What Happens During a Firmware Update in Trezor Suite

A visually guided, sectioned explanation — secure, step-by-step, and developer-friendly.

1. Starting the Update — User Intent & Safety Check

What triggers the process

When you click Update firmware in Trezor Suite, the app first confirms your intent and checks that the connected hardware (your Trezor device) is genuine and responsive. This reduces accidental updates and prevents man-in-the-middle operations.

Highlight: Trezor Suite refuses to auto-install unknown firmware — user confirmation is mandatory.
Tip: Always ensure your device is plugged directly into your computer (avoid hubs) and has stable power.

2. Version Check & Compatibility

Which firmware and why

The Suite queries the official Trezor firmware server to fetch metadata: the latest version number, supported device models (Trezor One, Trezor Model T), and the cryptographic hash/signature that will later be used to verify authenticity.

  • Compares installed vs available firmware version
  • Checks device compatibility (hardware model & bootloader)
  • Displays release notes and changelog

3. Pre-flight Backup Reminder

Safety first

Trezor Suite reminds you to confirm your recovery seed is backed up. The update typically doesn't erase the seed, but power loss or an interrupted flash could leave the device temporarily unusable until restored.

Pro tip: Treat your seed like the master key — ensure it's stored offline and verifiable before updating.

4. Cryptographic Verification

Ensuring the firmware is legitimate

Before transferring any binary to the device, Suite validates the firmware package using digital signatures. This uses public-key cryptography: the Suite checks that the firmware was signed by Trezor's official private key and that the signature matches the embedded public key or server-provided key.

Security note: Even if the package is intercepted in transit, a bad signature will stop the update.

5. Establishing a Secure Channel

How the computer and device communicate

Trezor Suite and the device establish an encrypted and authenticated channel for the firmware transfer. The device might switch to a bootloader mode — a minimal, trusted program designed solely for firmware flashing — which only accepts signed firmware.

Key point: Bootloader mode reduces the risk of corrupting the main application code during transfer.

6. Chunked Download & Transfer

Safe, resumable transfer

The firmware binary is sent in small chunks to the device. Chunking keeps memory usage low and allows verification at multiple stages. Each chunk is acknowledged by the device; failed transmissions trigger retries rather than blind continuation.

  • Reduces the risk of bricking from a single failed packet
  • Enables progress feedback and integrity checks

7. Integrity Checks During Transfer

Checksums and hashes

After some or all chunks are received, the device computes a hash (e.g., SHA-256) of the assembled firmware and compares it to the expected hash sent with the package. If they differ, the firmware is rejected and the device remains in a safe state.

Why this matters: It prevents silent corruption caused by hardware issues or malware-altered files.

8. Flashing / Writing to Memory

Replacing the code that runs on the device

When the device is satisfied the firmware is authentic and intact, the bootloader writes the new image into flash memory. This often involves erasing previous sections safely and writing new sectors while preserving critical configuration and seed storage partitions.

Design detail: Secure bootloaders write to isolated partitions so the recovery seed remains encrypted and untouched.

9. Atomic Swap or Dual-Bank Strategy

How devices avoid being left unusable

Many secure devices use an "atomic" update or dual-bank layout: the device keeps the old firmware until the new firmware is fully written and validated, then switches execution to the new bank. If anything fails, it can roll back to the old image.

Outcome: Less chance of a permanently bricked device after interrupted updates.

10. Post-flash Verification & Self-test

Ensuring the device boots correctly

After flashing, the device boots the new firmware and runs self-tests. It verifies core functions (display, buttons, crypto engine) and confirms that secrets are accessible and intact. Trezor Suite checks for expected firmware responses and notifies you that the update succeeded.

If tests fail, the device typically re-enters bootloader mode and presents recovery options.

11. User Confirmation & Finalization

You get the final say

Suite displays a final confirmation: success, new firmware version, and sometimes a checksum or safety token to verify later. The app may ask you to confirm basic operations (e.g., check address or sign a test message) to ensure everything behaves as expected.

Always validate an address or signature after an update if you plan to send funds immediately.

12. Recovery Mode & Rollback Procedures

What happens if things go wrong

If flashing fails, the device usually falls back to bootloader and allows reinstallation or rollback to the previous firmware. In the worst case, you can recover device access by re-flashing an official firmware using Suite or by restoring from your recovery seed on a fresh device.

Emergency tip: Having your seed accessible (offline) is the ultimate insurance policy.

13. Security Considerations & Attacks Mitigated

Threat model coverage

The Suite + device firmware update workflow defends against supply-chain tampering, network injection, and local MITM attacks by enforcing signatures, secure channels, and explicit user consent. It also reduces risk from partial writes with atomic updates.

  • Signature enforcement stops forged firmware
  • Bootloader isolation prevents unauthorized code execution
  • Chunking + verification prevents corruption

14. Common Troubleshooting Steps

If the update stalls or errors

Typical fixes include: reconnecting the cable, using a different USB port (prefer direct ports, not hubs), ensuring Suite is up to date, restarting your computer, or reattempting the update in bootloader mode. If problems persist, follow official recovery guides and reach out to Trezor support.

Do not attempt third-party firmware unless you fully understand the risks.

15. Privacy & Telemetry

What Suite may collect (high level)

Trezor Suite typically minimizes telemetry; firmware update checks may request only version metadata from the server and do not transmit your seed or private keys. The Suite may ask for optional diagnostics only with explicit consent.

Privacy-first: the update process is designed to avoid leaking account or seed information.

16. Final Notes & Best Practices

A checklist for smooth updates
  • Verify your recovery seed is secure before starting.
  • Use the official Trezor Suite application and firmware sources.
  • Keep a reliable power and cable connection for the duration.
  • Prefer direct USB ports over hubs or docking stations.
  • Confirm device functions post-update (view address/sign test).