Side-channel attacks

A side-channel attack extracts secrets from a hardware wallet by observing its physical behavior instead of breaking cryptographic math. The attacker watches leaks such as power use, electromagnetic emissions, timing differences, or tiny sounds. These leaks form fingerprints that depend on the processed data. Simple power analysis reveals patterns directly from raw traces. Differential power analysis uses statistics across many traces to amplify tiny differences. An attacker first needs physical access to the device long enough to instrument it. They may open the case and attach probes to the circuit board or use nearby antennas to capture emissions. The attacker then feeds many known inputs like PIN guesses while recording traces. Each recorded trace is labeled with the attempted input value to build a template database. Statistical methods such as correlation or hypothesis testing match unknown traces against the templates. Repeating this for each digit lets the attacker recover a PIN one digit at a time. The same approach works on processing steps for keys or signatures if the implementation leaks. Such attacks do not target the math of cryptography. They abuse the implementation and the device body. The device sits at the border between silence and leakage, and small physical differences reveal internal states. Successful attacks often require lab gear like oscilloscopes and experience in signal processing. However, remote variants exist for timing and network-based leaks. Defenses operate at hardware and software layers. Hardware countermeasures include shielding, power filtering, and secure elements that isolate secrets. Software defenses include constant-time algorithms, masking, random delays, and limiting observable variations during sensitive operations. System-level protections include retry limits, tamper sensors, secure boot, and requirement of user confirmation for critical actions. Users reduce risk by keeping devices physically secure, applying firmware updates, enabling retry locks, and adding passphrases on top of PINs. Researchers use responsible disclosure to push vendors to fix flaws and to design products with side-channel resistance in mind. Side-channel attacks are a mature field that shows how physical realities can bypass idealized security, and understanding them helps both builders and users close the gap between theory and the vulnerable hardware that carries our keys.