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Identity-based encryption (IBE) has many appealing applications. However, some traditional IBE schemes may not be secure in the real world due to the side-channel attacks. Leakage-resilient cryptography can capture these attacks by modeling information leakage that adversary can access. In this paper, we apply a hash proof technique in the existing CCA-secure variant of the Gentry's IBE scheme to construct a new leakage-resilient IBE scheme in the bounded-leakage model. The proposed scheme is more computationally efficient than the original Alwen et al.'s leakage-resilient IBE scheme. It enjoys a shorter key (public/secret key) length, and a higher relative key leakage ratio. The new leakage-resilient scheme is proved semantically secure against adaptive chosen ciphertext attack in the standard model under the truncated augmented bilinear Diffie-Hellman exponent (q-TABDHE) assumption.

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The situation for post‐challenge continuous auxiliary input leakage has not been considered in the cryptography schemes for previous literature. We present a semantic‐security model with post‐challenge continuous auxiliary inputs for identity‐based encryption. In this model, the adversary is permitted to obtain some information of the private keys constantly and to query more information after seeing the challenge ciphertext through the side‐channel attacks. Furthermore, we present an identity‐based encryption scheme resilient to leakage under composite order groups. Our scheme is secure against post‐challenge continuous auxiliary input, adaptive chosen‐identity, and adaptive chosen plaintext attacks under three static assumptions in the standard model. Compared with existing identity‐based encryption schemes under security properties and performance, our scheme is practical. Copyright © 2015 John Wiley & Sons, Ltd.

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Certificate-based encryption is a new cryptography primitive, which can be used to construct efficient public key infrastructure. However, side-channel attacks are not considered in certificate-based encryption. In order to capture these attacks, we formalize security model of certificate-based encryption with leakage resilience. Furthermore, we present a leakage-resilient certificate-based encryption (LR-CBE) scheme. To the best of our knowledge, this is the first LR-CBE scheme. Based on decision bilinear Diffie-Hellman assumption and decision generalized bilinear Diffie-Hellman assumption, we prove that our scheme is secure against adaptive chosen ciphertext attacks in the random oracle model. Our scheme includes a certificate-based key encapsulation algorithm and a symmetric encryption algorithm, where the encapsulated information is a symmetric key that is used to encrypt message. In order to obtain leakage-resilient property, two-source extractor is used to randomize the symmetric key. The designed scheme can resist entropy leakage. The performance analysis of leakage resilience shows that the relative leakage ratio almost amounts to 1.