Constant Ciphertext Length in CP-ABE

TL;DR

This paper introduces a CP-ABE scheme where ciphertext size remains constant regardless of attribute number, improving efficiency for attribute-based encryption systems.

Contribution

It presents a novel CP-ABE scheme with fixed ciphertext length for threshold policies, based on the DBDH problem, reducing computational overhead.

Findings

Ciphertext size is constant regardless of attribute count.

The scheme is secure under the DBDH assumption.

Efficient decryption with fewer pairing operations.

Abstract

Ciphertext policy attribute based encryption (CP-ABE) is a technique in which user with secret key containing attributes, only able to decrypt the message if the attributes in the policy match with the attributes in secret key. The existing methods that use reasonably computable decryption policies produce the ciphertext of size at least linearly varying with the number of attributes with additional pairing operations during encryption and decryption. In this paper, we propose a scheme in which ciphertext remains constant in length, irrespective of the number of attributes. Our scheme works for a threshold case: the number of attributes in a policy must be a subset of attributes in a secret key. The security of propose scheme is based on Decisional Bilinear Diffie-Hellman (DBDH) problem.