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Security Fundamentals & Crypto · Advanced

Authenticator Assurance Level (AAL)

NIST SP 800-63B rating (AAL1-AAL3) of confidence that the person authenticating controls the account's authenticators.

Definition

AAL1 allows single-factor authentication; AAL2 requires two factors with approved methods; AAL3 requires a hardware-based, phishing-resistant cryptographic authenticator with verifier impersonation resistance. SP 800-63 also defines IAL for proofing and FAL for federation assertions.

Example

A federal system holding sensitive health data requires AAL3 with PIV or FIDO2 hardware keys.

Exam tip

IAL = proofing, AAL = authentication, FAL = federation.

Related terms