Yes, our signer is built on the standard NIP-46 spec. We follow the spec precisely, there is nothing proprietary in our implementation.
You don't need to trust Primal with your nsec; our entire stack is open, so you can see precisely how we handling it. The idea behind building a signer is precisely to minimize the need for our users to paste their nsec into any new nostr app they wish to try.
https://nips.nostr.com/46
