English

Abstract

Attribute-based encryption (ABE) is a public-key based one-to-many encryption that allows users to encrypt and decrypt data based on user attributes. A promising application of ABE is flexible access control of encrypted data stored in the cloud, using access polices and ascribed attributes associated with private keys and Ciphertexts. One of the main efficiency drawbacks of the existing ABE schemes is that decryption involves expensive pairing operations and the number of such operations grows with the complexity of the access policy. In ABE system, a user provides an untrusted server, say a cloud service provider, with a transformation key that allows the cloud to translate any ABE ciphertext satisfied by that user's attributes or access policy into a simple ciphertext, and it only incurs a small computational overhead for the user to recover the plaintext from the transformed ciphertext. However, it does not guarantee the correctness of the transformation done by the cloud. In the existing system, a new requirement of ABE with outsourced decryption: verifiability. Informally, verifiability guarantees that a user can efficiently check if the transformation is done correctly. In the proposed Categorical Heuristics on Attribute-based Encryption (CHAE) is an adaptation of Attribute Based Encryption (ABE) for the purposes of providing guarantees towards the provenance of the signed data, and moreover towards the anonymity of the signer. Finally, show an implementation of our scheme and result of performance measurements, which indicates a significant reduction on computing resources imposed on users.