JoWUA

Abstract

Wildcard identity-based encryption (WIBE) is essentially a generalization of Hierarchical identity based encryption (HIBE) where at the time of encryption, the sender can decide to make the ciphertext decryptable by a whole range of users whose identities match a certain pattern, defined as a sequence of identities and wildcards. Almost existing WIBE schemes have a weakness, that is the large ciphertext size. Only very recently, at ESORICS’18, Kim et al. proposed the first WIBE scheme with constant size ciphertext (including four elements), however, the user’s secret key size in their scheme is still large. In this paper, we propose a new WIBE scheme which is an improvement of Kim et al.’s scheme in term of all the ciphertext size, the secret key size and the decryption time. More precisely, in our scheme the ciphertext just contains three elements and user needs to keep only one element secret, all other elements in the user’s secret key can be made public. For decrypting, user in our scheme only needs to compute two Pairings.