Portable Data Storage Authentication via Dynamic Session Keys
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Solution Overview
Problem
Existing methods for authenticating portable data carriers compromise user anonymity and incur significant costs and efforts when one data carrier is compromised, as personalized key pairs lead to traceable user movements and require group replacement.
Innovation Solution
A method using a group public key and a secret key derived from a secret group key, where the secret key is replaced by a session-specific key for each authentication, ensuring anonymity by making each data carrier indistinguishable and preventing tracking, without the need to store the secret group key.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If each data carrier is personalized with an individual pair of keys, then authentication security is improved, but user anonymity deteriorates and tracking becomes possible
Solution Approach 1:
The secret key material is segmented into two parts: a static secret group key stored on the data carrier and a dynamic session-specific key component generated during authentication. This segmentation allows the static part to provide consistent authentication while the dynamic part prevents tracking, resolving the contradiction between security and anonymity.
Solution Approach 2:
The authentication system transitions from static individual keys to dynamic session-specific keys. Each authentication session generates a unique key pair derived from the static group key, making the authentication credentials dynamic rather than static. This enables both secure authentication and user anonymity, as the same data carrier presents different cryptographic identities in different sessions.
2Loss of information
If a group key pair is used to restore anonymity, then user tracking is prevented, but security deteriorates as compromise of one carrier compromises the entire group
Solution Approach 1:
The group key pair is segmented such that only the public group key is shared among all data carriers, while each carrier has its own unique secret group key stored securely. This segmentation isolates the secret material to individual carriers, so compromise of one carrier's public key does not expose other carriers' secret keys, maintaining both anonymity and security.
Solution Approach 2:
A certificate authority acts as an intermediary to issue certificates that bind public group keys to identifiable entities. This allows the system to maintain anonymity during authentication (using unsigned public group keys) while providing a mechanism for legitimate identification when needed (through verified certificates), without compromising the security model.
3Reliability
If session-specific keys are used for each authentication, then anonymity is preserved and security is maintained, but device complexity increases
Solution Approach 1:
The static secret group key and public group key are preliminarily established and stored on the data carrier during manufacturing or initialization. This preliminary action eliminates the need for complex key generation during each authentication session, reducing operational complexity while maintaining the security benefits of session-specific keys.
Solution Approach 2:
The data carrier autonomously generates its own session-specific key pairs during authentication using its stored secret group key, without requiring external key management infrastructure. This self-service capability simplifies the overall system architecture by eliminating the need for a centralized key distribution system, offsetting the increased cryptographic complexity with reduced operational overhead.
Data Source
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AI summary
A method for authenticating a portable data storage medium (10) to a terminal device involves the use of a public key (PKG) and a secret key (SK1) from the data storage medium (10) and of a public session key (??T) and a secret session key (SKT) from the terminal device. The data storage medium (10) uses a public group key (PKG) as a public key. As a secret key the data storage medium (10) uses a key (SK1) which has been derived from a secret group key (SKG) associated with the public group key (PKG).