Oddbean

Seedsigner is a great device. It’s fundamentally different than a coldcard. The main choice is this: do I store seed on device or not? This isn’t exactly a binary choice either…you can store some seed material on device and keep remainder in objectspace and/or meatspace. If you decide that memorizing your seed material makes sense (eg, 12 words without passphrase in the easiest case), then either device will do. As far as storage goes, all the coldcard does is allow you to put a large amount of entropy (12-24 words, 256 dice rolls, passwords or phrases, and/or a combination of the above) behind a small amount of entropy (PIN code) with brute force limited to a small number of attempts. This is a powerful security feature not necessarily needed by some people. When picking a device, consider your long term seed strategy. Are you going to use a 12 word seed and a pass phrase, then punch out a seed plate (https://bitcoinseedbackup.com) and hide the plate? If you die with pass phrase, your coins might be inaccessible if your passphrase was any good. So are you gonna write down passphrase and hide that too? Or maybe tell a friend? Long term key storage is an unsolved problem. Lots of variations on the scavenger hunt and social backup strategies…I’ve been through a few different setups and all I can think to do is involve time, travel, and other humans to slow down unauthorized access to the seed material I make physical…it’s just a matter of time before bad guy gets your coins. But EMP attacks aren’t to be feared. If you trust electronics for storage, which is reasonable through redundancy (eg, get a couple cold cards and store separately), you can trade time for probability…instead of making it take a long time until bad guy gets your coins in the case of physical seed storage, you can give him 10 shots at guessing your pin or the device deletes the private key material in the coldcard storage case. If bad guy gets every coldcard, he can effectively destroy your coins. EMP attacks will yield same result. You can’t have it both ways. But, there are ways to trade on-chain time for reduced complexity seed. You could have it such that any coin not spent for a year, or two, or 5, can now be spent with a different key…presumably one fully existing in some physical object. Sorry for the poorly worded rant. I’ve been thinking about this for over a decade and we are only just now getting to what I hope becomes the future standard: time decaying seed complexity. Maybe someday I’ll write a draft of what I believe to be an ideal strategy. I need to start a company for this and offer it as a service after publishing a DIY guide.