This presentation explains Trezor Bridge, its role in secure device communication, and best practices for developers and users. We'll cover architecture, threat model, secure update patterns, platform compatibility, and practical recommendations to keep keys safe while ensuring a seamless UX.
Trezor Bridge is a small, trusted background application that facilitates communication between a Trezor hardware wallet and web or desktop clients. It abstracts USB and WebUSB complexities and provides a consistent transport layer so wallets and apps can exchange messages securely without requiring low-level device drivers.
Communication flows: User app ➜ Bridge (local agent) ➜ Trezor device. The Bridge proxies JSON-RPC or APDU payloads to the device and returns signed responses. It handles transport negotiation, versioning, and secure update checks, ensuring the device speaks a known protocol and the host application only gets minimal, expected data.
The security model assumes the host OS may be compromised at user-level, but the Trezor device remains the root of trust. Bridge reduces risk by limiting data exposure, requiring explicit user confirmations on-device for sensitive operations, and verifying firmware authenticity for updates. The most important guarantee: private keys never leave the device.
Bridge uses explicit connection flows: the web client requests access, the Bridge prompts the user via OS UI or device confirmation, and the user approves. Good UX patterns include clear device naming, informative prompts on the device's screen, and minimizing repeated prompts while maintaining per-origin or per-client authorization.
Always review the device prompt text before confirming — on-device confirmation is the strongest protection against hostile hosts.
Updates must be signed and verified. Bridge checks digital signatures for firmware images and updates itself through authenticated channels. Ensure update mechanisms use strong cryptographic signatures and display clear verification status to users. Avoid automatic silent firmware upgrades without user consent.
When building apps, do not bypass update checks or signature validations — these preserve the chain of trust between vendor and device.
Bridge is designed to work across major desktop OSes. Web clients can use WebUSB when available or fallback to Bridge protocol. Important compatibility decisions include signed installer packages for macOS/Windows and distribution channels that ensure users install a genuine Bridge binary.
Use the Bridge API correctly: verify device responses, avoid sending unnecessary sensitive data, and implement origin checks in the client. Encourage users to verify transaction details on the device screen, and add logging for connection and error states without storing sensitive payloads.
Operational security includes educating users about genuine download sources, phishing risks, and physical device safety. Offer guides for verifying Bridge versions and firmware signatures, and provide clear recovery procedures if a device is lost or compromised.
Provide users with step-by-step recovery documentation and clear channels for reporting suspicious downloads or activity.
Trezor Bridge serves as a trusted transport layer that simplifies communication between apps and the hardware wallet while preserving security guarantees. Core principles: keep private keys on-device, use signed updates, require on-device confirmations, and educate users. For developers: follow the integration checklist, and for users: only install Bridge from trusted sources.