Time Specific Encryption with Constant Size Secret Keys Secure under Standard Assumption
In Time Specific Encryption (TSE) [Paterson&Quaglia, SCN'10] system, each secret key (resp. ciphertext) is associated with a time period t [0,T 1] (resp. a time interval [L,R] where L,R [0,T 1] A ciphertext under [L,R] is correctly decrypted by any secret key for any time t included in the interval, i.e. t [L,R] TSE's generic construction from identity based encryption (IBE) (resp. hierarchical IBE (HIBE) from which we obtain a concrete TSE scheme with secret keys of size O(log T |g| (resp. O(log T |g| and ciphertexts of size O(log T |g| (resp. O(1)|g| has been proposed in [Paterson&Quaglia, SCN'10] (resp. [Kasamatsu et al. SCN'12] where |g| denotes bit length of an element in a bilinear groupG. In this paper, we propose another TSE's generic construction from wildcarded identity based encryption (WIBE) Differently from the original WIBE [Abdalla et al. ICALP'06] we consider WIBE w/o (hierarchical) key delegatability. By instantiating the TSE's generic construction, we obtain the first concrete scheme with constant size secret keys secure under a standard (static) assumption. Specifically, it has secret keys of size O(1)|g| and ciphertexts of size O(log T |g| and achieves security under the decisional bilinear Diffie Hellman (DBDH) assumption.
IACR Cryptol. ePrint Arch.