> ## Documentation Index
> Fetch the complete documentation index at: https://docs.zerokeyusb.com/llms.txt
> Use this file to discover all available pages before exploring further.

# NIST SP 800-63B alignment

> How ZeroKeyUSB aligns with NIST SP 800-63B guidance on authentication secrets and their protection — an alignment statement, not an Authenticator Assurance Level certification.

<Note>
  **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.
</Note>

## 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](/compliance/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.