PostHeaderIcon Clock glitches, one of the most important way of IC attack

Clock-signal glitches are currently the simplest and most practical ones. In real application glitches are normally used to replace conditional jump instructions and test instructions preceding them. They create a window of vulnerability in the processing stages of many security cryptographic barriers by simply preventing the execution of the code that detects an unsuccessful authentication attempt. Instruction glitches can also be used to extend the runtime of loops, for example, in serial port output routines to see more of the memory after the output buffer, or to reduce the number of loops in cryptographic operation to transform the cipher into a weak one.

To perform a glitch, the clock frequency should be temporarily increased for one or more half cycles so that some flip-flops sample their input before the new state has reached them. As clock glitches are normally aimed at CPU instruction flow, they are not very effective for devices with hardware implementations of security protection. Therefore it is practical to use clock glitches only when attacking microcontrollers with software programming interfaces or some smartcards.

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