Functional Proxy Re-Encryption Key Generation
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Solution Overview
Problem
Current proxy re-encryption schemes are limited in that they can only delegate decryption rights to a single user or users with restricted attributes, lacking flexibility in selecting third parties for re-encryption.
Innovation Solution
A cryptographic system implementing a functional proxy re-encryption (FPRE) scheme that generates a re-encryption key allowing decryption of ciphertexts by converting decryption keys and embedding a non-monotonic access structure, enabling flexible forwarding of ciphertexts to various types of users.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a traditional proxy re-encryption scheme is used, then decryption rights can be delegated to third parties, but the delegation is limited to a single user or users with very restricted attributes
Solution Approach 1:
The re-encryption key is designed to serve multiple functions simultaneously: it enables re-encryption to a single user, to multiple users, and to users matching specific attribute patterns. The key structure incorporates wildcard characters and attribute specifications that allow it to function as a universal delegation instrument rather than requiring separate keys for each delegation scenario.
Solution Approach 2:
The system changes the parameters of the re-encryption key by incorporating attribute specifications and wildcard patterns directly into the key structure. This allows the key to dynamically match different user attribute sets, transforming a static key into a parameterized key that adapts to various delegation scenarios without requiring multiple distinct keys.
2Reliability
If multiple re-encryption keys are generated for different users, then each user can be delegated securely, but the system complexity and key management overhead increase
Solution Approach 1:
Multiple delegation functions are merged into a single re-encryption key. The key structure combines attribute specifications, wildcard patterns, and re-encryption logic into one unified object, eliminating the need to manage multiple separate keys for different users or user groups while maintaining security through the mathematical properties of the underlying cryptographic scheme.
3Adaptability or versatility
If attribute-based encryption is used, then access control can be specified, but only AND and negative elements can be specified for ciphertexts
Solution Approach 1:
The access structure specification is made dynamic by incorporating wildcard characters and pattern matching into the re-encryption key. Instead of being restricted to static AND and negative logic, the system allows dynamic attribute matching where wildcards can represent any attribute value, enabling OR logic, prefix matching, and other complex access patterns that adapt to different delegation scenarios.
Data Source
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AI summary
It is an object to implement a functional proxy re-encryption scheme. A decryption device 300 transmits to a re-encryption device 400 a decryption key k*rk which is generated by converting, using conversion information W1, a decryption key k* in which is set one of attribute information x and attribute information v corresponding to each other, and encrypted conversion information ψrk which is generated by encrypting the conversion information W1 with one of attribute information x' and attribute information v' corresponding to each other being set. The re-encryption device 400 generates a re-encrypted ciphertext CT, constituted by a ciphertext crenc which is generated by setting at least one of additional information H and additional information Θ corresponding to each other in a ciphertext cenc in which is set the other one of the attribute information x and the attribute information v, and a decryption key k*renc which is generated by setting at least the other one of the additional information H and the additional information Θ in the decryption key k*rk.