RNG Testing Circuit Verification via Register Comparison
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Solution Overview
Problem
It is challenging to reliably test random number generators (RNGs) for 'stuck' conditions, where they output the same data repeatedly, due to the rarity of such failures, leading to uncertainty in the reliability of testing circuits and potential false senses of security.
Innovation Solution
A method and apparatus that simulate a faulty RNG by storing and comparing RNG output values in registers, using sequential and combinational logic to assert a failure signal, allowing for the testing of RNG testing circuits even when the RNG is not faulty, thereby validating the testing and response functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a RNG is tested by comparing consecutive output values, then the testing circuit can detect stuck conditions, but the rarity of actual failures makes it difficult to verify the reliability of the testing circuit itself
Solution Approach 1:
Instead of testing the RNG tester with a faulty RNG (which is rare), the patent inverts the approach by using a known good RNG and intentionally creating faulty test conditions through controlled manipulation of register values. This allows the testing circuit to be verified under known failure conditions without requiring an actually faulty RNG.
Solution Approach 2:
The patent performs preliminary actions by pre-configuring the test system with known good RNG output and intentionally setting register values to create expected failure conditions. This preliminary setup allows the testing circuit's reliability to be verified before actual RNG operation, by simulating failure scenarios that would otherwise be rare or unpredictable.
2Reliability
If sequential and combinational logic are used to simulate faulty RNG conditions, then the testing circuit can be validated, but the complexity of the test apparatus increases
Solution Approach 1:
The patent introduces intermediary elements (registers and control logic) that mediate between the good RNG and the testing circuit. These intermediaries allow controlled manipulation of test data to simulate failure conditions without requiring an actually faulty RNG, thereby validating the testing circuit while keeping the overall system manageable in complexity.
Solution Approach 2:
The patent creates copies of RNG output values in registers and manipulates these copies to simulate faulty conditions. By working with copied and controlled versions of the data rather than requiring an actual faulty RNG, the system can validate the testing circuit's response to failures without the complexity of generating or sourcing genuinely defective RNG hardware.
Data Source
AI summary
A method and apparatus for testing operation of a random number generator (RNG) testing circuit are provided. In accordance with at least one embodiment, a first RNG output value obtained from a RNG is stored in a first register. In response to activation of a test mode to simulate a faulty RNG, the first RNG output value is stored in a second register. The first RNG output value in the first register is compared to the first RNG output value in the second register. In response to the comparing, a RNG failure signal is provided at a RNG testing circuit output of the RNG testing circuit. In accordance with at least one embodiment, sequential and combinational logic can simulate a faulty RNG. Accordingly, simulation of a faulty RNG may be performed to test a RNG testing circuit even when the RNG is not faulty.