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Security Fundamentals & Crypto · Advanced

Authenticated Encryption with Associated Data (AEAD)

Encryption that provides confidentiality, integrity, and authenticity, while also authenticating unencrypted header data.

Definition

AEAD algorithms output ciphertext plus an authentication tag that covers the ciphertext and any associated data, such as packet headers. Decryption fails if anything was modified. AES-GCM, AES-CCM, and ChaCha20-Poly1305 are the standard AEAD constructions, and TLS 1.3 requires AEAD.

Example

In TLS 1.3, the record header is associated data that is authenticated but not encrypted.

Exam tip

AEAD replaces older encrypt-then-MAC designs and avoids padding oracle issues.

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