-662-46447-2_36 fatcat:7ck25hyksjclpkumbqwpbuvnzi