# CatCard: replacement firmware built around Coldcard bootloader contracts

> CatCard implements Rust replacement firmware for Coldcard mk3, mk4, mk5 and Q1 hardware. It documents the protected bootloader's image layout, signature and callgate ABI, then builds board-specific wallet, storage and USB components against those fixed interfaces. The author reports that device builds run, while signing and several transports remain without end-to-end device exercise.

- Type: Case study
- Targets: Firmware
- Category: Independent reconstruction cases
- Relationship: Independent reconstruction project
- Sources reviewed: 2026-11-08
- Added to the catalog: 2026-11-09
- Original resource: <https://github.com/TibaneLabs/catcard>
- Primary source: <https://github.com/TibaneLabs/catcard/blob/038c37cac7b906ed73452479147fe1bda97004ee/docs/ARCHITECTURE.md>
- Catalog page: <https://awesomerea.org/resources/catcard-coldcard-firmware-case/>
- Record JSON: <https://awesomerea.org/resources/catcard-coldcard-firmware-case/record.json>
- Chinese version: [简体中文](https://awesomerea.org/zh/resources/catcard-coldcard-firmware-case/index.md)

## Requirements & limits

- **Prerequisites:** Coldcard mk3, mk4, mk5 or Q1 hardware; firmware images use the bootloader's published developer signing key.
- **Testing evidence:** The author states the firmware is not ready to hold funds; signing, multisig, QR and NFC have not been exercised end to end on a device.
- **License:** MIT License.

## Primary sources

1. <https://github.com/TibaneLabs/catcard/blob/038c37cac7b906ed73452479147fe1bda97004ee/docs/ARCHITECTURE.md>
2. <https://github.com/TibaneLabs/catcard/blob/038c37cac7b906ed73452479147fe1bda97004ee/README.md>
3. <https://github.com/TibaneLabs/catcard/blob/038c37cac7b906ed73452479147fe1bda97004ee/LICENSE>

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## About this entry

The description was reviewed against primary sources.
Original editorial content: MIT. Linked projects, papers and assets retain their own rights and licenses.