Inner-Product Functional Encryption Variable-Length Vector Handling
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Solution Overview
Problem
The existing Inner-Product Functional Encryption (IPFE) scheme has fixed maximum lengths for vectors, making it difficult to handle ciphertexts and secret keys of varying lengths, leading to inefficiencies when the lengths are not predetermined during the setup phase.
Innovation Solution
The proposed solution includes a decryption device that acquires and decrypts ciphertexts and secret keys of variable lengths using encryption and key setting information generated based on public information of a fixed size, allowing for the calculation of inner-product values without restricting the maximum length of ciphertexts and secret keys.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the maximum lengths of vectors are fixed by master keys generated in a setup phase, then the scheme can be implemented with fixed parameters, but ciphertexts and secret keys exceeding the fixed lengths cannot be handled
Solution Approach 1:
The patent applies dynamics by making the encryption setting information and key setting information variable in size depending on the vector length, rather than fixed. The master key generation unit generates encryption setting information of a size depending on the size of the vector to be encrypted, and similarly for key setting information. This dynamic adaptation allows the system to handle vectors of any length while maintaining security.
2Adaptability or versatility
If the maximum lengths of ciphertext and secret key are set to be very long to handle any case, then the scheme can handle vectors of any length, but unnecessary degradation in efficiency occurs
Solution Approach 1:
The patent applies parameter changes by adjusting the size of encryption setting information and key setting information according to the actual vector length. Instead of using a fixed large size for all cases, the system dynamically changes the parameter size to match the required vector length, thereby avoiding the efficiency degradation that would result from unnecessarily large fixed sizes while still maintaining the capability to handle vectors of any length.
3Reliability
If encryption setting information and key setting information are generated using public information of fixed size, then the system maintains security through randomized generation, but the information size must adapt to vector size
Solution Approach 1:
The patent applies segmentation by dividing the encryption setting information and key setting information into segments that correspond to the vector elements. Each segment is generated using the public information through randomized processes, and the total size adapts to the vector size. This segmentation approach allows the system to maintain security through randomized generation while managing the information size in a structured way that reflects the actual data requirements.
Data Source
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AI summary
An inner-product functional encryption scheme in which the maximum length of a ciphertext and the maximum length of a secret key are not restricted can be constructed. An encryption device (20) generates a ciphertext ctx in which a vector x is encrypted, using encryption setting information that is of a size depending on the size of the vector x and is generated using as input public information of a fixed size. A key generation device (30) generates a secret key sky in which a vector y is set, using key setting information that is of a size depending on the size of the vector y and is generated using as input the public information. A decryption device (40) decrypts the ciphertext ctx with the secret key sky to calculate an inner-product value of the vector x and the vector y.