iOS App authentication

Is it possible to let user do in-app authentication such as approving/confirming transaction without redirect to metamask?

You mean without using metamask at all, to do it from your application?

Yeah. Or maybe using metamask SDK if any.

To be more specific, we would want to build an iOS App with full functionality of NFT marketplace. We might want let user to do all the operations in that APP, but we don’t want to make much effort on implementing a “wallet” so just wondering if any existing solution that may fit our requirements.

All transactions must be signed. It’s not a question about user-freindly UI, it’s a question about security and ERC standards.

I see only one possible solution for this - storing private keys in your app and it’s not a secure way.