JTAG Authentication Circuit Preventing Unauthorized Access
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Solution Overview
Problem
JTAG-compliant devices can be misused for illicit purposes, and correcting the TAP controller to address this is risky and often not feasible, necessitating a new authentication method that does not require modifying existing circuits.
Innovation Solution
An apparatus with a JTAG access circuit that determines whether to access a JTAG-compliant device using a predetermined protocol, inactivating and activating inner bus lines and units based on recognition data consistency, thereby authenticating the device without altering existing circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the TAP controller is corrected to prevent unauthorized access, then security is improved, but the risk of circuit modification increases and may not be feasible
Solution Approach 1:
The patent segments the JTAG system into two parts: the original TAP controller (unchanged) and a new authentication circuit. The authentication circuit operates independently to verify device identity before allowing JTAG access, thus preventing unauthorized access without modifying the original TAP controller circuits.
Solution Approach 2:
The patent introduces an intermediary authentication circuit that mediates between the JTAG interface and the inner units. This authentication circuit verifies device identity and controls access to inner bus lines and units, preventing unauthorized access without requiring modifications to the original TAP controller.
2Ease of operation
If the JTAG access is always allowed for debugging purposes, then ease of operation is improved, but the risk of illicit usage increases
Solution Approach 1:
The patent performs preliminary authentication before allowing JTAG access to inner units. The authentication circuit verifies the device identity in advance by comparing recognition data with reference data, and only after successful authentication does it enable access to inner bus lines and units. This ensures that debugging access is provided conveniently to authorized devices while preventing illicit usage.
Solution Approach 2:
The authentication circuit provides feedback by continuously monitoring the JTAG interface and verifying device identity. When unauthorized access attempts are detected or authentication fails, the circuit responds by maintaining the inactive state of inner bus lines and units, thus preventing illicit usage while allowing legitimate debugging operations.
3Reliability
If authentication circuits are added to prevent unauthorized access, then security is improved, but device complexity increases
Solution Approach 1:
The patent merges the authentication function with the existing JTAG interface structure. The authentication circuit is integrated into the JTAG system and utilizes the existing TAP controller and bus structure, adding minimal new components while achieving enhanced security. The authentication circuit controls access to inner units by managing the activation of inner bus lines, combining security functionality with the existing architecture.
Data Source
AI summary
In an apparatus including a joint test action group (JTAG) authentication device, and a JTAG authentication method using the apparatus, the apparatus includes a joint test action group (JTAG) authentication device, the apparatus comprising a JTAG access circuit that determines whether to access a JTAG-compliant device according to a predetermined protocol that governs the JTAG-compliant device and the apparatus, wherein the JTAG access circuit at least one of inactivates at least one of inner bus lines and inner units and activates the at least one of the inner bus lines and the inner units according to whether the JTAG-compliant device is accessed.