side-channel

**Side-Channel Attack Countermeasures** is **a collection of design and implementation techniques mitigating information leakage through physical channels including power consumption, timing, and electromagnetic emissions** — Side-channel attacks exploit implementation vulnerabilities enabling attackers to extract secret keys without algorithmic cryptographic breaking. **Power Analysis** attacks extract keys by correlating power consumption with cryptographic operations, including simple power analysis (SPA) observing power waveforms, differential power analysis (DPA) correlating power with data, and correlation power analysis (CPA) applying statistical techniques. **Countermeasures** include power randomization injecting random values into computations, dummy operations eliminating operation-dependent power variations, and voltage regulation smoothing power supply fluctuations. **Timing Attacks** exploit algorithm execution time variations dependent on processed data, particularly vulnerable in variable-time algorithms with data-dependent branches. **Timing Defenses** implement constant-time algorithms executing identical operations regardless of inputs, include dummy operations balancing true and false branches, and randomize execution sequences eliminating timing correlations. **Electromagnetic Analysis** observes radiation emitted from switching transistors, enabling non-contact key recovery from shielded devices. **EMI Countermeasures** include metal shielding reducing emission, spread-spectrum clocking decorrelating emissions from data, and random routing reducing emission patterns. **Fault Injection** exploits induced errors revealing cryptographic state, requiring detection circuits, error correction, and algorithm robustness against faults. **Side-Channel Attack Countermeasures** demand holistic approaches addressing multiple physical leakage mechanisms simultaneously.