Design of a new CP-ABE with constant-size secret keys for lightweight devices using elliptic curve cryptography

The energy cost of public-key cryptography is a vital component of modern secure communications. It inhibits the widespread adoption within the ultra-low energy regimes (for example, implantable medical devices and Radio Frequency Identification tags). In the ciphertext-policy attribute-based encryption (CP-ABE), an encryptor can decide the access policy that who can decrypt the data. Thus, data will be protected from the unauthorized users. However, most of the existing CP-ABE schemes require huge storage and computational overheads. Moreover, CP-ABE schemes based on bilinear map loose high efficiency over the elliptic curve cryptography because of the requirement of the security parameters of larger size. These drawbacks prevent the use of ultra-low energy devices in practice. In this paper, we aim to propose a novel expressive AND gate access structured CP-ABE scheme with constant-size secret keys (CSSK) with cost-efficient solutions for encryption and decryption using elliptic curve cryptography, called the CP-ABE-CSSK scheme. In the proposed CP-ABE-CSSK, the size of the secret key is as small as 320 bits. In addition, elliptic curve cryptography is efficient and more suitable for lightweight devices as compared with bilinear pairing-based cryptosystem. Thus, the proposed CP-ABE-CSSK scheme provides low computation and storage overheads with an expressive AND gate access structure as compared with related existing schemes. Consequently, our scheme becomes very practical for CP-ABE key storage and computation cost for ultra-low energy devices. Copyright (C) 2016 John Wiley & Sons, Ltd.