# Authentication Policy (Comprehensive, EU‑Aligned)

**Document owner:** [Owner/Role]  
**Approved by:** [Steering Committee / CISO]  
**Effective date:** [YYYY-MM-DD]  
**Review cadence:** [Annually]

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## 1. Purpose & Scope
This policy establishes mandatory requirements for authentication across [Organization] systems, including:  
- Passwords and memorized secrets  
- Multi‑factor authentication (MFA)  
- Authenticator Assurance Levels (AALs)  
- Out‑of‑band (OOB) authentication  
- Central vs. local authentication  
- Special cases (BitLocker, local admin accounts, device/smart‑card/mobile PINs)  
- Session management and reauthentication  

It is aligned with **NIST SP 800‑63B** (as best practice), **CIS Controls v8.1**, and **ENISA guidance**.  
It applies to all employees, contractors, vendors, and service accounts.  
This policy supports GDPR principles of **data protection by design** and **accountability**.

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## 2. Policy Statements

### 2.1 Assurance Levels
- [Organization] **shall** align with Authenticator Assurance Levels (AALs):  
  - **AAL1:** Single‑factor authentication. Permitted only for low‑sensitivity internal apps or offline scenarios.  
  - **AAL2:** Multi‑factor authentication combining two categories (e.g., password + OTP app, push, QR code OOB). Required for employee logins, SaaS, and external‑facing systems.  
  - **AAL3:** High‑assurance, hardware‑backed MFA (e.g., FIDO2, smartcards). Required for privileged/admin access, production, and regulated data systems.  

### 2.2 Memorized Secrets (Passwords)
- **Length:**  
  - **15+ characters** when used as a single factor.  
  - **8+ characters** when used only in combination with MFA.  
  - Systems **must** allow at least **64 characters**, accept **spaces/Unicode**, and **must not truncate** entered secrets.  
- **Composition:** No mandatory composition rules (no required mixes of upper/lower/digit/symbol).  
- **Screening:** New/changed passwords **must** be screened against **blocklists** of commonly used, expected, or **compromised** passwords (including organization‑specific terms).  
- **Expiration:** **No periodic expiration**. Change **only** upon suspected compromise or policy breach.  
- **Usability:** **Allow paste/autofill** and provide a **“show password”** option. **No password hints** and **no knowledge‑based questions (KBA)**.  
- **Reuse:** Password **must not** match the user’s current or any **of the last 5** passwords (where technically supported).  
- **Rate limiting:** Verifiers **must** throttle online guessing (progressive delays; avoid permanent lockout DoS).  
- **Storage:** Store only **salted, hashed** verifiers using **Argon2id (preferred)**, **bcrypt**, or **PBKDF2** with strong parameters; per‑credential unique salt; optional server‑side **pepper** protected separately.  
- **Transport:** Collect and transmit passwords only over **authenticated, encrypted channels** (TLS 1.2+).  
- **Managers:** Users **should** use an approved **password manager** to generate/store unique passwords.  

### 2.3 Activation Secrets (Local Unlock PINs/Biometrics)
- **Definition:** An **activation secret** (e.g., device PIN, Windows Hello PIN, smart‑card PIN, FIDO2 PIN) is used **only to unlock a local authenticator/TPM/smart‑card**. It is **not transmitted** to a server and is **not** a password.  
- **Requirements:** Activation secrets **shall** remain on the device/token; **shall be ≥4 characters** and **should be ≥6**; online guesses **shall** be throttled/limited locally.  
- **Biometrics:** May be used **only** to unlock a device‑bound key and **must not** be the sole authenticator.  

### 2.4 Acceptable Authenticators
- **Allowed:** FIDO2/WebAuthn keys; smartcards with PIN; authenticator apps (TOTP, push, **QR‑code sign‑in**); device‑bound biometrics (unlock only).  
- **Fallback only:** SMS/voice OTPs.  
- **Prohibited:** Email OTP; KBA/security questions.  

### 2.5 Out‑of‑Band (OOB) Methods
- OOB authenticators **must** use **encrypted, device‑bound** channels (e.g., push or QR‑code flows) and **must** implement rate‑limiting.  
- **SMS/voice/email** **must not** be used as **primary** MFA. SMS/voice may be used **only** as recovery with risk acceptance.  

### 2.6 Central vs. Local Authentication
- **Central IdP/SSO** **must** be the default for enterprise access.  
- **Local authentication** (device‑only) may be used for **pre‑boot**, **offline**, or **recovery**, but **must** meet the applicable AAL and other requirements in this policy.  

### 2.7 BitLocker Pre‑Boot Authentication
- **TPM only:** AAL1; not acceptable for sensitive systems.  
- **PIN only (no TPM):** AAL1; acceptable only with compensating controls.  
- **TPM + PIN:** AAL2; recommended baseline for enterprise laptops.  
- **TPM + PIN + post‑boot FIDO2/smart‑card MFA:** Meets AAL3 for administrative systems.  

### 2.8 Local Administrator Accounts
- Local admin accounts **must not** share passwords across devices.  
- **LAPS or equivalent** **must** randomize and rotate local admin passwords.  
- Local admin accounts **must not** be used for daily administration; use **central privileged accounts with MFA** (AAL2/AAL3).  

### 2.9 Reauthentication & Session Management
- **AAL1:** Reauthentication **≤ 30 days**.  
- **AAL2:** Reauthentication **≤ 24 hours**, inactivity timeout **≤ 1 hour**.  
- **AAL3:** Reauthentication **≤ 12 hours**, inactivity timeout **≤ 15 minutes**.  

### 2.10 Enforcement
- Violations **may** result in disciplinary action or revocation of access.  
- Non‑compliant systems **must** be remediated or formally excepted with CISO approval.  

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## 3. References
- NIST SP 800‑63B (Digital Identity Guidelines, 2023 update)  
- CIS Controls v8.1 (Controls 5 & 6)  
- ENISA Guidelines on Identity and Access Management  
- OWASP Authentication Cheat Sheet