CPABE

CP-ABE, or Ciphertext-Policy Attribute-Based Encryption, is an encryption paradigm where access control is embedded into the ciphertext. In CP-ABE, a trusted attribute authority issues secret keys to users bound to a set of attributes (for example, department=cardiology, clearance=high). The ciphertext is created with an access policy describing which attribute combinations are allowed to decrypt. A user can decrypt only if their attributes satisfy the policy, meaning no information about non-authorized attributes is leaked.

The scheme typically relies on pairing-based cryptography. The access policy is represented as a monotone Boolean formula or an access tree; encryption uses this policy to produce the ciphertext, and decryption requires the user’s attribute keys to satisfy the policy to recover the plaintext. The authority’s private keys tie to individual attributes, enabling fine-grained control without sharing decryption keys for all data.

CP-ABE was introduced by Bethencourt, Sahai, and Waters in 2007. It is one of the core frameworks of attribute-based encryption, alongside variants such as KP-ABE. Many improvements have addressed efficiency, scalability, and revocation, including hybrid encryption approaches and dynamic policy updates. Security analyses typically prove IND-CPA-like security under standard cryptographic assumptions, assuming a trusted attribute authority and secure key distribution.

Applications include secure data sharing in cloud storage, electronic health records, government or enterprise collaboration, and Internet of Things scenarios requiring fine-grained access control. Limitations include complex key management, revocation, and potential single-point-of-trust in the authority, plus computational and communication overhead compared with traditional public-key schemes. Some CP-ABE schemes are not post-quantum secure.