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I mentioned the Trezor earlier particularly Model T where passphrase and recovery seed can be entered on it directly. It has a different model than a typical HSM since it doesn't store anything other than the seed which is combined with entered passphrases to derive wallets/keys.
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It doesn't include any proprietary software and the whole thing is an open design that other people are able to build (and have successfully done so in practice). The primary purpose is for cryptocurrency wallets but it works well for U2F, GPG, SSH and various other purposes too.
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There are definitely options beyond proprietary ones, including options with much different approaches than a traditional HSM storing the keys with / without encryption (ideally with a passphrase entered onto the device). I really like the approach pioneered for Bitcoin wallets.
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Since that lets you generate keys on the hardware wallet, back up the high entropy recovery seed as a phrase, verify you backed it up correctly and then if you need to recover on a new device you can enter it directly onto a new hardware wallet without exposing it to a computer.
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The traditional approach is good if you have existing SSH and GPG keys that need to be moved onto an HSM. I'll definitely prefer the deterministic wallet approach for new keys though. It's not that bad to migrate to new SSH keys but GPG tends to make rotating keys very painful.
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Signing keys for firmware usually can't be rotated at all since they're burned into fuses so that's another case where a more traditional HSM is the best option since existing keys need to be migrated. Android app signing keys were similar, but they've finally added key rotation.
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I need backups for my keys. For a traditional HSM, that means I need to generate them on my computer, back them up onto cold storage and import them onto the HSM. If I ever need to do recovery, I need to expose them to a general purpose computer again too. That's problematic.
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Entering a passphrase directly on the device is another nice property of the Trezor Model T, but a traditional HSM can support that for encrypting keys and still wouldn't have the solid approach to recovery or the deniability from all passphrases leading to valid wallets/keys.
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It's the approach to the security model including recovery, passphrases and on-device input / confirmations that I like rather than the hardware though. I don't want to import keys generated on my computer or expose them to it from cold storage if I need to do recovery, etc.
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