Pseudonymous Diffie-Hellman Protocol for Secure Portable Data Carrier Authentication
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Solution Overview
Problem
The existing Restricted Identification (RI) protocol for secure communication between portable data carriers and terminals does not allow for individual revocation of a portable data carrier if its CA protocol key is compromised, leading to insecure pseudonym generation and potential impersonation by attackers.
Innovation Solution
A pseudonymous Diffie-Hellman protocol is combined with the CA protocol, using a group key and discrete logarithmic representation to ensure secure communication and prevent attackers from generating pseudonyms for other users, even if the group key is compromised.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the RI protocol is used to generate pseudonyms for secure communication, then secure communication and authentication are achieved, but individual revocation of compromised portable data carriers is not possible
Solution Approach 1:
The system segments the key structure into multiple components: a group key shared by all portable data carriers in a group, and individual secret values specific to each carrier. The public key is constructed as a combination of these segmented components (PK = s*G1 + t*G2), allowing the system to revoke individual carriers by updating their specific secret values while maintaining the group key, thus enabling individual revocation while preserving secure communication.
2Productivity
If a group key is used for the CA protocol to enable contactless communication, then communication efficiency is improved, but security is compromised if the group key is compromised
Solution Approach 1:
The system applies local quality by giving different security properties to different parts of the key structure. The group key provides efficient authentication for all carriers in the group, while individual secret values (s and t) provide unique security identification for each carrier. This allows the system to maintain communication efficiency through the group key while ensuring security through individual secrets that can be independently compromised or revoked.
Solution Approach 2:
The public key is constructed as a composite structure combining multiple cryptographic elements: PK = s*G1 + t*G2, where s and t are individual secrets and G1 and G2 are group elements. This composite key structure allows the system to leverage the efficiency of group-based authentication while incorporating individual security properties, resolving the contradiction between communication efficiency and security.
3Reliability
If the CA protocol key is compromised, then all portable data carriers in the same group must be revoked, but this is not user-friendly
Solution Approach 1:
The system implements dynamic key management where the key structure can adapt to compromise scenarios. When a carrier is compromised, the system can update that specific carrier's individual secret values (s and t) without affecting other carriers in the group. This dynamic approach allows selective revocation and reissuance of individual carrier credentials, making the system both secure and user-friendly.
Data Source
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AI summary
By combining the CA protocol with the RI protocol, a pseudonymous Diffie-Hellman protocol is provided. According to the invention, the pseudonym is determined from the RI protocol, and in a substantially parallel manner the secured communication channel is formed from the CA protocol. According to the invention, a group key for the CA part of the protocol according to the invention is likewise used. By virtue of the design of the protocol according to the invention, even if an attacker has succeeded in ascertaining the group key of a portable data carrier according to the invention, it would be impossible for the attacker to generate the pseudonym of another user, in contrast to the known protocols.