Software Library for Ciphertext/Key-Policy Functional Encryption with Simple Usability

Abstract

In traditional public key encryption schemes, data encrypted by a public key pk can be decrypted only by a secret key sk corresponding to pk, and the relation between pk and sk is static. Therefore, the schemes are unsuitable for control of access to a single data by several users. Meanwhile, functional encryption (FE) is an encryption scheme that provides more sophisticated and flexible relations between pk and sk. Thus, FE enables only one pk to encrypt the data with any conditions for decryption, so it is considered a very useful tool for the access control of data on the cloud server. However, implementing the current FE scheme is a non-trivial task because the deep knowledge of the scheme is required. This is an obstacle factor to deploy the FE scheme in the real-world security systems. In this paper, we propose an implementation of the FE (Ciphertext-Policy FE and Key-Policy FE, which are useful classes of FE) library usable even for people who do not have the deep knowledge of these schemes.