Holistic PrivacyFrom Location Privacy to Genomic Privacy

Jean-Pierre HubauxWith contributions from

E. Ayday, M. Humbert, J.-Y. Le Boudec, J.-L. Raisaro, R. Shokri, G. Theodorakopoulos

Make It Faster!!

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Benz Motorwagen, 1885

Ford-T, 1915

After Some Decades…

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… the Concerns Have Changed

• Reduce casualties– Better brakes– Safety belts– Airbags– …

• Mitigate side effects– Road congestion– Depletion of fossil fuel– Climate change– ….

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Similar Phenomenon with IT

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For each end user:

•10s to 1000s Mb/s•Terabytes of storage•Processor in the Ghz

Assault on privacy

Cyber-crime, cyberwar

Information overload,attention deficit disorder

Holistic PrivacyFrom Location Privacy to Genomic Privacy

1. On Privacy Protection2. Location Privacy3. Genomic Privacy

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Another Observation Tool…

“The Right to Privacy”Warren and BrandeisHarvard Law Review

Vol. IV Dec. 15, 1890 No. 5 7

Major concern: photography without consent

Some Modern Observation Tools

8Cellularphones Online Social Networks

Genomicsequencing

Privacy: Definition

• Privacy control is the ability of individuals to determine when, how, and to what extent information about themselves is revealed to others.

• Goal: let personal data be used only in the context they have been released

• Privacy is about the data of individuals

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Main Risk: People’s Mind Manipulation

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Citizens (us)

Those observing us

Privacy Protection at Odds with…

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Privacy Protection

Security (e.g., homeland security)

Business (e.g., targeted advertisement)

Usability

System performance

Medical progress

Holistic PrivacyFrom Location Privacy to Genomic Privacy

1. On Privacy Protection2. Location Privacy3. Genomic Privacy

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Users upload location episodically

through WiFi or cellular networks

Query, Location, TimeQuery, Location, Time

Location-Based Services

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Why Reveal Your Location?

• To use service– Cellular connectivity– Location-based services– Local recommendations– Road toll payment– …

• For social benefits– Find friends

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Can You Clean up Your Digital Trace?

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events-----------------------------------------------

Color: user identityNumber: time-stampPosition on the map: location-stamp

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Threat

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The contextual information attached to a trace tells much about our habits, interests, activities, beliefs and relationships

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Quantification of Location Privacy

• Many privacy-preserving mechanisms proposed

• No unified formal framework in previous work• Various metrics for location privacy

• How to compare different mechanisms?• Which metric to use?

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Time and Space

• Consider discrete time and space

• Attacker: service provider (``honest but curious´´)

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Quantifying Location Privacy

KC: Knowledge Constructor LPPM: Location Privacy Protection Mechanism:-deliberately imprecise coordinate reports (e.g., drop some of the least significant bits)-Swap user identifiers

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Correctness

The adversary’s estimation of x given the observed traces o

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Location-Privacy Preserving Mechanisms

Implemented LPPMs:

Location-Privacy Meter

Open source software tool (C++) to quantify location privacy

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Location-Privacy Meter (LPM)– Some traces to learn the users’ mobility profiles

(background knowledge)– Observed traces

– Location privacy of users with respect to various attacks: Localization, Tracking, Meeting Disclosure, Aggregate Presence Disclosure,…

LPM

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LPM: Example

• N = 20 users• R = 40 regions• T = 96 time instants

• Protection mechanism:– Hiding location– Precision reduction (dropping

low-order bits from the x, y coordinates of the location)

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Attacks

•LO-ATT: Localization Attack: For a given user u and time t, what is the location of u at t?

•MD-ATT: Meeting Disclosure Attack: For a given pair of users u and v, what is the expected number of meetings between u and v?

•AP-ATT: Aggregated Presence Attack: For a given region r and time t, what is the expected number of users present in r at t?

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Results

Protecting Location Privacy:Optimal Strategy against Localization Attacks

Adversary Knowledge:User’s “Location Access Profile”

29Data source: Location traces collected by Nokia Lausanne (Lausanne Data Collection Campaign)

Location Obfuscation Mechanism

Consequence: “Service Quality Loss”

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Location Inference Attack

Estimation Error: “Location Privacy”

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Problem Statement

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Zero-sum Bayesian Stackelberg Game

User Adversary (leader) (follower)

Game

LBS message

user gain / adversary loss

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Optimal Strategy for the User

Proper probability distribution

Respect service qualityconstraint

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Optimal Strategy for the Adversary

Note: This is the dual of the previous optimization problem

Proper probability distribution

Shadow price of the service quality constraint .(exchange rate between service quality and privacy)

Minimizing the user’s maximum privacy under the service qualityconstraint

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Evaluation: Obfuscation Function

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Output Visualization of Obfuscation Mechanisms

Optimal Obfuscation Basic Obfuscation(k = 7)

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Conclusion on Location Privacy• Protecting location privacy is a major challenge• Quantification expressed as adversary’s expected estimation error

(incorrectness)• Techniques to protect location privacy: introduce imprecision in the

reported location, reduce location report frequency, make use of pseudonyms,…

• Privacy (similarly to any security property) is adversary-dependent. Neglecting adversary’s strategy and knowledge limits the privacy protection

• More information and pointers:http://lca.epfl.ch/projects/quantifyingprivacy

Holistic PrivacyFrom Location Privacy to Genomic Privacy

1. On Privacy Protection2. Location Privacy3. Genomic Privacy

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On Convergence…

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``The last inch´´

Digital medicine:- Digital medical records- Digital imaging-Medical online social networks-Genome sequencing-Other ´omics data- Wireless biosensors…

Telecom Computing

ICT

…0100110100011… …CGTTAATTCCGTA…

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The Genomic Avalanche Is Coming…

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Genetic Sequencing

GATTACA (1997 Movie)

Basics of Genomics – 1• A full genome sequence:

– uniquely identifies each one of us

– contains information about our ethnic heritage, disease predispositions, and many other phenotypic traits.

• Human genome: 3 billion letters

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Basics of Genomics - 2

• The cell’s nucleus holds the genetic program that determines most of our physical characteristics.

• This information is stored in chromosomes.• Billions of identical copies of the genetic program, one for each cell

nucleus.

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Basics of Genomics – 3

• Chromosomes: molecules of a double-stranded chemical known as Deoxyribonucleic acid (DNA)

• DNA consists of chemical units that hook together known as nucleotides

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Basics of Genomics – 4

• DNA has two strands and four nucleotides (A T G C):

• A = Adenosine• T = Thymidine• G = Guanosine• C = Cytidine

• The genetic information is stored in the exact sequence of nucleotides.Pairs: A-T and G-C

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Basics of Genomics – 5

Human Genome complete and ordered sequence of all 23 chromosomes

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Basics of Genomics - 6

• Human Genome identical in most places for all people.

• SNP (Single Nucleotide Polymorphism) positions where some people have one nucleotide pair while others have another.

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Basics of Genomics – 7

• SNPs make up only 1.3% of the genome

• The differences at these places make each of us unique

Allele designates which nucleotide is present at a SNP.

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40 million SNPs

… … ……

Summary of Key Concepts

• Our genetic information is stored in the sequence of DNA in our chromosomes.

• There are 23 chromosomes in a human genome. Men and women have slightly different sets of chromosomes.

• SNPs are chromosome addresses. They are spots where some people have one nucleotide, while others have another.

• SNPs have four possible alleles: A, T, G, and C.• Our collection of SNP alleles is what makes each of us unique.• Modern techniques make it possible to determine the status

of large numbers of SNPs very efficiently.

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From the Sample to the Full Genome Sequence

Raw data(FASTq)

Full genome

• Individual diagnosis,personalized medicine

• Statistics

Deep / ultra-deep sequencing

SAM file (aligned reads)

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Samples Sequencing machine (Illumina,

Roche, Life Technology,

Oxford Nanopore,PacBioScience,…)

Threat

• Leakage of genomic data• Revelation of privacy-sensitive data about the

patient – Predisposition to disease, ethnicity, paternity or

filiation, etc.– Denial of access to health insurance, mortgage,

education, and employment• Cross-layer attacks

– Using privacy-sensitive information belonging to a victim retrieved from different sources

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Goals

• Allow specialists to access only to the genomic data they need

• Protect data, including from insiders (e.g., curious sysadmins) homomorphic encryption

• Access time to a single patient’s genomic data below a few seconds

• Access time to the data of a cohort of thousands of patients below a few minutes

Cryptographic Tools

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Possible Solution

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5) “Check my susceptibility to disease X”and part of P’s secret key, x(2)

3) Encrypted variants

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7) Homomorphic operationsand proxy encryption

Patient (P)Medical Center

(MC)

1) S

am

ple

Certified Institution Curious Party@ SPU

Malicious 3rd party

Storage and Processing Unit(SPU)

2) Sequencing and encryption

4) Part

of P’s

secre

t key, x

(1)

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Probabilities:

. . .

Markers for disease X:

P’s SNPs:

Contributions

of markers:

P’s susceptibility for disease X:

. . . . . . . . .

Disease Susceptibility – Weighted Averaging

• All operations are conducted in ciphertext using homomorphic encryption. 57

Prototype – Patient Interface

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Prototype – SPU Interface

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Prototype – Medical Center Interface

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Holistic Privacy: Data about an Individual

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Genome

Human Relationships

Mobility+ Body Area Network

Conclusion on Genomic Privacy• Digital medicine is coming• It will for ever change the landscape of privacy

protection• Genomics is particularly relevant and there is a huge

ongoing research effort• Highly sensitive data + huge amounts of data + complex

correlations between data Complex field, Big Data• Tools (cryptography, security protocols,

database/differential privacy, anonymization techniques,…) already used for privacy protection in ICT can (and should) be applied here

• More information and pointers: http://lca.epfl.ch/projects/genomic-privacy/

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Overall Conclusion• Assault on privacy huge research challenges • Location privacy

– quantifiable at the physical level ( (x, y) coordinates)– ongoing work at the semantic level

• Online Social Networks part of the background knowledge of the adversary

• Genomic privacy – still in its infancy– soon to be very hot – first results coming out

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