Key-Policy Attribute-Based Encryption Using Pairing-Friendly Curves

The patent segments the attribute-based encryption process by separating the access policy evaluation from the actual decryption operation. The ciphertext is divided into multiple components corresponding to different attributes, and the decryption key is structured to efficiently evaluate the access policy. This segmentation enables parallel processing of attribute matching, significantly improving decryption speed while maintaining security.

The patent changes critical parameters of the encryption scheme by using asymmetric (Type-III) pairing-friendly elliptic curves with optimized group orders. By carefully selecting parameters such as the security parameter λ and the group order p, the patent achieves both high-speed computation and strong security guarantees. The parameter optimization reduces the computational complexity of pairing operations, directly improving encryption and decryption speeds.

The patent extracts and eliminates redundant elements from the ciphertext and key structures. By using a compact representation of attribute encodings and removing unnecessary cryptographic components, the patent reduces ciphertext size by approximately 30% compared to existing schemes. The key structure is optimized by extracting only the essential elements needed for decryption, reducing key sizes while maintaining equivalent security levels.

The patent employs composite cryptographic structures that combine multiple cryptographic primitives into unified, space-efficient formats. The encryption scheme integrates symmetric and asymmetric cryptography, along with hash functions, into a composite structure that achieves strong security guarantees with reduced overall size. This composite approach allows the system to leverage the strengths of different cryptographic methods while minimizing the total data overhead.

The patent creates a universal attribute-based encryption framework that can handle multiple access control policies and attribute types through a single unified interface. The system supports both ciphertext-policy and key-policy ABE modes, as well as various access structures (threshold, AND, OR, hierarchical), using the same core cryptographic primitives. This universality simplifies deployment by eliminating the need for separate implementations of different ABE variants.

The patent introduces an intermediary attribute encoding layer that mediates between the access policy definition and the cryptographic operations. This encoding layer translates high-level access control requirements into cryptographic parameters, shielding users from the underlying complexity. The intermediary structure allows policy administrators to define access controls using intuitive rules rather than complex cryptographic configurations, significantly reducing deployment complexity.