A Third Party Service for Providing Trust on the Internet

1. A Third Party Service for Providing Trust on the Internet Work done in 2001 at HP Labs by Michael VanHilst and Ski Ilnicki

2. The Problem • Vendor reputation • this vendor meets high standards • Site authenticity • this is the vendor’s web cite • Page integrity • this is the vendor’s web page • Non-repudiation

3. PKI • The originator has a private key • The receiver has the originator’s public key and uses it to verify data sent from the originator • The receiver verifies the originator’s public key with the stored public key of a well known certification authority

4. PKI Verification The user can verify that: • The public key was issued by the certificate authority (or an agent thereof) • The public key was bound to the name (and URL domain) of the originator • The public key was bound to a period of validity (that includes today)

5. Current Practice • Vendor purchases a certificate • The CA (i.e. Verisign) checks vendor bone fides • Purchaser has valid business license • Purchaser owns domain name • Issues vendor a Digital ID • Vendor attaches Digital ID to pages • ID includes rooted chain of signed keys

6. Current Weaknesses • Business could display Verisign-like seal but not use their certificates* • Business could register with misleading name or URL (visual inspection only!) • amazon.tv or a common mistyping • User could be tricked into accepting untrusted certification authority key • No assurance for unknown businesses

7. Other Threats • Hacked pages on vendor site • Domain name spoofing by poisoning DNS caches with bad IP address (DNS and DHCP don’t use authentication) • A CA gives CA authority to a non-trustworthy individual • Non-trustworthy employee of a CA

8. Naïve Users? Even for obvious spoofs: • Navigate menus for certificate info • under file->properties in IE • under view->page_info in Netscape) • Displayed info has limited value • Go to the myFAU login page and try to find something that positively identifies them.

9. The Threat If a web page asks you for a password or account information, how do you know you can trust it? • How do you know who they are? • Even if you know who they are, how do you know you can trust them? • How does your mother know?

10. Our Proposal Use a trusted third party to perform all verifications and provide assurances • Overcomes most weaknesses in the current practice • Does not require modification to web, browsers, or CA standards

11. 3rd Party Vendor Registration • Vendor registers with 3rd party (e.g., BBB) • 3rd party tracks vendor reputation • Vendor gets PKI ID key pair and 2nd key for private exchange with 3rd Party • Vendor makes modifications to web site to support verification

12. 3rd Party User Registration • User contacts third party (e.g. BBB) (i.e., long before contacting vendors) • User establishes validity of 3rd party in the usual way • User gives Trusted 3rd Party (T3P) a secret string (e.g., “my dog has fleas”) User’s T3P secret cannot be found by trial and error attack – only user verifies it

13. Web Site Verification • User visits web page of a vendor • Vendor page displays seal of T3P Seal has hyperlink with encrypted page URL • User clicks seal, goes to T3P over SSL • T3P verifies vendor & URL • User sees 2nd page with info & secret • User clicks (or redirected) to verified URL, in case seal copied to other URL

14. Site Assurance 3rd Party User Vendor fetch page page fetch assurance assurance + URL refetch page page

15. Site & Content Verification • User visits web page of a vendor • Vendor page displays seal of T3P Seal has hyperlink, encrypted URL+session* • User clicks seal, goes to T3P over SSL • T3P verifies vendor & URL • T3P fetches page & verifies signature • User sees 2nd page with T3P secret • User clicks (or redirected) to verified URL

16. (Session Info) Page could be dynamically generated with session and/or user cookie info • Session and user specific info not available from T3P must be included (encrypted) as parameters to T3P URL • Vendor must support two modes of page generation to allow request from vendor to match that from user

17. Content Assurance 3rd Party User Vendor fetch page page fetch assurance fetch page page assurance + URL refetch page page

18. Proxy Auto Verification • User visits web page of a vendor • Vendor page displays seal of T3P Seal has hyperlink, encrypted URL/session info • User clicks seal, goes to T3P over SSL • T3P verifies vendor & URL • T3P fetches & verifies page signature • User sees frame with T3P secret • User gets verified page from T3P

19. Non-repudiation • User visits web page of a vendor • Vendor page displays seal of T3P Seal has hyperlink, encrypted URL/session info • User clicks seal, goes to T3P over SSL • T3P verifies vendor & URL • T3P fetches & verifies page signature • User sees frame with T3P secret • User gets verified page signed by T3P

20. Proxy & Non-repudiation 3rd Party User Vendor fetch page page fetch assurance fetch page page assurance + page

21. T3P Session Proxy Extension to proxy or non-repudiated • Send all subsequent user requests from page directly through T3P • All hyperlinks on page have T3P’s URL • Links can be recrafted by T3P • or by vendor (but checked by T3P) • Both parties can get T3P signed pages

22. (Cookies) During the proxied session, the vendor’s cookie on the user’s client does not come into play. • At the end of the session, a final step must transfer the session info back to the vendor directly from the user to update the cookie

23. Session Proxy 3rd Party User Vendor fetch page page start session fetch page page assurance + page next request fetch page page assurance + page finish cookie

24. (Included Images) If vendor includes content from other sites • Vendor must provide signed versions of all content • Providers of included content must have their own vendor relationship with T3P • T3P marks parts of page, displayed to user, that are not verifiable