Trezõr® brïdge®

Executive Summary

Trezõr® brïdge® acts as the trusted local gateway between web3 applications (including wallet interfaces) and your Trezor hardware wallet. It runs as a lightweight background service, exposing a secure localhost API that web apps and desktop clients can call. Bridge's role is strictly facilitative — translating web-level requests into USB/HID operations and relaying user-approved responses back to the application. The hardware device is the canonical place where signing and key operations occur; Bridge never extracts or stores private keys. This guide explains how Bridge works, how to install and verify it, how developers can integrate with it, the security model and threat mitigations, common troubleshooting steps, and best practices for safe real-world usage.

Why Bridge Exists

Browsers historically restricted direct access to USB devices for security and cross-platform consistency reasons. Bridge exists to provide a dependable, cross-browser, cross-platform mechanism to bridge that gap. By running a local service, Bridge offers broader compatibility, more predictable behavior, and a simpler user experience. Instead of relying on diverse browser APIs and their varying implementations, Bridge centralizes device communication while keeping operations safe and transparent.

How Bridge Works — A High-Level Flow

1. Launch: Bridge runs as a background service on the user’s machine, listening on a localhost port only accessible from the same device.
2. Request: A web3 app (web or desktop) sends a request to Bridge to access a connected Trezor device (list devices, sign payload, get public keys, etc.).
3. Forward: Bridge translates the web request into the device’s native protocol and forwards it via USB/HID.
4. User Confirm: The Trezor device displays details (addresses, amounts, contract data) and requires explicit physical confirmation via buttons.
5. Response: After confirmation, the device signs or performs the requested action; Bridge relays the result back to the application for broadcasting or display.

This split of responsibilities—UI and orchestration handled by apps, cryptography confined to the hardware—maintains a secure separation of duties and reduces attack surface.

Installing & Verifying Bridge

Installation is typically offered during the companion app setup or as a standalone installer for your operating system. Key steps to follow:

• Download only from official channels — do not use untrusted mirrors. Keep installation packages and installers from known, verified sources.
• Verify installers where possible using checksums or signatures. This is an advanced step but guards against tampered binaries.
• Run the installer with standard privileges and ensure the Bridge process is allowed to start on boot or when needed.
• Confirm Bridge is running by noting the local service or by attempting to access a supported web interface which will detect Bridge automatically.

If you prefer not to install Bridge, some modern browsers may offer direct device support via WebUSB/WebHID. However, Bridge remains the most consistent experience across varied platforms and browser versions.

Security Model & Guarantees

Bridge is built with the assumption that the host computer can be partially untrusted. It minimizes risk through design choices:

• Key confinement: Private keys and seed materials never leave the Trezor device. Bridge cannot access or export them.
• Device-first confirmation: All sensitive actions require the user to physically confirm on the Trezor device; the device display is the canonical source of truth.
• Localhost-only API: Bridge listens only on localhost to prevent remote network access; only local processes can communicate with it.
• Minimal surface area: Bridge implements a limited, focused API — fewer features mean fewer potential vulnerabilities.
• Origin checks & prompts: Where possible, Bridge and applications validate request origins and prompt the user when trust choices arise.

Despite robust protections, Bridge cannot fully eliminate risks from a compromised host. Threats like clipboard hijacking, screen overlays, or malicious applications can attempt to manipulate user intent. The recommended defense is always to verify critical transaction details on the Trezor device itself.

Developer Guide: Integrating with Bridge

Developers building web3 applications can integrate with Bridge to enable hardware wallet support. A minimal integration flow looks like this:

// 1) Detect Bridge by attempting a connection to localhost
// 2) Request device list
// 3) Send prepare-and-sign commands
// 4) Handle user confirmation and signed response

Example (pseudocode):

async function signTx(payload) {
  // 1. Ensure bridge is reachable (localhost:port)
  await bridge.connect();
  // 2. Request connected devices
  const devices = await bridge.listDevices();
  // 3. Prepare unsigned transaction payload
  const unsignedTx = buildTx(payload);
  // 4. Send signing request
  const signed = await bridge.signTransaction(devices[0].path, unsignedTx);
  // 5. Broadcast signed transaction
  return broadcast(signed);
}

Best practices for developers:

• Minimize the data sent to Bridge. Avoid requesting unnecessary sensitive details.
• Clearly display transaction metadata and require explicit user confirmation steps in the UI before requesting device signing.
• Handle user cancellations gracefully and do not retry automatically without user action.
• Implement robust error handling and provide clear troubleshooting instructions when Bridge or device access fails.
• Respect user privacy and avoid logging sensitive request contents.

Troubleshooting Common Issues

Real-World Use Cases

Bridge enables a variety of practical scenarios:

• DEX interactions: Signing contract interactions securely from your browser without exposing keys.
• Portfolio managers: Viewing and managing multiple accounts across chains while keeping signing on-device.
• Developers: Building tools that require hardware-backed signing for testnets and mainnets.
• Educational labs: Demonstrating secure signing flows to students and community members in workshops.

Best Practices for Users

• Install Bridge from official sources and keep it updated.
• Use trusted computers for large-value operations and avoid public devices.
• Always confirm transaction details on the Trezor device screen—device display is the single source of truth.
• Monitor for unexpected Bridge prompts and terminate the process if behavior seems unusual.
• Use hardware PINs and consider passphrase-protected hidden wallets only if you understand recovery tradeoffs.

Privacy Considerations

Bridge facilitates local communication and does not send private keys or seeds anywhere. However, note that metadata (such as which apps are using Bridge or timing of operations) can be observed on the host. To minimize exposure, avoid using Bridge on public machines and ensure your system is free from surveillance software. Review installed browser extensions and system monitoring tools that could leak local activity.

FAQ

• Q: Is Bridge safe?
  A: Yes — Bridge is designed as a secure local relay. Critical cryptographic operations remain on the Trezor device; Bridge only transports requests and responses locally.
• Q: Can I avoid installing Bridge?
  A: In some cases, yes — modern browsers may support direct WebUSB/WebHID. However, Bridge provides broad compatibility and a more consistent experience across platforms.
• Q: Can Bridge access my recovery seed?
  A: No — Bridge has no access to the recovery seed or private keys. Those are confined to the device.
• Q: What should I do if Bridge acts unexpectedly?
  A: Terminate the Bridge process, reinstall from an official source, and investigate system logs. If unsure, consult official support channels or reinstall your OS in extreme cases.

Closing Thoughts

Trezõr® brïdge® provides a practical, secure pathway for connecting hardware wallets to the vibrant web3 ecosystem. By limiting scope, enforcing device confirmations, and running locally, Bridge balances usability and security for everyday tasks and advanced integrations. Adopt the recommended best practices: install from trusted sources, verify important operations on your device, and use trusted machines for sensitive interactions. With those precautions, Bridge empowers you to interact with decentralized apps and services without compromising the core security guarantees of your hardware wallet.