International Association for Cryptologic Research

International Association
for Cryptologic Research

IACR News item: 15 September 2015

S\\\'ebastien Canard, Viet Cuong Trinh
ePrint Report ePrint Report
Attribute-based encryption (ABE) is an extension of traditional public key encryption in which the encryption and decryption phases are based on user\'s attributes. More precisely, we focus on cipher-text-policy ABE (CP-ABE) where the secret-key is associated to a set of attributes and the ciphertext is generated with an access policy. It then becomes feasible to decrypt a ciphertext only if one\'s attributes satisfy the used access policy.

In this paper, we give the first private CP-ABE constructions with a constant-size ciphertext, supporting CNF (Conjunctive Normal Form) access policy, with the simple restriction that each attribute can only appear $k_{max}$ times in the access formula. Our two constructions are based on the BGW scheme at Crypto\'05. The first scheme is basic selective secure (in the standard model) while our second one reaches the selective CCA security (in the random oracle model).

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