Logic Circuit Authentication with Symmetric and Asymmetric Keys
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Solution Overview
Problem
Current logic circuits in print apparatuses rely primarily on symmetric authentication, making them vulnerable to reverse engineering and emulation, and existing authentication methods are inefficient and costly when combining different types of authentication.
Innovation Solution
Implementing a logic circuitry package with both symmetric and asymmetric authentication mechanisms, where asymmetric device-specific private keys are stored, requiring reverse engineering of each logic circuit, and using a secure communication protocol like I2C to securely connect with a host logic circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If symmetric authentication is used in logic circuits, then ease of operation is improved, but reliability is worsened due to vulnerability to reverse engineering and emulation
Solution Approach 1:
The patent combines symmetric authentication (I2C protocol) with asymmetric authentication (certificate-based) into a unified authentication system. The logic circuit performs both symmetric authentication using shared secrets and asymmetric authentication using device-specific private keys and certificates, merging two authentication paradigms to achieve both ease of operation and high reliability
Solution Approach 2:
The authentication mechanism uses a composite approach by integrating multiple authentication layers: symmetric key-based authentication for efficient operations and asymmetric certificate-based authentication for enhanced security. This composite authentication structure protects against both casual access and sophisticated reverse engineering attacks
2Reliability
If multiple authentication types are combined, then reliability is improved, but device complexity is worsened
Solution Approach 1:
The authentication system is segmented into distinct functional modules: a symmetric authentication module using I2C protocol with shared secrets, and an asymmetric authentication module using device-specific private keys and certificates. This segmentation allows each module to operate independently with optimized complexity for its specific function
Solution Approach 2:
The patent introduces an intermediary certificate structure that mediates between the asymmetric private key and the authentication verification process. The certificate acts as a standardized intermediary that simplifies the interaction between device-specific asymmetric keys and the host system, reducing overall system complexity
3Reliability
If device-specific asymmetric keys are stored, then reliability is improved against reverse engineering, but manufacturing precision is worsened due to key distribution requirements
Solution Approach 1:
Device-specific asymmetric key pairs are generated and certificates are issued during the manufacturing process before the logic circuits are deployed. This preliminary action ensures that each device has its unique cryptographic identity established in advance, enabling secure authentication from the first use without requiring complex post-manufacturing key distribution infrastructure
Data Source
AI summary
A certificate schema for a public key certificate includes a schema identifier field and a root key identifier field. The certificate schema also includes a Cryptographic Mode of Use Attribute (CMA) field and a public key field.