Mostro on Nostr: Mostro uses gift wraps (NIP 59) for mostro–user communication. Each time a user ...

Mostro uses gift wraps (NIP 59) for mostro–user communication. Each time a user creates or takes an order, a new key is derived in their client (NIP 06), so there is no key reuse.

For user-user communication, a shared secret is derived via ECDH between buyer and seller, and messages are then wrapped using gift wraps.

https://mostro.network/docs-english/privacy.html#privacy-in-user-to-user-communication

Deeper: https://mostro.network/protocol/chat.html