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Security Fundamentals & Crypto · Intermediate

Entropy

Measure of randomness or unpredictability, critical for generating strong keys and passwords.

Definition

Cryptographic keys, nonces, and salts require high-entropy random sources. Low entropy, such as at early boot on embedded devices, has caused weak duplicate keys in the wild. Password entropy estimates guessing difficulty in bits.

Example

Research found many embedded devices sharing RSA factors because of low entropy at key generation.

Exam tip

Weak randomness undermines strong algorithms; questions may cite low entropy as a root cause.

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