Side-Channel Attack

A side-channel attack recovers a secret by measuring what a device does rather than by breaking the mathematics it does it with. Power draw, timing, electromagnetic emission, sound and even temperature vary with the data being processed, so an attacker with the device on a bench can repeat an operation thousands of times and infer the key bit by bit. Deliberately disturbing the chip — a voltage or clock glitch at the right instant — belongs to the same family, because the goal is to make it skip a check or leak an intermediate value. This is why a secure element matters and why the chips used in wallets are evaluated against exactly these techniques, with countermeasures such as constant-time operations, randomised execution and internal sensors that halt on tampering. Two things follow for an owner: the attack needs physical possession, which puts it behind the ordinary defences of not losing the device and not buying one second-hand, and no chip resists it forever.