Protecting Privacy while using Web Authentication
Web Authentication is a powerful anti-phishing technology that uses hardware authenticators and public-key cryptography to protect your accounts.
A sample of Web Authentication Authenticators
Websites that support Web Authentication are showing a commitment to very high security standards by asking for additional information about your authenticator when you register.
Should I use one authenticator for multiple accounts?
Using an authenticator for one account is safe, but allowing a website to ask for extended information for multiple accounts using the same authenticator can permit that website to identify a link between those accounts.
If you are concerned about having accounts linked together in this way, you should either deny extended information when prompted, or use different authenticators for the different accounts.
This linkability is based on the authenticators, and not on your browser. If you use the same authenticator with different browsers, websites can still identify a link between multiple accounts.