CP-ABE Scheme with Decryption Keys of Constant Size Using ECC with Expressive Threshold Access Structure

With the rapid development of cross-organizational application systems that are geographically distributed, the notion of Virtual Organization (VO) is indispensable. The inevitable existence of global information infrastructure in every field has forced virtual organizations to gain importance as a fitting model for making a large-scale organization of distributed nature. Virtual organization mainly deals with the devolution of responsibilities to other organizations and providing goods and services by having mutual cooperation among organizations. An ancient mechanism is essential to have controlled access to shared resources and proper participation policies. However, this controlled access is challenging in the case of VO because of its distributed nature. Thus, a mechanism which can handle complex access policies is needed. The mechanism is also required to be reasonably scalable and efficient. In this paper, we propose a threshold access structure implemented using Elliptic Curve Cryptography, which is much better in terms of efficiency. Our main contribution is that we propose a threshold access structure that uses ECC and provides constant-size secret keys for the Ciphertext Policy Attribute-based Encryption (CP-ABE) scheme. In essence, we suggest a formal procedure to share secret information using encryption, where secret messages are associated with a policy, and only the users who have this specific attribute set that fulfils the specified policy will be apt to successfully decrypt and gain access to the secret message/information.