Skip to main content

​
Overview

Quantum-resistant tunnels add an additional layer of encryption to WireGuard connections using post-quantum cryptography. This protects your VPN traffic from potential future attacks by quantum computers that could break current encryption algorithms. Mullvad implements quantum resistance through ephemeral pre-shared keys (PSK) negotiated using post-quantum key encapsulation mechanisms (KEM).
Quantum-resistant tunnels are available on all platforms: Windows, Linux, macOS, Android, and iOS.

​
How It Works

​
Traditional WireGuard Encryption

Standard WireGuard uses:
  • Curve25519: Elliptic curve cryptography for key exchange
  • ChaCha20-Poly1305: Symmetric encryption
These algorithms are secure today but could potentially be broken by quantum computers in the future.

​
Quantum-Resistant Enhancement

Mullvad adds a quantum-resistant layer:
  1. Post-Quantum KEM: Generates ephemeral key pairs using post-quantum algorithms
  2. PSK Exchange: Securely negotiates a pre-shared key with the relay server
  3. WireGuard PSK: The negotiated key is used as WireGuard’s pre-shared key field
  4. Hybrid Security: Combined classical (Curve25519) + post-quantum cryptography
┌─────────────────────────────────────────────────────┐
│   Application Data (Your Internet Traffic)          │
└─────────────────────────────────────────────────────┘
                      │
                      ▼
┌─────────────────────────────────────────────────────┐
│   WireGuard Encryption (ChaCha20-Poly1305)          │
│   + Pre-Shared Key (Post-Quantum)                   │
└─────────────────────────────────────────────────────┘
                      │
                      ▼
┌─────────────────────────────────────────────────────┐
│   Curve25519 Key Exchange (Classical)               │
└─────────────────────────────────────────────────────┘
This “hybrid” approach provides security even if either the classical or post-quantum algorithm is compromised.

​
Key Exchange Process

​
Ephemeral PSK Negotiation

The PSK is never persisted to disk and is regenerated for each tunnel:
  1. Key Generation: Client generates post-quantum KEM key pairs
  2. Request: Client sends public key to relay server via TLS 1.3
  3. Encapsulation: Server generates shared secret and encapsulates it
  4. Response: Server returns encapsulated secret
  5. Decapsulation: Client decapsulates to derive shared secret
  6. PSK Derivation: Shared secret becomes WireGuard PSK
The PSK is stored in memory only and is never written to disk. It’s automatically zeroized when the tunnel is torn down.

​
Enabling Quantum-Resistant Tunnels

​
Using the GUI

1

Open Settings

Launch Mullvad VPN and navigate to Settings → VPN settings
2

Enable Quantum Resistance

Find the Quantum-resistant tunnel option and toggle it On
3

Reconnect

The app will automatically reconnect with quantum-resistant encryption enabled

​
Using the CLI

# Enable quantum-resistant tunnels
mullvad relay set tunnel wireguard quantum-resistant on

# Disable quantum-resistant tunnels
mullvad relay set tunnel wireguard quantum-resistant off

# Check current setting
mullvad relay get

​
Verify It’s Active

When connected with quantum resistance enabled: 
mullvad status -v
You should see: 
Connected to ...
Quantum resistant: yes
The connection panel in the GUI will also display a quantum resistance indicator.

​
Performance Impact

​
Connection Establishment

  • Slight increase in connection time: Additional PSK negotiation adds ~100-200ms
  • Key generation: Post-quantum key pair generation takes a few milliseconds

​
Ongoing Connection

  • No throughput impact: Once established, performance is identical to standard WireGuard
  • No additional CPU overhead: PSK is used in existing WireGuard encryption
The performance impact is minimal and only affects the initial connection. Once connected, there’s no difference in speed or bandwidth.

​
Security Properties

​
Threat Model

Quantum-resistant tunnels protect against:
  • Store-now-decrypt-later attacks: Adversaries recording encrypted traffic today to decrypt with future quantum computers
  • Future quantum cryptanalysis: Breaks in classical ECC algorithms

​
Cryptographic Algorithms

Mullvad uses NIST-approved post-quantum algorithms for KEM:
  • Post-quantum key encapsulation mechanisms
  • Hybrid construction combining classical and post-quantum security

​
Limitations

Does not protect against:
  • Traffic analysis (see DAITA)
  • Correlation attacks on VPN servers
  • Compromise of the Mullvad service itself
  • Local device compromise

​
Compatibility with Other Features

Quantum-resistant tunnels work with:

​
Example: Quantum-Resistant Multihop

# Enable quantum resistance with multihop
mullvad relay set tunnel wireguard quantum-resistant on
mullvad relay set tunnel wireguard use-multihop on

​
Technical Details

​
PSK Storage

From the source code (talpid-types/src/net/wireguard.rs:295-306): 
/// A WireGuard preshared key (PSK). Used to make the tunnel quantum-resistant.
#[derive(Clone, PartialEq, Eq, Hash, Zeroize, ZeroizeOnDrop)]
pub struct PresharedKey(Box<[u8; 32]>);
  • PSK is 32 bytes (256 bits)
  • Automatically zeroized on drop (secure memory cleanup)
  • Never serialized or deserialized to disk

​
Key Rotation

PSKs are ephemeral:
  • New PSK negotiated for each tunnel connection
  • PSK is discarded when tunnel disconnects
  • No persistent key storage

​
Troubleshooting

​
Connection Failures

If quantum-resistant connections fail:
  1. Check server support: Ensure selected relay supports quantum resistance
  2. Network connectivity: PSK exchange requires API connectivity
  3. Firewall rules: Ensure HTTPS (443) to Mullvad API is allowed
  4. Temporary disable: Try disabling quantum resistance to isolate the issue

​
Verification

# Check if quantum resistance is active
mullvad status -v | grep -i quantum

# View tunnel configuration
mullvad relay get

​
Migration from Legacy Settings

Older Mullvad versions used use_pq_safe_psk setting:
  • Automatically migrated to quantum_resistant in newer versions
  • auto setting means enabled by default
  • Settings persist across app updates

​
Best Practices

Enable all quantum-resistant features:
mullvad relay set tunnel wireguard quantum-resistant on
mullvad relay set tunnel wireguard use-multihop on
mullvad tunnel set tunnel wireguard daita on

​
Further Reading

Build docs developers (and LLMs) love

Get started for freeTalk to us