The presence of multiple authorities in multi-authority ciphertext policy attribute based encryption (CPABE) schemes hinders an adversary's ability to compromise security. As each authority is responsible to provide secret keys to the users, thus enforcement of finegrained access control should be carefully designed to ensure data confidentiality. The current study critically reviews the methodologies employed to address user-level and attribute-level revocation in the existing studies. The study has focused on the revocation methodology of those CPABE schemes that are implemented using bilinear pairing cryptography for the encryption and Linear Secret Sharing Scheme (LSSS) for the access structure. It has been observed that the approaches implemented in the existing schemes are computationally expensive and are vulnerable to collusion attacks caused by the cloud and revoked users. Thus, an efficient proxy-based and collusion resistant multi-authority revocable CPABE framework (PCMR-CPABE) is proposed in the current study. The proposed framework is decentralized, dynamic, scalable, and ensures forward/backward secrecy. Additionally, the proposed framework is computationally efficient and is practical to implement as it does not require secret key or group secret key and ciphertext update to address revocation. Furthermore, the incorporation of time and identity-based components allows the proposed framework to resist collusion attacks efficiently.

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