Lattice-Based Blind Signature Using Commitment Mediator
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Solution Overview
Problem
Existing lattice-based blind signature schemes face challenges in proving knowledge of a signature without revealing the message, especially when hash functions are involved, leading to inefficiencies and unproven security.
Innovation Solution
The method involves a user device generating a commitment for a message and transmitting it to a signer device, which uses a secret trapdoor function to sample a short vector solving a lattice problem. The user device then verifies this short vector and generates a signature establishing knowledge of it based on the message and public data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lattice-based cryptographic schemes are used for blind signatures, then security against quantum attacks is improved, but complexity of proving knowledge of signature increases
Solution Approach 1:
The patent introduces a commitment scheme as an intermediary mechanism between the lattice-based signature and the zero-knowledge proof. The commitment c=com(m,r) serves as a mediator that allows the prover to demonstrate knowledge of the signature without directly proving knowledge of the lattice secret, thereby reducing proof complexity while maintaining quantum security
Solution Approach 2:
The blind signature protocol is segmented into distinct phases: commitment generation, signing, and verification. The knowledge proof is further segmented to prove knowledge of the commitment opening and the signature separately, making the overall proof process more manageable and less complex
2Ease of operation
If hash functions are involved in lattice-based blind signatures, then signature generation is enabled, but security proofs become unproven
Solution Approach 1:
The patent replaces the traditional hash function mechanism with a lattice-based commitment mechanism. Instead of relying on hash functions that lack proven security in the quantum random oracle model, the system uses lattice-based commitments with proven security reductions, thereby maintaining ease of operation while establishing reliable security proofs
3Device complexity
If traditional blind signature schemes are used, then simplicity is maintained, but quantum security is compromised
Solution Approach 1:
The patent changes the fundamental parameters of the cryptographic system from classical discrete logarithm-based assumptions to lattice-based assumptions. This parameter change enables quantum security while maintaining protocol simplicity through the use of standard cryptographic primitives adapted to the lattice setting, such as lattice-based commitments and lattice-based zero-knowledge proofs
Data Source
AI summary
There is disclosed provided a computer-implemented method of generating a signature for a message. A user device processes the message and random data to generate a commitment for the message, and transmits the commitment to a signer device. The signer device derives a target vector from the commitment and samples, using a secret trapdoor function, a short vector that solves a lattice problem involving the target vector. The signer device then sends the short vector to the user device, which verifies that the short vector solves the lattice problem. Following successful verification of the short vector, the user device generates a signature establishing knowledge of the short vector based on the message and public data.