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Security Fundamentals & Crypto · Foundational

Cryptographic Key

A secret or public value used by a cryptographic algorithm to transform data.

Definition

Keys control the output of encryption, decryption, signature, and MAC algorithms. Symmetric keys must be kept secret by all parties; in asymmetric cryptography, the private key is secret while the public key can be shared. The security of a cryptosystem depends on key secrecy, length, randomness, and management.

Example

A 256-bit AES key is a random 32-byte value generated by a CSPRNG or HSM.

Exam tip

Most real-world crypto failures are key management failures, not algorithm breaks.

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