Alignment, not accreditation. NIST SP 800-63B specifies requirements for
authenticators in a federal digital-identity context and defines Authenticator
Assurance Levels (AAL). ZeroKeyUSB is a credential store, not an accredited
authenticator, and makes no AAL claim. This page shows how it helps
subscribers and organizations follow 800-63B’s good practices.
Where ZeroKeyUSB helps
| 800-63B theme | Guidance (paraphrased) | How ZeroKeyUSB supports it |
|---|---|---|
| Strong secrets | Encourage long, high-entropy secrets; do not force composition rules that weaken them | Generates up to 32-character passwords from a hardware TRNG; supports memorable multi-word passphrases |
| No reuse | Discourage reuse across services | Each stored credential is independent; unique random passwords are one tap away |
| Secret storage | Verifiers must store secrets protected (hashed/encrypted), not in the clear | Credentials are AES-encrypted off-host; the Master PIN is stored only as SHA-256(PIN ‖ serial) — never in the clear |
| Rate limiting | Limit failed authentication attempts to resist online guessing | Persistent exponential backoff on the PIN, re-applied on every boot so it cannot be reset by power-cycling |
| Verifier compromise resistance | Reduce impact of a compromised endpoint | Credentials never reside on the host and the AES key never leaves the secure element |
| Memorized-secret handling | Salt and hash memorized secrets; compare safely | The PIN uses the device serial as salt and a constant-time comparison |
Honest gaps versus a formal 800-63B authenticator
- ZeroKeyUSB is not a phishing-resistant cryptographic authenticator (e.g. a FIDO2 key); it types passwords, which are a “memorized secret / look-up secret” style factor.
- It does not perform online proof-of-possession with a relying party; it augments password-based auth rather than replacing it.
- The PIN hash is single-pass
SHA-256(not a heavy KDF) and is readable over I²C, so its offline-resistance depends on the physical encapsulation and PIN length — see the Threat model.
Suggested statement
ZeroKeyUSB’s design aligns with NIST SP 800-63B guidance on strong, unique authentication secrets, protected secret storage and rate-limited verification. It is a credential-protection device, not an accredited authenticator, and makes no Authenticator Assurance Level claim.