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@ethankosakovsky
Last active June 11, 2020 12:15
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@adam3us

adam3us commented Apr 26, 2020

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Even worse would be people extracting full paths and putting the master seed manager seed into a standard wallet, so the HMAC there is almost a feature in making that unsupported/incompatible with BIP32 derivation paths below the derived seed.

Very true. No-one needs this standard to in order to export a BIP32 XPRV into another wallet that's looking for it. We'd just be suggesting a subpath to use, which isn't very interesting. Applying HMAC512 as a "firewall" or operational "barrier" is consistent with the rest of this standard and how it works.

So I'll change Coldcard (back) to making XPRV from the HMAC entropy, unless someone gives a reason otherwise.

out of interest which application do you have in mind for the XPRV? is there a coldcard mode for importing them?

@doc-hex

doc-hex commented Apr 26, 2020

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Yes, Coldcard supports XPRV as a master secret (held in secure element). That's why it came up when I implemented this.

@ethankosakovsky

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I have added the reference to Coldcard implementation Coldcard/firmware#39, to the BIP pull request. Everything looks good from my side. Just awaiting the BIP number assignment.

@ethankosakovsky

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This proposal has become BIP85

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