The safest way to verify a COLDCARD firmware download is to begin at the official COLDCARD website, select the release family for your exact hardware, then validate both the OpenPGP signature on signatures.txt and the SHA-256 hash of the downloaded .dfu file. Only after both checks match should you install the firmware. The device performs its own signature checks during installation and boot on the documented Mk4, Mk5, and Q upgrade paths, but that hardware check does not replace verifying the files you downloaded.
Firmware listings, release status, and site navigation can change. Treat the version numbers below as a dated reference, not a permanent “latest” label, and re-check the official downloads page immediately before upgrading.
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Use the official route first
Type coldcard.com into the address bar or open a bookmark you created from the known domain. From there, use the official downloads documentation at https://coldcard.com/docs/downloads/. That page directs owners to the firmware-download route and notes that historical releases remain available for older devices.
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Do not start with a link sent in an email, chat message, forum post, QR code, or social-media reply. A convincing page can use the right product name while delivering a file for another model or a modified binary. Do not use a marketplace seller’s contact page as a firmware source, and never treat a support message as proof that its download link is genuine.
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Check the address bar before downloading. A secure connection indicator is useful, but it is not enough by itself: the domain must be the official COLDCARD domain, and the page should be reached through the site’s own documentation or download navigation.
Confirm the exact hardware and release family
COLDCARD firmware is model-specific. Identify the model from the device itself and then select the matching family on the official all-downloads page. Do not infer compatibility from a similar filename, a shared number, or a release that appears newer.
Models and channels to distinguish
- COLDCARD Mk5 and Mk4: use the standard release family intended for those models.
- COLDCARD Q: use the Q release family, whose version labels include a Q suffix.
- Legacy Mk3 and Mk2: these are listed separately and should not be replaced with a Mk4, Mk5, or Q file.
- Edge builds: the downloads page lists Edge firmware separately from standard releases. An Edge filename is not interchangeable with a standard firmware filename, even when the hardware name looks similar.
The firmware-help guidance says to use only an official firmware file intended for your model. Record the model and release family before saving anything; this simple note makes it easier to detect a wrong download when several browser tabs or files are open.
Download the complete release package
Save the full firmware file, including its .dfu extension, and the signed signatures.txt manifest supplied through the same official release route. Keep the original filenames and place the files in a dedicated folder for that upgrade.
Do not rename a file to make it appear compatible. Do not rely on a filename alone, a screenshot of a checksum, or a checksum copied from an unsigned page. The manifest is the document that binds the published filename and hash to the signed release information.
If you are updating more than one device, keep each model’s files in separate folders. Mixing a Q package with a Mk package can make a later comparison look plausible while checking the wrong release family.
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Verify the OpenPGP signature on signatures.txt
The first verification layer checks that the manifest was signed by the release key and that its signed contents have not changed. Install GnuPG from your operating system’s trusted package source if it is not already available. Import the public key and confirm its fingerprint using the fingerprint and import procedure in the official upgrade guide; do not copy a key from an unsolicited message.
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signatures.txt. - Use the official guide’s key-import instructions, then inspect the key fingerprint and compare it with the fingerprint published by COLDCARD.
- Run the verification command specified by the guide. In a typical GnuPG installation this is
gpg --verify signatures.txt; follow the release page’s instructions if the manifest is supplied with a separate detached-signature file. - Read the complete result. A successful verification reports Good signature.
GnuPG may also display a warning that the key is not certified with a trusted signature. That warning concerns your local trust path for the public key; it is different from a failed cryptographic signature. Resolve the key-fingerprint question through the official instructions before proceeding, and stop if the signature is bad, missing, or made by an unexpected key.
A valid signature proves that the manifest verifies under the public key you used and that the signed manifest content was not altered. It does not, by itself, prove that you obtained the correct public key from an independently trusted channel. That is why the fingerprint comparison matters.
Match the firmware’s SHA-256 hash to the signed manifest
After the manifest passes its signature check, calculate the hash of the exact firmware file you intend to install. Compare the complete value, character for character, with the entry for that filename and version in the signed manifest.
Common local hash commands
- Linux:
sha256sum COLDCARD-release.dfu - macOS:
shasum -a 256 COLDCARD-release.dfu - Windows PowerShell:
Get-FileHash .COLDCARD-release.dfu -Algorithm SHA256
Replace the example filename with the exact name you downloaded. The output must match the manifest’s SHA-256 entry completely; a partial comparison or a visual scan that skips several characters is not sufficient. Copy the two values into a text editor or use a reliable comparison tool if that reduces the chance of overlooking a difference.
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Install only after both checks pass
Once the model, release family, signature, and hash all agree, follow the current official upgrade instructions for your device. Do not improvise a recovery process from an old forum post or from instructions for another model.
The documented upgrade architecture for Mk4, Mk5, and Q devices performs an additional firmware-signature check during installation and checks the firmware signature whenever the system boots. This device-side verification can reject an invalid image, but it is a final safeguard rather than a reason to skip checking the download on your computer.
- Disconnect the device from untrusted computers and prepare the installation media or connection described by the current official instructions.
- Use the verified
.dfufile for the exact model and release family. - Allow the upgrade to finish without removing power or interrupting the documented process.
- When the device reboots, confirm that it completes its own signature check and displays the expected firmware information.
If the device reports an invalid signature, an incompatible model, or an installation failure, stop. Reacquire the files from the official route and repeat the model, manifest-signature, and hash checks instead of trying random firmware files.
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Understand the dated release snapshot
The official all-downloads page displayed the following fixed standard releases dated September 30, 2026. This table records what that page showed at that time; it is not a guarantee that these remain the newest releases.
| Hardware family | Channel | Version shown | Date shown | How to use the information |
|---|---|---|---|---|
| Mk5/Mk4 | Standard, fixed release | 5.6.3 | 2026-09-30 | Use only for a matching Mk5 or Mk4 device after live-page verification. |
| Q | Standard, fixed release | 1.5.3Q | 2026-09-30 | Use only for a matching Q device after live-page verification. |
| Mk3/Mk2 | Legacy listings | Listed separately | Not stated in this snapshot | Do not substitute a current Mk4, Mk5, or Q package. |
| Edge Mk/Q | Edge channel | Listed separately | Not stated in this snapshot | Keep Edge and standard channels distinct. |
Before an upgrade, open the live all-downloads page through the official site and check the release date, model label, channel, and any “fixed” designation. A file can be cryptographically authentic yet still be the wrong choice for your hardware or the wrong channel for your intended installation.
Account for the entropy advisory
Installing a fixed firmware release does not prove that an older seed is safe. The official firmware repository README states that versions from 2021 through July 2026 had a bug that could produce poor entropy. It describes minimum seed-trust thresholds by family:
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| Family | Minimum threshold identified in the advisory |
|---|---|
| Mk4/Mk5 | 5.6.0 |
| Q1 | 1.5.0Q |
| Mk3 | 4.2.0 |
| Edge Mk/Q | 6.6.0 |
The September 30, 2026 standard releases shown on the downloads page are marked fixed, but updating firmware is only one part of the security decision. The repository advisory says that affected existing secrets require action, with the exact response depending on the circumstances and the exception described there.
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If a seed was generated on an affected version, read the complete current advisory and follow its regeneration or migration instructions before treating that seed as trusted. Do not move funds or destroy backups until you understand which accounts, derivation paths, and recovery materials are covered. Firmware verification protects the integrity of the software you install; it cannot retroactively improve randomness used to create an earlier seed.
How to recognize an official support link
The official Firmware Help article is a verified destination for firmware troubleshooting. It was reviewed July 17, 2026 and directs readers toward downloads, upgrade instructions, release history, and device-status checks. Reach it by navigating from the official COLDCARD site rather than accepting a copied URL from a message.
No general purchase-support, account-support, or security-reporting address was established for this procedure. Do not guess a support subdomain, append a path based on a search snippet, or substitute a seller’s contact page. For a non-firmware issue, begin at the official site and use only a support destination linked from there.
Support-link checks
- Confirm that the address uses the official COLDCARD domain and an HTTPS connection.
- Check that the page is reachable from the site’s own navigation, not only from a social post or direct message.
- Be suspicious of urgent requests for seed words, PINs, passphrases, private keys, or remote-control access. A legitimate support page should never require you to disclose wallet secrets.
- For firmware questions, prefer the official Firmware Help destination and the official downloads and upgrade documentation it references.
Troubleshoot a failed verification
The model or filename does not match
Stop the process. Recheck the model shown on the device and return to the all-downloads page through the official route. Do not assume that a similar prefix or a newer-looking number is compatible.
GnuPG reports a bad signature
Do not install the file. Confirm that you imported the public key described by the official guide, verify its fingerprint, and download a fresh copy of signatures.txt from the official release route. If the result remains bad, treat the package as unusable.
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The SHA-256 value differs
Do not “round” or partially compare the values. A mismatch can result from an incomplete download, a corrupted file, or a file from a different release. Delete the suspect firmware, download it again from the official page, and verify the new file against the still-valid signed manifest.
The hash matches but the device rejects the image
Recheck that the matching manifest entry belongs to the exact model and channel. A correct hash proves only that your file matches that signed entry; it does not make a file intended for another model acceptable. Then follow the current recovery instructions for your device.
A page asks for secret wallet information
Close it and do not provide the information. Firmware installation and download verification should never require your seed phrase, private keys, or PIN to be sent to a website or support agent.
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The official firmware repository documents an advanced reproducible-build path for technically capable users. It involves building a specific release from source and comparing the firmware portion with the published binary while accounting for embedded signature bytes.
This is an independent comparison, not a prerequisite for ordinary owners. It requires a reproducible build environment, the exact release source and build instructions, and enough technical skill to interpret binary differences. If you use it, keep the ordinary OpenPGP and SHA-256 checks as the baseline and document the source revision, build environment, and comparison result.
What the verification proves—and what it does not
- OpenPGP signature: the manifest verifies under the public key you selected, and its signed contents have not changed.
- SHA-256 comparison: the firmware bytes on your computer match the filename and hash entry in that signed manifest.
- Device signature check: the covered device verifies firmware during installation and boot.
- Not established by these checks: that you obtained the public key through an independently trusted channel, that the release is right for a different model, or that an old seed generated with poor entropy is safe.
That distinction prevents two common mistakes: treating a filename as compatibility evidence, and treating successful installation as proof that every historical wallet secret is unaffected.
Quick Recap
Printable verification checklist
- Navigate by typing
coldcard.comor using a trusted bookmark. - Open the official downloads documentation and follow its firmware link.
- Identify the exact device model from the device itself.
- Select the matching standard or Edge release family; keep legacy models separate.
- Download the complete
.dfufile and the matchingsignatures.txtmanifest. - Import the official public key and compare its fingerprint using the upgrade guide.
- Verify the OpenPGP signature and confirm a successful “Good signature” result.
- Calculate a local SHA-256 hash and compare every character with the signed manifest entry.
- Install only after all four identifiers—model, channel, signature, and hash—agree.
- Let the device complete its own signature checks during installation and boot.
- Review the current entropy advisory if the seed was generated during the affected period.
- For support, use firmware help reached from the official COLDCARD site and never disclose wallet secrets.
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