Privacy¶

Privacy¶

Determine when/how/what information is communicated to others
Aspects
Right to be let alone
Self-identity / personal growth
Protection intimate relationships
Data privacy: Detect/control data inference
DB Security: Control access / protect content
Challenge: Utilize data while protect individuals privacy
Idea: Anonymize all attributes that could be used for de-anonymization

Privacy: Risks + Protection¶

Problem: Growing availability of information
Who is allowed to see what?
Goal: Anonymize data
Protection technique: Formal models
Specify privacy model
Derive conditions
Design algorithms satisfying privacy conditions
Example: K-anonymity, L-diversity, L-closeness, (c,k)-safety

k-Anonymity¶

Protection model, ensure anonymity in relational data
Idea: Generalize, modify, distort identifiers -> no unique identification
Definition: R(A1, … An), Quasi-identifiers
R satisfies k-Anonymity <=> each sequence R[QI] at least k times
Meaning: Matching cannot reduce to fewer than k individuals
Large k => higher privacy
Find quasi-identifiers: Hard / impossible
Algorithm (NP-hard)
Delete cell values / tuples (generalization causes information loss)
Generalize cell values (quasi-identifiers)

Attacks¶

Unsorted matching attack:
Data often sorted, sort data
Complementary release attack:
Two data sets, match with problem attribute
Homogeneity attack:
Problem attribute for class is same (little diversity)
Background knowledge attack:
Very complex attack (knowledge not known)

L-Diversity¶

Prevent homogeneity / background knowledge attack
Sensitive attributes in a class must be L different values
No perfect anonymization (Binary attribute hard to achieve, distribution not considered)

Curse of Dimensionality¶

Data many attributes
Data sparse
K nearest neighbors are far away
Result: Loss of information

Sparse data: Deanonymization¶

no quasi-identifiers
Netflix: K-Anonymization generalization high data loss
Idea:
Calculate similarity Netflix and IMDB
Most similar record is a match
No record: Candidates also reveal information
Information:
political orientation
Religious views