Trézor Bridge®

Executive summary

Trézor Bridge® is a small trusted application that runs on a user's computer to facilitate safe, consistent communication between Trezor hardware wallets and web-based interfaces. It resolves cross-platform USB/HID inconsistencies, exposes an origin-bound, local API to browsers, and ensures that the cryptographic signing model remains device-centric: private keys never leave the hardware. Bridge is a pragmatic solution for web wallet integrations, developer tooling, and everyday users who want web convenience without compromising the security guarantees of an external signer.

Why Bridge?

Modern web browsers intentionally restrict direct hardware access for security reasons. Without a local intermediary, connecting web pages to hardware devices is brittle and platform-dependent. Bridge provides a stable, auditable, and permissioned local endpoint so that web applications can request public keys, propose transactions, and prompt for signatures — all while preserving physical, on-device confirmation as the final authority.

How Bridge preserves security

• Device-centric signing: All sensitive cryptographic operations (seed generation, key derivation, signing) occur on the Trezor hardware device.
• Origin-restricted access: Bridge implements strict origin checks so only permitted web origins can call the local API once explicitly allowed by the user.
• Explicit user consent: Bridge surfaces prompts for connection and relies on the browser's permission UX to avoid silent access by malicious pages.
• On-device verification: Devices display human-readable transaction details (addresses, amounts, tokens) so users can verify exactly what they sign.
• Verified updates: Bridge participates in signed firmware update flows; users are prompted to verify fingerprint hashes shown on-device during upgrades.

Key capabilities

• Cross-platform USB/HID handling for Windows, macOS and Linux.
• Local, loopback API with strict origin checks and scoped permissions.
• Automatic detection of connected Trezor devices, with route-to-instance handling for multiple devices.
• Developer libraries and examples (e.g., Trezor Connect) that illustrate how to call Bridge safely.
• CLI debugging flags, logging options, and status endpoints for power users and integrators.

Install, verify and run

Only download Bridge from the official Trezor website or verified package repositories. Verify installer checksums and digital signatures when available. After installation:

1. Start the Bridge application; it typically runs in the background and listens on a protected local endpoint.
2. When a trusted web application requests device access, Bridge will prompt to allow the origin. Confirm only for sites you trust.
3. Connect your hardware device using an official cable. Unlock the device if required and follow on-device prompts for firmware and actions.

Developer integration (illustrative)

Developers should use the official SDKs such as Trezor Connect. The snippet below is illustrative and not a production copy — always rely on the official, versioned libraries and their documentation.

// Illustrative example using Trezor Connect (simplified)
import TrezorConnect from 'trezor-connect';

async function init() {
  await TrezorConnect.init({
    manifest: { email: 'dev@yourapp.example', appUrl: 'https://yourapp.example' }
  });
}

async function getBtcAddress() {
  const res = await TrezorConnect.getAddress({ path: "m/44'/0'/0'/0/0", coin: 'BTC' });
  if (res.success) {
    console.log('Address:', res.payload.address);
  } else {
    console.error('Error', res.payload.error);
  }
}

Transaction lifecycle — browser + Bridge + device

1. Web app constructs an unsigned transaction proposal and requests the device via Bridge.
2. Bridge verifies origin permissions and forwards the proposal to the connected device over USB/HID.
3. Device parses the payload, displays readable fields (destination address, amount, fees, contract data), and asks the user to confirm.
4. Only after physical confirmation does the device generate the signature and return it via Bridge to the web app for broadcast.

Troubleshooting common issues

• Browser cannot find Bridge: Confirm Bridge is running and listening on the expected local port. Restart Bridge and the browser. Check firewall rules that might block localhost access.
• Permission denied: Revoke and re-grant the origin permission in the browser or bridge permission dialog. Only accept permissions for trusted sites.
• Device not detected: Try a different USB cable or port, ensure the device is unlocked, and check for conflicting drivers or other software that may claim the USB interface.
• Firmware update interrupted: Do not power off during an update. If an update fails, follow vendor-recommended recovery steps and consult official support channels.

Privacy considerations

Bridge is a local intermediary — it does not exfiltrate private keys or seed material. However, connected web apps may query block explorers or third-party APIs, which can leak metadata (addresses, txids, IP interactions). Review privacy policies of web apps you use and consider network-level protections if you need enhanced privacy. Local logs and debug traces may contain device or transaction metadata; keep them secure and avoid sharing with untrusted parties.

Security best practices for users

• Only install Bridge on systems you control and maintain with security updates.
• Allow connections only to trusted web origins and periodically review granted permissions.
• Always verify transaction details on the physical device display — do not rely solely on the web UI.
• Keep Bridge and device firmware updated using verified installers and fingerprint checks.
• For high-value operations, prefer air-gapped workflows or multisig arrangements where practical.

Enterprise & automation guidance

Enterprises integrating Bridge at scale should treat the host machine as part of the security boundary. Use hardened OS images, restricted network policies, and audited deployment tools. For automated signing, design policies requiring human-in-the-loop approvals for sensitive actions, or adopt multisig and HSM architectures instead of single-device signing. Maintain logs for audits but redact sensitive information and rotate credentials regularly.

CLI & diagnostics (examples)

# Illustrative commands — replace with vendor-provided tooling
trezor-bridge --status         # show running status
trezor-bridge --log-level debug # run Bridge with verbose logs
trezor-bridge --reinstall      # reinstall or repair installation (platform specific)

Compatibility and supported platforms

Legal & trademark note

Trézor and Trézor Bridge are registered product trademarks. This document is informational and should not be construed as legal advice. Observe licensing and trademark usage rules when building integrations or distributing derivative work. Always consult official documentation for the most current licensing terms.

Conclusion

Trézor Bridge® fills an important role in the hardware wallet ecosystem: it provides reliable, secure connectivity between modern web apps and offline private key material held on device. By enforcing origin checks, preserving on-device verification, and providing developer tooling, Bridge enables a wide range of web-based workflows while maintaining strong security guarantees. Install from official sources, verify updates, and always confirm operations on your hardware device to keep custody safe.

Quick checklist: Download from the official site • Verify installer checksums/signatures • Allow only trusted origins • Confirm transactions on-device • Keep software & firmware updated.