1. 2015.9.28

2. - A hospital has a database of patient records, each record containing a binary value indicating whether or not the patient has some form of cancer. - We want to know the total number of patients with cancers? Easy! A summation over these binary values patienthas cancer Amy0 Tom1 Jack1 - But how about if we know anyone must on the list? Or anyone must be the end of the list? Whether Jack has cancer? S(3)-S(2)

3. -If f is a random query function, for example: f(i) = count(i) + noise f(5) : { 2, 2, 5, 3} f(4): {2, 2, 5, 3} with same probability f(5) – f(4) is useless !

4. GIC Incidence [Sweeny 2002] Group Insurance Commissions (GIC, Massachusetts) –Collected patient data for ~135,000 state employees. –Gave to researchers and sold to industry. –Medical record of the former state governor is identified. Patient 1 Patient 2 Patient n GIC, MA DB …… AgeSexZip codeDisease 69M47906Cancer 65M47907Cancer 52F47902Flu 43F46204Gastritis 42F46208Hepatitis 47F46203Bronchitis Name Bob Carl Daisy Emily Flora Gabriel 4 Re-identification occurs! Topic 21: Data Privacy

5. xi xi’ D1 D2 Database neighbors

7. Laplace distribution