SeedSigner: DIY Bitcoin Signing Device

May 27, 2022

This comprehensive how-to guide walks you through unboxing, setting up and signing bitcoin transactions with the air-gapped SeedSigner device.

This guide by @econoalchemist was published in Bitcoin Magazine.

Contribute.

This guide demonstrates how to self-custody bitcoin using the SeedSigner. SeedSigner is a project that brings together free and open-source code, inexpensive and general-purpose hardware, and a do-it-yourself (DIY) approach to taking personal responsibility of your bitcoin.

Source

Unboxing #

This section demonstrates what is included in the full SeedSigner kit. The kit can be purchased from BTC Hardware Solutions with worldwide shipping available. Alternatively, EU/U.K. customers can purchase the kit from GoBrrr or DIYNodes, and Philippines customers can use TechHaven.

What is Coldcard?

July 3, 2020

⚠️ Critical random number generator vulnerability. Updated 2 August 2026.

A flaw was found in COLDCARD firmware: since 2021 the device silently used MicroPython’s software fallback generator instead of the hardware TRNG. On 30 July 2026, 594.48 BTC were swept from roughly five hundred addresses in a single burst.

Every model except the Mk1 is affected — Mk2, Mk3, Mk4, Mk5 and Q. Fixed firmware: 4.2.0 for the Mk3, 5.6.0 for the Mk4 and Mk5, 1.5.0Q for the Q.

...