Exploiting physical implementation weaknesses is characteristic of which attack?

• A. Side-channel attack
• B. Replay attack
• C. Downgrade attack
• D. Steganography

Answer: (A)

Side-channel attacks exploit physical implementation weaknesses by observing leakage that occurs during cryptographic operations, such as variations in power consumption, timing, or electromagnetic emissions. These side effects can reveal secret information like cryptographic keys because the way a computation is carried out on real hardware or software leaves measurable traces. For example, analyzing how much power a device uses during modular exponentiation can reveal bits of a private key, or timing differences can leak information about processed data.

This is different from other approaches: a replay attack relies on capturing and resending valid communications to deceive a system, a downgrade attack forces a protocol to use weaker security, and steganography hides data inside other media.