Cryptographic Method Using Static Public Key and Derived Secret Key
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Solution Overview
Problem
Existing cryptographic methods for portable data carriers and terminal devices lack robust authentication mechanisms, leading to security vulnerabilities and inability to ensure user anonymity, as they rely on storing secret keys and passwords, which can be compromised.
Innovation Solution
A cryptographic method using a static public key and a derived secret key, where the secret basic key is not stored in the data carrier, and a session-specific secret key is used for each operation, ensuring that even if one data carrier is compromised, others in the group remain secure, and user anonymity is maintained through the use of a public group key.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If secret keys and passwords are stored on the data carrier for authentication, then authentication functionality is enabled, but security vulnerabilities arise and user anonymity cannot be ensured
Solution Approach 1:
The patent extracts the secret basic key from the data carrier storage. Instead of storing the secret basic key on the data carrier, the system uses a static public key that remains on the carrier while the secret key is kept external or in memory only during operation. This extraction eliminates the security vulnerability of stored secret keys while maintaining authentication functionality through the public key infrastructure.
Solution Approach 2:
The patent implements dynamic session-specific secret keys that are generated for each operation rather than using static stored keys. This dynamic approach ensures that even if one session key is compromised, other sessions remain secure, and the static public key on the data carrier cannot be used to derive past or future secret keys, thereby ensuring user anonymity and preventing key extraction attacks.
2Ease of operation
If a static secret key is stored on the data carrier for cryptographic operations, then authentication is simplified, but the system becomes vulnerable to key extraction and compromise
Solution Approach 1:
The patent removes the static secret key from the data carrier storage entirely. The data carrier retains only the static public key, which cannot be used to derive the secret key. This extraction simplifies the storage requirements on the carrier while dramatically improving security by eliminating the attack surface of stored secret keys.
Solution Approach 2:
The patent introduces session-specific secret keys as intermediaries between the static public key on the carrier and the actual cryptographic operations. These temporary keys enable authentication operations without exposing the fundamental secret basic key, maintaining operational simplicity while ensuring key security through multiple layers of abstraction.
3Productivity
If the same secret key is used across multiple sessions, then authentication efficiency is improved, but user anonymity is lost and security is compromised
Solution Approach 1:
The patent implements dynamic session-specific secret keys that change with each authentication session. While this increases computational overhead compared to reusing a single key, it preserves user anonymity by preventing tracking across sessions and maintains security through forward secrecy. The static public key on the carrier enables efficient verification without revealing session-specific secrets.
Solution Approach 2:
The patent segments the authentication key material into a static public key component (on the carrier for efficient identification) and dynamic secret key components (session-specific for anonymity and security). This segmentation allows the system to maintain authentication efficiency through the static public key while preserving anonymity through segmented, non-reusable secret keys.
Data Source
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AI summary
In a cryptographic method, between a portable data carrier (10) and a terminal device, a public data carrier key (PKG) and a secret data carrier key (SK1) of the data carrier (10) as well as a public terminal key (PKT) and a secret terminal key (SKT) of the terminal device are used. The data carrier (10) uses a static public key as the public data carrier key (PKG). As a secret data carrier key (SK1), the data carrier (10) uses a secret key which is derived from a secret basic key (SKG) associated with the public data carrier key (PKG). In the context of the method, the terminal device checks an authentication parameter (AP) which is associated with the data carrier (10) and which is different from the data carrier keys.