Biometric Digital Signing With MPC and Cancelable Templates
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Solution Overview
Problem
Existing digital signature methods requiring cryptographic keys stored in devices exclude individuals without such devices, and biometric signatures face issues with randomness, inaccuracy, and vulnerability to identity theft, while lacking privacy-preserving mechanisms.
Innovation Solution
A method utilizing secure multi-party computation, cancelable biometric templates, and private information retrieval allows users to digitally sign messages using biometric samples without storing cryptographic keys on devices, ensuring privacy and security by keeping biometric information and secret keys hidden from all entities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If biometric samples are used for digital signatures, then accessibility for individuals without cryptographic devices is improved, but security and privacy are worsened due to randomness and inaccuracy in biometric readings
Solution Approach 1:
The secret key is divided into multiple shares distributed across different parties (user, server, custodian). Each party holds only a portion of the key, and no single party can forge signatures alone. This segmentation eliminates the single point of failure while maintaining accessibility for users without storing complete cryptographic keys on their devices.
Solution Approach 2:
A custodian is introduced as an intermediary party who holds additional key shares and can intervene when biometric authentication fails. The custodian acts as a mediator between the user and the server, providing backup authentication capability while maintaining security through distributed key management.
2Ease of operation
If biometric information is stored even under encryption, then accessibility for authentication is improved, but privacy is worsened as malicious actors could store encrypted biometric information for long time
Solution Approach 1:
The raw biometric data is extracted and processed locally at the user's device to generate a biometric template. Only this derived template is stored and transmitted, never the original biometric sample. This extraction eliminates the risk of storing sensitive biometric information while maintaining authentication capability.
Solution Approach 2:
The biometric data is transformed through cryptographic operations (hashing, salting) to change its parameter representation. The original biometric parameters are never stored; only transformed versions are kept. This parameter change ensures that even if stored data is compromised, the original biometric information remains protected.
3Adaptability or versatility
If cancelable biometric templates are used, then adaptability for biometric replacement is improved, but complexity of the system is worsened
Solution Approach 1:
The biometric template is made dynamic and revocable rather than static. When compromise is detected or needed, the template can be cancelled and regenerated without affecting the underlying biometric data or requiring reissuance of cryptographic keys. This dynamic property allows flexible adaptation while maintaining security.
Solution Approach 2:
Multiple biometric templates are pre-generated and stored during registration. When a template needs to be cancelled, alternative templates are already prepared and can be activated immediately. This preliminary preparation enables smooth transitions during biometric replacement without system complexity spikes.
4Reliability
If secret sharing and MPC are employed to eliminate single point of failure, then security is improved, but device complexity and computational overhead are worsened
Solution Approach 1:
The computational burden of secret sharing is segmented across multiple parties. Each party performs only local computations on their key shares rather than processing the entire key. This segmentation reduces individual computational complexity while maintaining overall system security.
Solution Approach 2:
Instead of requiring complex real-time MPC protocols for every operation, pre-computed key shares and authentication data are copied and cached at each party. This allows simpler, faster operations using copied data while maintaining the security benefits of distributed key management.
Data Source
AI summary
The present invention provides a method for digitally signing an electronic message in a secure, privacy-preserving, and device-free manner by presenting a biometric probe to a computer terminal, where the biometric probe never leaves the terminal, and any data leaving the terminal cannot reveal the presented biometric characteristics. The user's biometric sample is converted into a cancelable biometric template (CBT) and initiates multi-party computation (MPC) with a set of computer servers to perform a key inception algorithm and distribute secret shares to the participating servers, as well as to generate relevant parameters. Once registered, the user may present a biometric probe on another computer terminal and retrieve the account parameters using a privacy-preserving method. The account parameters are used with the biometric probe to produce a digital signature by performing MPC. Custodian servers may participate in this method to allow for alternative identification.