Differential power analysis (DPA) is a side-channel attack that recovers AES encryption keys by analyzing thousands of power traces captured with an oscilloscope. By controlling plaintext inputs, recording power consumption during AES128-ECB encryption, and statistically correlating power fluctuations with the output of the first-round S-box lookup, an attacker can guess each of the 16 key bytes independently (256 guesses each) rather than brute-forcing 2^128 combinations. A live demo using a ChipWhisperer-Nano recovered a full 16-byte AES key in about six minutes. Countermeasures include inserting random delays into the AES routine, adding noise via concurrent peripheral activity, and using side-channel-resistant AES implementations.
