1. Targeted Advertising… and Privacy Too Ari Juels RSA Laboratories Buy me!

2. Targeted advertising: One View Anti- dandruff Buy me! Anti-wrinkle Cream Buy me too!

3. An example Special Report: October 5th is America's October 5th is America's most popular birthday.

4. Anybirthday.com targeted gift recommendations Hiking/sports book Anti-aging cream

5. Targeted advertising: The benign view Advertiser Consumer What shall I read next? Anna Karenina Red Chamber Wild Things Bleak House Here are some novels you might enjoy

6. The other view: Consumer privacy Consumer Browser cookies

7. Our Goal Advertiser Consumer + Privacy Efficiency

8. Private Profile Physical characteristics: Age: 30 Weight: 120 Height: 5’ 4” …. Hobbies: Butterfly collecting Tai Chi Archery Favorite foods: Chocolate Sushi Broccoli Financial (from Quicken): $110,000 / year income House worth $300,000 $20,000 butterfly collection Web sites recently visited (from browser): aclu.org yahoo.com anybirthday.com

9. Negotiant Advertiser Profile Ad request

10. Negotiant Advertiser if annual income > $100,000 if likes funny clothes or CEO output “golf ad” else if female output “spa ad” else output “cigar ad” else output “Walmart ad” Alice “spa ad”

11. Private Information Retrieval (PIR) Alice’s computer Negotiant “spa ad” Ads Advertiser’s server Spa ad Problem: Expensive!

12. Scheme 1: Naïve PIR Alice’s computer Negotiant “spa ad” Ads Advertiser’s server Ads Spa ad Problems: Inefficient; no idea what ads were distributed

13. Scheme 2: Direct request Alice’s computer Negotiant “spa ad” Ads Advertiser’s server “spa ad” please Spa ad

14. Basic tool: Mix network plaintext 1 plaintext 2 plaintext 3 plaintext 4 Randomly permutes and encrypts inputs Mix network

15. Opposite direction Randomly permutes and decrypts inputs Mix network plaintext 1 plaintext 2 plaintext 3 plaintext 4

16. Scheme 3: Semi-private PIR Alice’s computer Ads Advertiser’s server Bob’s computer Carol’s computer Darius’s computer Mix network “Walmart ad” “golf ad” “spa ad” “golf ad” “Walmart ad”

17. Scheme 3: Semi-private PIR Alice’s computer Ads Advertiser’s server Bob’s computer Carol’s computer Darius’s computer Mix network Walmart ad golf ad spa ad Spa ad spa ad golf ad Walmart ad

18. Scheme 3: A little more detail Alice, ad request name, “spa ad”

19. name, “spa ad” Scheme 3: A little more detail name Spa ad, Alice, ad

20. Remarks u We assume advertiser may collude with some mix servers (if not, one-server mix will do) u Ads are long, so we need a hybrid mix network –New constructions: OA00,JJ01 u Other tools –Quorum controlled threshold proxy re- encryption u Aggregation and mixing can be offline

21. Malicious negotiant Negotiant Advertiser Profile “ad $110,000” please ad number = annual income

22. Spotting Malicious Negotiants u Open source negotiants u “Sandbox” approach u Third-party validation

23. Scheme 4: Threshold PIR u Full set of ads mixed u Full privacy u Plaintext Equality Testing (PET) primitive needed u High cost (still better than PIR)

24. What are the (hoped for) benefits? u More consumer trust –Higher “opt in” rate –Truth in (requested) advertising u Complementary with P3P u Mobility possible through encrypted profile on server

25. Questions?