Open source hardware signers compared

A hardware signer (often called a hardware wallet) keeps private keys off your computer and signs transactions on the device. This page lists signers whose firmware source code is published, with plain facts about each, so you know what to ask. It is listed alphabetically. It is not a ranking, a recommendation or a buying guide.

Facts checked on 5 November 2026 against each maker's own website and code repository. Products and firmware change, so check the maker's current pages before relying on any detail.

Device	Firmware licence	Bitcoin only?	How it signs	In Sparrow	Secure element
BitBox02 Bitcoin-only edition (including Nova) BitBox also sells a Multi edition that supports other coins	Open source (Apache 2.0)	Yes, in the Bitcoin-only edition	USB-C. Nova also has Bluetooth for iPhone and iPad. Not air gapped.	Yes	Yes (secure chip)
Bitkey A complete 2 of 3 system: a phone app key, this hardware key and a server key held by Block	Open source (MIT). Published for auditing; the maker does not yet support outside builds of every part	Yes	NFC with the Bitkey phone app. USB-C is for charging.	No. Used through its own app, not as one key in a separate coordinator	Yes ("secure enclave", in the maker's words), unlocked by fingerprint
Blockstream Jade and Jade Plus	Open source (GPL 3 collection, per the README)	Bitcoin and Liquid only (no other coins)	QR via camera, USB-C, Bluetooth	Yes	No. Uses a "virtual secure element" with a remote blind oracle instead
COLDCARD (Mk5, Q) Source available, not open source in the strict sense	Source available (MIT with the Commons Clause, which bars selling the software)	Yes	microSD, NFC, USB. Q also has a QR scanner.	Yes	Yes (two, from different vendors)
Foundation Passport Prime Multi-purpose: the maker also offers 2FA codes, security keys, encrypted storage and third-party apps on the same device	Open source (KeyOS mostly GPL 3.0 or later; hardware files published)	Bitcoin wallet built in. Optional Legacy Mode adds Ethereum and Solana-based assets; we cover the Bitcoin wallet only, without Legacy Mode	QR via camera, USB-C (data, optional), NFC (Keycards and security keys), encrypted Bluetooth to the maker's Envoy app, needed for initial setup. No built-in microSD slot or Wi-Fi.	Works as a multisig cosigner with Sparrow, Nunchuk, Specter, Electrum and BlueWallet, per the maker	Yes (one, alongside a security processor)
Keystone 3 Pro with Bitcoin-only firmware The standard firmware is multi-coin	Open source (MIT)	Yes, with the Bitcoin-only firmware	QR via camera, microSD. No USB data, Bluetooth, Wi-Fi or NFC.	Yes	Yes (three)
Krux Do it yourself firmware for off the shelf devices	Open source (MIT and Apache 2.0)	Yes	QR via camera, SD card	Yes	No. Relies on encryption of any stored data
SeedSigner Do it yourself, built on a Raspberry Pi Zero	Open source (MIT)	Yes	QR only. No Wi-Fi or Bluetooth hardware.	Yes	No. Stateless: keys are not stored on the device
Specter DIY Do it yourself from off the shelf parts	Open source (MIT)	Yes	QR (default), USB, SD card	Yes	No. The README lists secure element support as coming soon
Trezor Safe 3, Safe 5 and Safe 7 Bitcoin-only The standard versions are multi-coin	Open source (core firmware GPL v3)	Yes, in the Bitcoin-only versions	USB-C. Safe 7 also has Bluetooth. Not air gapped.	Yes	Yes

Passport Prime. This page lists only devices still on sale. Foundation no longer makes Passport Core, so it is not covered here; Passport Prime is its successor. Prime includes a native Bitcoin wallet, and Legacy Mode, which adds Ethereum and Solana-based assets, is an optional add-on downloaded separately. Our guides assume Prime is used with its Bitcoin wallet only and Legacy Mode is not installed (Foundation FAQ).

"In Sparrow" means the device is in the list of hardware wallets supported by Sparrow, a desktop wallet that can coordinate multisig. Other coordinators, such as Nunchuk, publish their own lists. Bitkey works differently from the rest: it is a complete 2 of 3 multisig on its own, with one of the three keys held on Block's servers, rather than a single signer to combine with others. Prime can be used without its Bluetooth link once set up, signing by QR code or PSBT file only. Foundation's own Envoy app is single signature only, so multisig with Prime needs a separate coordinator. "Air gapped" means the device never connects to a computer for data, using QR codes or a memory card instead.

Known security incidents

Every maker on this page has fixed security flaws, and that is expected: published code invites review, and a published fix often shows open review working. The list below covers selected incidents documented by the maker itself or in a published research write-up, chosen because they touch keys, seeds, firmware or signing. It is not a complete record and not a ranking. Each maker's own advisories and release notes are the full, current source.

Device	Year	What happened	Physical access needed?	Funds lost?	Fixed?
BitBox02	2026	A USB request length was not checked, allowing an out of bounds memory write from a malicious computer. BitBox later rated it severe: with a phishing step to install fake firmware, it could have enabled theft. BitBox02 Nova not affected. Source: BitBox BitBox	No. Needs a malicious computer or app, plus a phishing step for the worst case	None reported by the maker	Yes, firmware 9.26.3 with a bootloader update
BitBox02 and Nova	2026	Found by BitBox's own audit: a memory flaw on Multi edition devices not yet set up (bitcoin-only edition not affected), and a silent payments flaw that could lock funds to an unintended address. Source: BitBox	No. Needs a malicious host computer or app	None reported by the maker	Yes, firmware 9.26.5
Bitkey	2026	Before a new device was set up, someone with an NFC radio close by could set a PIN that might later unlock it. The maker says this alone could not reach funds, as two of three keys are still needed. Source: Bitkey	Yes. NFC range, before setup	None. The maker says it was not enough to access funds	Yes. Current firmware no longer allows PIN unlock
Blockstream Jade	2025	Researchers at DARKNAVY reported a flaw in how firmware 1.0.24 to 1.0.36 read wallet descriptors. On an unlocked device connected to a malicious app over USB or Bluetooth, it could crash the device and, at worst, potentially expose the key. QR mode was not affected. Source: Blockstream	No. Needs an unlocked device and a malicious app	None reported by the maker	Yes, firmware 1.0.37, with 1.0.38 blocking downgrades
COLDCARD (Mk2 to Mk5 and Q)	2026	A firmware weak seed bug: seeds generated on affected releases had far less randomness than intended (about 72 bits rather than 128 on Mk4, Mk5 and Q). Coinkite says the devices were not hacked or remotely accessed, but attackers recreated some weak seeds offline and took funds. Seeds protected by 50 or more private dice rolls, or a strong, unique passphrase, had an extra barrier. Source: Coinkite Coinkite	No. Weak seeds could be recreated offline	Yes, according to Coinkite	Yes for new seeds. Updating does not repair an existing affected seed; Coinkite publishes a migration guide
Keystone 3 Pro	2026	A joint audit with OneKey's Anzen team found a flaw in the chip maker's USB code that, in a lab, allowed the recovery phrase to be extracted. Keystone calls 2.4.0 a critical security update. Source: Keystone OneKey Anzen research	Yes. Needs the device, the PIN, an approved USB connection and the attacker's own computer	None reported	Yes, firmware 2.4.0 (April 2026)
Krux	2026	An anonymous researcher reported a 12 byte buffer overflow in Krux's encrypted backup (KEF) format. The maintainer judged it non-critical. Source: Krux (GitHub)	Not stated	None reported	Yes, v26.09.0
SeedSigner	2026	SeedSigner trusted the coordinator's claims about which outputs were change, so a malicious coordinator could disguise a payment to someone else as change, including in multisig. Source: SeedSigner (GitHub)	No. Needs a malicious coordinator	None documented	Fix merged into the code in September 2026; check the release notes for the first release that includes it
Specter DIY	2026	A security hardening release: the device now rejects output from a failed hardware random number generator, and change outputs must match the wallet's verified descriptor. Source: Specter (GitHub)	Not stated	None documented	Yes, v1.10.5
Trezor Safe 3	2024	Ledger Donjon showed that, with lab equipment and the chip removed from the board, some anti-tampering checks could be bypassed, which could allow a tampered device to be passed on. No key or PIN was extracted. Safe 5 not affected. Source: Trezor Trezor	Yes. Full physical access and specialist tools	None reported. Trezor said no action was needed	Trezor lists it as resolved. Its main advice is to buy from official sources
Trezor Safe 7	2026	The device's authenticity proofs were checked against a combined set of keys, so one valid proof could pass all three chip checks. Each proof is now bound to its own chip. Source: Trezor	Not stated	None reported	Trezor lists it as resolved

No incident is listed for Foundation Passport Prime because we found none in Foundation's own published advisories or on its security page when we checked. That does not mean none exists.

Two habits limit the damage from flaws like these: keep firmware updated from the maker's official source, and in a 2 of 3 multisig, use signers from different makers, so a flaw in one device or one maker's code is not enough to move funds on its own.

What open source does and does not prove

It does

Let anyone read and review the code that handles your keys, rather than trusting a closed product.
Make independent audits and public bug reports possible.
Where the maker offers reproducible builds, let you check that the firmware file you install was built from that published code.

It does not

Prove the code has no bugs. Published code can still contain mistakes, as the record of firmware advisories shows.
Prove the device in your hands is genuine. Buy direct from the maker or an authorised reseller, and use the maker's own checks for tampering.
Cover every chip. Secure elements and other components often run closed code from their own vendors.
Replace good procedures. Keys still need to be created, backed up, stored and tested with care.

For a company

A company holding bitcoin should not rely on a single device or a single person. Our guides describe a 2 of 3 multisig, where any two of three keys can approve a payment. Using signers from different makers for the three keys means one maker's bug or supply problem is not enough to put funds at risk. The key ceremony walkthrough covers creating and testing the keys, and security lessons covers what has gone wrong in practice, including a seed generation advisory from one maker. See known security incidents above.

Not financial advice. No endorsement. No affiliate links. IoT Financial has no commercial relationship with any maker listed here, earns nothing from any link on this page, and does not recommend any product. Inclusion only means the firmware source is published and the facts above could be checked. Speak to a qualified adviser about your own situation.

Sources

Primary sources only. Each link was checked on 29 October 2026. Rules change, so confirm the current version with your adviser.

Next step: your own node. Once the keys, backups and drill are in place, a company can check the chain itself. Running your own bitcoin node.

Education, not advice.

This is general information and education only. It is not financial, investment, tax, accounting, legal or regulatory advice, and it is not a recommendation to buy, sell or hold bitcoin or any other asset. It does not take account of your circumstances or those of your company. You must obtain your own official professional advice to confirm this information is correct before acting on it.

Rules change. This information is correct to our understanding at the last-reviewed date, but it may be incomplete or out of date, and official sources take precedence. Bitcoin is volatile. A company that buys it could lose some or all of the money it puts in.

Using this site does not create an adviser or client relationship. IoT Financial is not authorised or regulated by the Financial Conduct Authority (FCA) and is not registered with the US Securities and Exchange Commission (SEC) as an investment adviser. Read the full disclaimer.

Open source hardware signers

Known security incidents

What open source does and does not prove

For a company

Sources

One email. The whole library.