HD wallets are a feature of bitcoin and similar cryptocurrencies with the goal of providing improved privacy and usability. Compelling benefits can be achieved when using non-hardened key derivation. The problem is that if the private key corresponding to an xPub address is somehow leaked, then the private keys of *all* “siblings” and the parent can be exfiltrated. Multi-party computation offers a way to improve this state of affairs because a private key is never in one place (even when signing).

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