Biometric Authentication Malformed Ciphertext Defense
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Solution Overview
Problem
Existing biometric authentication systems using Functional Encryption (FE) or Homomorphic Encryption (HE) are vulnerable to illegal ciphertext attacks, where malicious users can authenticate by sending malformed ciphertexts that produce zero or low distances with any other ciphertext, violating encryption scheme guarantees.
Innovation Solution
During user enrollment, additional randomly generated biometric templates are created and encrypted, which are stored on the server. During authentication, the server checks the new template against these templates, ensuring that distances meet specific requirements, such as being greater than a threshold or adhering to geometric invariants like the triangle inequality, to prevent malicious ciphertexts from producing low distances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If FE or HE systems are used for privacy preserving biometric authentication, then user privacy is protected, but the system becomes vulnerable to malformed ciphertext attacks
Solution Approach 1:
The system performs preliminary actions by generating multiple random templates during enrollment that are guaranteed to be at a sufficient distance from the user's biometric template. These templates are stored and used during authentication to detect malformed ciphertexts before they can compromise the system, preventing the harmful effect in advance.
Solution Approach 2:
The system applies preliminary anti-action by creating random templates specifically designed to counteract potential malformed ciphertext attacks. These templates serve as a defensive mechanism that actively prevents attackers from successfully injecting malicious ciphertexts that would produce falsely low distance values.
2Reliability
If additional random templates are generated and stored during enrollment, then security against malformed ciphertext attacks is improved, but system complexity increases
Solution Approach 1:
The system segments the authentication verification process by checking distances against multiple random templates rather than a single template. This segmentation distributes the security verification across multiple independent checks, making the overall system more robust while maintaining a clear, modular structure that manages complexity.
Solution Approach 2:
The system changes the parameter of template quantity from one to multiple during enrollment. By adjusting this parameter and establishing clear distance threshold requirements, the system enhances security against malformed ciphertext attacks while maintaining manageable complexity through well-defined parameter constraints.
3Reliability
If distance computations are performed on encrypted templates, then privacy is preserved, but the ability to detect malformed ciphertexts is reduced
Solution Approach 1:
The system introduces random templates as intermediaries between the encrypted biometric template and the distance computation process. These intermediary templates enable the server to perform distance computations on encrypted data while still detecting malformed ciphertexts, bridging the gap between privacy preservation and attack detection capability.
Data Source
AI summary
Embodiments may include techniques to prevent illegal ciphertexts using distance computations on homomorphic and/or functional encrypted templates while detecting whether the resulting distance does not meet requirements for validity. For example, a method may comprise receiving and storing enrollment information from a client computer system, the enrollment information comprising an encrypted enrollment template of authentication data and a plurality of randomly generated encrypted templates, receiving an additional encrypted template to be used to authenticate the user from the client computer system, authenticating the user by determining distances between the received additional encrypted template and the stored encrypted enrollment template and the each of the stored plurality of randomly generated encrypted templates, and determining that authentication is successful when the received additional encrypted template meets distance requirements relative to the stored encrypted enrollment template and the each of the stored plurality of randomly generated encrypted templates.