Seedhammer Review – Stamp your Bitcoin multisig into steel

Note: Seedhammer reached out over DMs in regards to some of my points below. Please read their notes. I’m not going to edit my review, but they have some valid points that contradict some of what I note below.

The Seedhammer is a machine that is designed to stamp your Bitcoin seedphrase into steel for you. Specifically, the value prop is being able to stamp a multisig 2 of 3 or 3 of 5 into the appropriate amount of plates, along with the descriptors. This makes it so that you can recover your multisig wallet with the minimum number of plates required by the quorum. If this works as advertised, it would make for a much better solution then the requirement that all xpubs be backed, along with all of the keys, in order for wallet recovery. Current cost is around $600 USD just for the machine, not counting the plates. I bought the machine, plus several plates of the different types offered. I spent roughly ~3 million sats.

I sort of knew what to expect when I ordered this – a machine built for industrial purposes that a bitcoiner repurposed to sell as a seed backup system. It’s a dumb machine by default – no computer on board. It requires a controller in order to direct it. The Seedhammer uses the same hardware as a Seedsigner in order to do that, but with Seedhammer software. All of this is to replace 3rd party services (like Unchained Capital.) A 3rd party multisig service is there to ensure you in case you mishandle the backup of your wallet, or potentially to help your loved ones recover the wallet in case they need that help. The Seedhammer makes it so that you can be much more comfortable with not using a 3rd party as backup and instead stay self-sovereign.

For comparisons sake, Unchained Capital charges $350 for their basic multisig vault package, plus signing device costs. There is also an option that costs nothing for those that know what they are doing, however there are costs of signing devices, and add-on charges in case you need help.

The device ships well packed in what I think is the original packing material, with whatever plates you order added on top. There are some included USB cables and an adapter that let’s it connect to your Seedsigner.

Does the Seedhammer work as advertised?

Yes, Seedhammer works as expected. I was able to setup a multisig and recover the wallet using the minimum amount of plates required to sign a transaction, and I was able to do that recovery multiple times using different key combinations of the 5 plates. In the case of a 3 of 5 setup, each plate has 2 QR codes on the descriptor side and 1 QR code on the side that has the mnemonic stamped. Everything scanned fine with a little bit of adjusting the camera. The plates reflect light, which is not great for scanning a QR code, and you also need enough light to be able to scan… That means it takes a little bit of work to get that dialed in just right. The QR code that contains the mnemonic is the easiest to scan since it’s smaller and doesn’t have near as much info as the descriptor QR codes.

What to watch out for using Seedhammer

I did screw up one thing. A little context here… The seedhammer software that you install on a micro SD card and put into a Seedsigner is very basic. And that’s a good thing. It makes it easy to look at the code if you are so inclined, and it also makes it so that it’s very straightforward in terms of using it for it’s intended use. When you turn it on it is immediately working towards the intended goal of stamping a seed into metal, so with that in mind it is important for you to be ready to do just that. The first option it gives is to stamp a single sig or multi sig. When you choose the type you are backing up, it then tells you to pull the micro SD card, giving you a little more assurance that it is not logging seeds. And if you are starting with your multisig setup, the software requires that you go from start to finish with no interruption to power for the controller (the seedsigner hardware.) Also, each plate takes time to stamp. And the 3 of 5 setup in particular takes hours to work through.

In my case I had my seedsigner plugged into a battery instead of an outlet, and that batter was down to almost nothing in the middle of building my wallet. I had to stop the process (unplug the controller,) and restarting meant starting again from the very beginning. I compensated for that by lifting the needle on machine so that it wasn’t actually stamping anything until I got to the plate number that I needed to start stamping. It would have been nice to be able to tell the software that I had already started stamping and where in the process I was at.

So, who is Seedhammer for?

There are a few very specific use cases for this machine. You can stamp single sig wallets, 12 or 24 words. Or multi sig wallets, 2 of 3 or 3 of 5, with either 12 or 24 words. The Seedhammer will not do a multisig outside of what I note above. Also, seedhammer will only stamp 12 or 24 words mnemonics. If you just need to backup a single sig this machine is giant overkill. The best use case for Seedhammer then is to setup a multisig for inheritance purposes without needing a 3rd party. There are much cheaper options for stamping a single sig into steel ( What you are paying for here is to be able to backup your multi sig without anyone else being involved, knowing that you or your loved ones can recover the wallet as long as there are the minimum amount of plates required to sign, and not needing any 3rd party to help with any of that backup or recovery process.

And then, after you’ve stamped your multisig wallet into steel, and confirmed that you can recover the wallet, you should probably dismantle the machine and discard it. Yes, I am suggesting that you throw away your shiny new $600 industrial device. There is not much left to do with it after you’ve finished backing up the seeds you intend to backup. You shouldn’t trust that the machine didn’t log your seeds, so that means you can’t resell it. The one other use case is to be an Uncle Jim to friends and family that would like steel backups. This use case requires them to trust you with their seed phrases. It’s not good for anything else, unless you know about this machine and how to make adjustments to it. Speaking of which…

Questions I have about this machine

I am not sure what the lifespan of the needle is, or how many plates you can stamp before the machine needs maintenance. And I could not find any info about that on the seedhammer homepage. I also could not find who manufactures it, or where information about the machine can be found. It would be nice to know how to get a new needle if needed, or how to maintain the machine, and when to do that.

Effectively you are paying $600+ USD to do a really good multisig steel backup. Is that worth it? In my case, yes. I would never have used a 3rd party, and I had a hard time trusting that my loved ones would have done a good enough job saving xpub backups for all seeds. This backup system gives me the peace of mind I need to fully move to multisig for Bitcoin that I intend to pass down to my kids.

Who a Seedhammer is not for

It’s not for anyone that doesn’t need a self-sovereign multisig backup solution. If you intend to use a 3rd party, like Unchained, then you don’t need this. If you are using a single sig wallet, then you have no need for the Seedhammer.

A note from the Seedhammer team

Seedhammer was good enough to reach out to me over DMs on Twitter to share some feedback in regards to my questions, and my experience with using their machine and software. It’s relevant to my review because it appears I was wrong about not being able to start and stop the software when stamping a multisig. Also, they answer a few of my question about the machine itself. I will past the DMs below. This was a Twitter DM convo, so apologies for the grammar.

You have very few misleading information, some that you couldn’t know about unless you read github and our website-articles etc.

1) There is a dryrun-option in order to “print” without hammer strokes:

You can after first side is dry-run’ed switch dry-run off again same way you turned it on. In order to print second side only. Imagine second side got corrupt – or you just want spare descriptor plates.

This is also usable if you got interrupted in between first and second side.

2) It is not quite true that you have to stamp all plates in one long run. You can always change battery on your SeedSigner between plates (and even sides, see above). Then load the descriptor again, and input desired seed, when asked. No need to provide seed #1 – you can backup seed #5 as the first one if you want. As the only one actually.

It’s made like this on purpose, in the case you need to travel in between hammering-sessions (some like to hammer locally in order not to move finished plates across borders etc). And it helps with people, who need to change battery on the controller.

3) SeedHammer will do any of the multisigs mentioned here: – and we do work on supporting _any_ multisig combo. But still need some thinking on that one!