Aaron Parecki

Thanks! There's currently no browser API that guarantees the use of secure-element-stored private keys. The best we get now is non-exportable. There's a mention of that here https://datatracker.ietf.org/doc/html/draft-ietf-oauth-browser-based-apps#section-6.3.4.2.2 But as discussed, even hardware-backed keys don't prevent an attacker from starting their own flow in the browser with their own keys.