Metal Shield Circuit With LFSR Signals for Tamper Detection
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Solution Overview
Problem
There is a need for effective detection systems to prevent tamper attacks on secure devices, particularly those that utilize focused ion beam (FIB) access to breach metal layers and access confidential data, as existing security measures are inadequate in detecting such breaches.
Innovation Solution
A tamper detection circuit is implemented using metal shield wires driven by a 16-bit linear feedback shift register (LFSR) to provide random and unique signal values, which are monitored for connectivity breaks, generating an alarm signal upon detection of any breach, and optimized for area and power efficiency by enabling the shield system only when needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal shield wires are monitored for tamper detection, then security detection capability is improved, but device complexity increases
Solution Approach 1:
The circuit is divided into functional segments: LFSR for random signal generation, metal shield wires for physical monitoring, XOR gates for comparison, and alarm logic for breach detection. Each segment performs a specific function, making the overall system manageable despite complexity
Solution Approach 2:
The metal shield wires serve dual purposes: they provide electromagnetic shielding for the secure region and simultaneously act as sensor elements for tamper detection. This multi-functionality reduces the need for separate detection infrastructure
2Measurement precision
If LFSR-driven random signals are used on metal shield wires, then detection precision is improved, but power consumption increases
Solution Approach 1:
The LFSR generates periodic random sequences that are clocked at specific intervals. The system monitors these periodic signals and can enter low-power states between monitoring cycles, reducing overall power consumption while maintaining detection precision
Solution Approach 2:
The system uses simple digital logic components (XOR gates, latches) that consume minimal power compared to continuous analog monitoring. The random signals are regenerated periodically rather than maintained continuously, reducing power usage
3Use of energy by moving object
If shield system is enabled only when needed, then power efficiency is improved, but response time may worsen
Solution Approach 1:
The LFSR is pre-configured with seed values and ready to generate random sequences immediately when the shield system is enabled. The metal shield wires are physically in place and electrically connected beforehand, so detection can begin instantly upon activation without warm-up delays
Data Source
AI summary
According to one implementation of the present disclosure, a circuit includes: two or more metal wires, respective XOR gates coupled to each of the two or more top metal wires, a shift register having outputs coupled to the XOR gates, an OR gate configured to receive each of the outputs of the XOR gates, and a latch configured to receive an output of the OR gate and transmit an output signal corresponding to an alarm signal.