Constant Ciphertext Length in CP-ABE
This addresses efficiency issues in attribute-based encryption for applications requiring compact ciphertexts, though it is incremental as it focuses on a specific threshold case.
The paper tackles the problem of ciphertext size growing linearly with the number of attributes in CP-ABE by proposing a scheme that maintains constant ciphertext length for threshold policies, with security based on the Decisional Bilinear Diffie-Hellman problem.
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.