Bus Probing Detection via Phase Shift Monitoring
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Solution Overview
Problem
Existing methods for detecting bus probing/tampering in computer systems are either invasive, require system halt for detection, or impose significant latency and power overhead, making them unsuitable for runtime protection.
Innovation Solution
A method that detects phase shifts in the output waveform of a bus transmitter, induced by changes in input impedance, using a circuit with a flip flop to track metastability, allowing for runtime detection without interrupting normal data transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data encryption is used to protect data privacy during transfer, then data security is improved, but latency and power consumption increase significantly
Solution Approach 1:
The patent introduces an intermediary detection circuit that monitors impedance changes on the bus without requiring full encryption/decryption operations. This intermediary monitoring mechanism provides security verification with minimal latency impact by detecting probing attacks through electrical characteristic changes rather than cryptographic verification of every data transfer.
2Reliability
If full data encryption is implemented on high-speed buses, then data security is improved, but power consumption increases significantly
Solution Approach 1:
The patent applies partial protection by monitoring only the electrical impedance characteristics of the bus rather than encrypting all data transfers. This partial action approach provides adequate security against probing attacks while avoiding the excessive power consumption of full encryption/decryption operations on every data transfer.
3Measurement precision
If impedance change detection is performed by introducing controlled DRAM write errors, then probing detection is achieved, but system operation must be halted adding significant latency
Solution Approach 1:
The patent enables continuous bus operation by detecting impedance changes through dedicated monitoring circuitry that operates in parallel with normal data transfers. The detection process does not require halting system operations or introducing write errors, maintaining continuous productive action while providing probing detection.
4Measurement precision
If multiple external circuit components are used for probing detection, then detection capability is improved, but device complexity and implementation difficulty increase
Solution Approach 1:
The patent merges the probing detection function with the existing bus transmitter circuitry by detecting impedance changes at the transmitter output. This integration approach combines multiple functions into a unified circuit structure, reducing the need for separate external detection components and simplifying overall system implementation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables zero-latency, runtime detection of both on-chip and off-chip bus probing attacks on single-ended and differential buses, scalable and requiring minimal computational resources, potentially eliminating the need for data encryption.
Implementation Method 1
The detecting step is preferably performed by a circuit comprising a flip flop. The method preferably comprises delaying the output waveform, thereby placing the flip flop into a metastable state prior to use of the bus.
Data Source
AI summary
Methods and apparatuses for detection of probing attacks or other tampering on any bus, including on chip and off chip buses. The method can be performed during runtime, concurrently with normal data transfer on the bus, without stopping the normal data transfer, and without imposing any latency to communications on the bus. The tampering or attack is detected by detecting a phase shift between the input waveform and the output waveform of the bus transmitter. The phase shift is induced by an input impedance change at the output of the bus transmitter caused by the tampering. The phase shift can be measured by detecting a change in the output probability of a metastable flip flop.