Re:Microsoft Confirms Password Deletion for 1B Users
by lxgr on Tuesday December 17, 2024 @03:45PM
(#42445130)
Authenticating yourself with a passkey cryptographically signs a challenge issued by the site you're trying to log in at, and your WebAuthN client (usually your browser) only signs challenges it knows about.
The important point here is that there is no way for you to have your browser sign an arbitrary (e.g. an attacker's) challenge, since you can't input the challenge at all.
This makes WebAuthN strictly better than static passwords, TOTPs (which are "unidirectional" in nature), and even "enter code 123456 into your authentication device and provide the code it displays"-like flows (which is a bidirectional challenge-response, but a MITMable one).
The important point here is that there is no way for you to have your browser sign an arbitrary (e.g. an attacker's) challenge, since you can't input the challenge at all.
This makes WebAuthN strictly better than static passwords, TOTPs (which are "unidirectional" in nature), and even "enter code 123456 into your authentication device and provide the code it displays"-like flows (which is a bidirectional challenge-response, but a MITMable one).