PLC Program Verification Using Shared Confidential Codes
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Solution Overview
Problem
Existing programmable logic controller (PLC) systems lack security measures to prevent corruption or tampering of control programs acquired from external sources, potentially leading to unintended and inappropriate processes.
Innovation Solution
A control system that includes a programmable controller and a program transmission apparatus, which generates and verifies unique codes for control programs using confidential data to ensure integrity, allowing only authorized and unaltered programs to be executed by the PLC.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a PLC independently acquires a program from an external source, then the ease of operation is improved, but the security is worsened due to potential corruption or tampering of the transmitted program
Solution Approach 1:
The patent applies preliminary action by generating a verification code (hash value) in advance at the transmission side before sending the control program. This verification code is transmitted together with the program and will be used later for validation, preventing tampering issues before they can occur during program execution.
Solution Approach 2:
The patent implements feedback by having the PLC generate a verification code from the received program using the same hash function and confidential data, then compare it with the transmitted verification code. This feedback mechanism confirms program integrity by detecting any alterations that occurred during transmission or storage.
2Reliability
If a verification mechanism is added to ensure program integrity, then the reliability is improved, but the device complexity increases due to additional code generation and verification steps
Solution Approach 1:
The patent replaces complex mechanical or procedural verification systems with a mathematical hash function-based verification mechanism. This substitution uses computational algorithms (SHA-256 or similar) to generate and verify program integrity codes, which is more efficient and less complex than traditional manual or hardware-based verification methods.
Solution Approach 2:
The patent changes the parameter of verification from potentially complex multi-step processes to a simple hash value comparison. By transforming the verification problem into a mathematical parameter (hash code) that can be easily generated and compared, the system achieves high reliability with minimal added complexity.
Data Source
AI summary
The control system (1000) includes a programmable logic controller (PLC) (40) to control a device, and a program transmission apparatus (10) to transmit a control program (70) for causing the PLC (40) to control the device. The program transmission apparatus (10) includes a first code generator (113) to generate a first code (71) for verification of presence or absence of a change from the control program (70) by using the control program (70) and confidential data (80). The PLC (40) includes a second code generator (433) to generate a second code by using a receiving program as the control program (70) and the confidential data (80) that is shared with the program transmission apparatus (10), and an executor (435) to execute the receiving program when the first code (71) is identical to the second code.