Functional Encryption Ciphertext Transformation for Decryption Efficiency
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Solution Overview
Problem
Attribute-based encryption (ABE) systems face inefficiencies in terms of ciphertext size and decryption time, particularly when dealing with complex access formulas, which can be cumbersome for user equipment with limited computational resources, and outsourcing decryption to a proxy raises security concerns if the user's decryption key is revealed.
Innovation Solution
Transforming functional encryption (FE) ciphertext into partially-decrypted (PD) ciphertext, which is shorter in length or decrypts faster, using a transformation key generated by an authority or a user, and sent over a network to user equipment for decryption, without revealing the decryption key to the proxy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If attribute-based encryption is used to enable policy-based access control, then encryption flexibility and access control capability are improved, but ciphertext size and decryption time increase with formula complexity
Solution Approach 1:
The patent segments the decryption process into two phases: a computationally intensive transformation phase that converts FE ciphertext to PD ciphertext, and a lightweight decryption phase that operates on the transformed ciphertext. This segmentation allows complex access control formulas to be processed efficiently by separating the heavy computation from the final decryption operation.
Solution Approach 2:
The patent performs preliminary transformation of the FE ciphertext into PD ciphertext before the actual decryption operation. This preliminary action pre-processes the ciphertext to remove redundant computational overhead, so that the subsequent decryption by resource-constrained devices requires minimal computation regardless of the original formula complexity.
2Ease of operation
If decryption is outsourced to a proxy to reduce user equipment computational burden, then ease of operation is improved, but security deteriorates due to potential exposure of decryption keys
Solution Approach 1:
The patent extracts the decryption key from the outsourcing process entirely. Instead of giving the key to the proxy, the system transforms the ciphertext structure so that the key remains only at the user device. The proxy performs transformation using only public information and auxiliary data, never accessing the secret key, thus maintaining security while achieving computational outsourcing.
Solution Approach 2:
The patent introduces PD ciphertext as an intermediary form between FE ciphertext and plaintext. This intermediary representation allows the proxy to perform computational work on transformed data without ever needing the decryption key, while the user device can complete the process using only its key and the transformed ciphertext, maintaining security boundaries.
3Loss of information
If FE ciphertext is transmitted to user equipment for decryption, then communication completeness is maintained, but transmission time increases due to large ciphertext size
Solution Approach 1:
The patent segments the ciphertext transmission into two stages: first transmitting the FE ciphertext (which contains all necessary information for decryption), then transmitting the transformed PD ciphertext (which is smaller and faster to process). The segmentation allows the system to maintain complete communication while reducing the burden of transmitting and processing large ciphertexts.
Solution Approach 2:
The patent changes the parameter of ciphertext representation by transforming it from FE format to PD format. This parameter change reduces the effective size and computational complexity of the ciphertext without losing any essential information, enabling faster transmission and processing while maintaining decryption capability.
Data Source
AI summary
Functional encryption (FE) ciphertext is transformed into partially-decrypted (PD) ciphertext. The PD ciphertext has a shorter bit length than the FE ciphertext, or the decryption time of the PD ciphertext is less than the decryption time of the FE ciphertext. The FE ciphertext can be an attribute-based encryption ciphertext. The transformation can be performed with a transformation key generated by an authority with a master key or by a user with a decryption key. The transformation can also be performed, without a transformation key, based on unencrypted components of the FE ciphertext and on auxiliary information associated with the unencrypted components of the FE ciphertext. The PD ciphertext can require less transmission time across a network than the FE ciphertext. The PD ciphertext can require less time to decrypt than the FE ciphertext, particularly when the computational resources performing the decryption are limited.