Authentication Mechanisms (2FA, Hardware Tokens)

Authentication is a critical component of Anon VPN’s security model. While VPNs traditionally rely on simple username-password pairs for access control, Anon VPN employs a multi-layered authentication framework to strengthen identity verification and reduce the risk of credential-based attacks.

1. Authentication Layer Overview

Anon VPN separates authentication into three layers:

Layer	Function
Credential Layer	Validates initial identity (username, password, token)
Session Layer	Issues ephemeral session tokens post-authentication
Tunnel Layer	Establishes VPN tunnel using a validated session key

Each layer performs cryptographic validation before proceeding to the next, ensuring end-to-end identity assurance.

2. Username + Password (Base Layer)

This serves as the foundational credential mechanism, validated over secure TLS 1.3 connections with HMAC protections.

• Password Hashing: Anon VPN uses argon2id or bcrypt (configurable) with salt and pepper.

• Rate Limiting: Server-side throttling and exponential backoff reduce brute-force risk.

• Vault Storage: Credentials are stored in encrypted vaults with hardware-backed encryption (TPM, HSM).

3. Two-Factor Authentication (2FA)

TOTP-Based 2FA

Anon VPN supports Time-Based One-Time Passwords (TOTP) compliant with RFC 6238.

• Apps Supported: Google Authenticator, Authy, 1Password, etc.

• Token window skew: ±1 interval (configurable)

• Secret keys are stored encrypted and derived using PBKDF2

Setup Flow:

1. User enrolls via QR code.

2. Secret key is hashed and stored with optional biometric lock.

3. Login requires OTP + password combination.

TOTP verification is executed server-side using stateless validation logic to avoid replay attacks.

4. Push-Based Authentication (Planned)

• Integration with services like Duo, Okta, and PushID

• Challenge-response model using device-linked authentication

Example Flow:

Client → Login Request
Server → Sends push challenge to device
Device → User taps "Approve"
Server → Grants session token

5. Hardware Token Support

YubiKey (U2F / FIDO2)

Anon VPN supports Universal 2nd Factor (U2F) and FIDO2/WebAuthn for passwordless or 2FA-based authentication.

Key Capabilities:

Feature	Description
Public Key Auth	Challenge-response via stored key pairs
USB / NFC / BLE	Device versatility for all platforms
No Shared Secrets	Cryptographically signed challenge ensures no key leakage
Replay Resistance	Dynamic counters prevent cloned token abuse

Integration Details:

• Relies on browser support and JS libraries for initial handshake

• Token registration binds a unique key handle to user profile

• Authentication requires token insertion and user touch event

All authentication tokens are verified using cryptographic attestation from the YubiKey hardware.

6. Certificate-Based Authentication

Anon VPN supports X.509 certificate-based authentication for developers, enterprise clients, and self-hosted node operators.

Features:

• TLS mutual authentication using client certificates

• Configurable CA trust anchors

• Short-lived certificates to enforce key rotation and revocation

Use Case:

openvpn --config client.conf \
        --cert user.crt \
        --key user.key \
        --ca anon-root-ca.pem

7. Secure Enclave Integration (Planned)

TPM & Secure Enclave (macOS, iOS, Android Keystore)

• Leverages hardware-backed key stores for credential protection

• No private key ever leaves secure element

• Ideal for mobile devices and zero-trust environments

Future support includes:

• Windows Hello / TPM-backed credential store

• Android StrongBox-backed key signing

• Apple Secure Enclave + FaceID pairing

8. Biometric Authentication (Planned)

While not directly securing VPN tunnels, biometric factors are integrated at the client UI level for:

• App unlocking

• 2FA override

• Device fingerprinting

Supported methods will include:

• FaceID / TouchID

• Windows Hello (biometric fallback)

• Android BiometricPrompt API

Biometric data is never transmitted; authentication decisions are delegated to device hardware for compliance with GDPR and CCPA.

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9. Authentication Flow Example

sequenceDiagram
    participant U as User
    participant C as Client App
    participant S as Anon Auth Server

    U->>C: Enter credentials + TOTP
    C->>S: Send hashed credentials + OTP
    S->>S: Verify credentials, OTP
    S->>C: Return session token
    C->>S: Establish VPN handshake with session token
    S->>U: Secure tunnel established

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10. Security Practices

• Replay Protection: OTPs are one-time use only with strict time window enforcement.

• Device Fingerprinting: Prevents stolen token reuse from unauthorized devices.

• Secure Session Tokens: Authenticated using HMAC-SHA-512 with TTL enforcement.

• Session Timeout: Idle or expired sessions are invalidated automatically.

Summary

Anon VPN's authentication mechanisms are designed for both usability and cryptographic assurance. With support for modern 2FA, hardware-based identity validation, and a roadmap that includes biometric and enclave security, the platform provides robust, multi-modal identity protection suited for both individual users and enterprise deployments.