NIP-60: clarify privkey is optional

[patrickReiis]

I am learning Cashu for the first time, so this may not make sense.

However, if I understood correctly, to redeem/spend a Cashu with a spending condition, you need a corresponding private key to sign the Proof. In the context of Nostr, this private key can be the user's own Nostr private key or another private key, not related to the user's Nostr private key.

So, if the client is using the user's own Nostr private key, then the privkey tag wouldn't be needed, correct?

[pablof7z]

To spend a p2pk-locked cashu you need to sign a non-nostr payload; which is not supported (and won't be supported) by NIP-07 or NIP-46. Tha effectively means that a p2pk-locked to the user's nostr pubkey can only be spent with direct access to the user's nsec (i.e. no nip-07/46 login)

This privkey in the wallet event allows to specify a different pubkey JUST for the p2pk lock so when someone nutzaps that user they lock to it.

This enables clients that don't have access to the user's nsec to redeem the nutzaps.

As a byproduct of this, this completely independent private key can be used to generate recoverable-ecash just like Cashu.me and other wallets do to generate cashu that can be recovered from a seed.

[patrickReiis]

Oh now I see it, thanks.

But is this merge request still correct though? I think most clients will prefer to use privkey, but since it's possible to use the user's nsec, then it makes sense to highlight that privkey is optional, no?