An improved approach in CP-ABE with proxy re-encryption

A cryptographic encryption technique converts plaintext into ciphertext, which is non-recoverable by a malicious user without knowing the secret key. The Ciphertext Policy Attribute Based Encryption (CP-ABE) scheme aims for a multicast feature. Different users can decrypt the message if their secret key attributes match with the policy of attributes defined in the ciphertext. In literature, various approaches exist to enhance the naïve CP-ABE scheme. In 2021, Wang et al. proposed the proxy re-encryption-based CP-ABE scheme and presented that it is efficient as its predecessors. However, the proposed scheme follows the variable-length ciphertext where the ciphertext size depends on the number of attributes. Such variable-length ciphertext increases the required number of operations for the decryption, leading to the computation overhead at the receiver side. This paper proposes an enhanced CP-ABE-CL-PRE (CP-ABE Constant Length with PRE) scheme to provide the constant length ciphertext with proxy re-encryption. Our proposed scheme is secure under the Decisional Bilinear Diffie-Hellman (DBDH) problem.