PACT: Private Automated Contact Tracing - ASB2020/04/20 · • Must wait for Apple & Google apps...

Data Collection Coalition

20 April 2020

PACT: Private Automated Contact Tracing

MAZ 04/20/2020

• All experts say that to exit “stay at home” phase, intensive contact tracing is necessary along with robust testing and focused isolation

• Nobody knows whether manual tracing will be able to scale for COVID-19 in the US

• Smartphone-based automated contact tracing prototyped/implemented in ROK, SG, UK, but…– Privacy concerns there different from US– National health services there vs nothing similar in US

• PACT protocol developed by Prof Rivest at MIT CSAIL assures privacy– “Chirps” generated by Bluetooth when in proximity of another phone– No PII is shared

• Apple/Google announced they will implement OS-based tracing capability consistent with PACT

• Largest remaining engineering challenge: “TOO CLOSE FOR TOO LONG” analytic – “TC4TL”– Estimates distance & duration from Bluetooth signals

• International team led by MIT developing and assessing TC4TL alternatives– Will inform Apple/Google to permit best technical/policy trades for iOS and Android updates

• Discussions underway with several states, cities and public health entities

• Need to address income inequality issues – some communities will benefit less from PACT

Bottom Line Up Front (BLUF)

MAZ 04/20/2020

Animation Video

Animation Video: https://www.youtube.com/watch?v=yuXzAh4slNw

https://youtu.be/g9L0z7EBut4https://www.youtube.com/watch?v=yuXzAh4slNw

MAZ 04/20/2020

General Approach

Approx 6 feet

ChirpLog

Database ofAnonymized

Contacts

BluetoothChirp

RecordsInfectionCertification

ChirpLog

BluetoothChirp

Contact Distance

IndexCase

Contact IndexCase

Contacts

ManualContacts Records

Contact Detection

1 COVID-19 Test Confirmed Positive

2 Exposure Query & Notification

3 Contact Actions

4

CTC Virtual Command Center

ManualNotification

AutomaticQuery &

Notification

Test

Symptom check

SelfQuarantine

Contacts

MAZ 04/20/2020

PACT Layered Stack

Layer 1: Bluetooth Proximity Signaling

Layer 2: Private Cryptographic Protocol

Layer 3A: Public Health Interface

Major Challenges• Bluetooth phenomenology & data collection• Implementing & evaluating “Too Close for Too Long” analytic• Android, iOS interoperability• Operating system policy compliance• Smartphone power constraints• OS vs app functional decomposition

Major Challenges• Privacy preservation• Chirp rollover frequency• Reporting chirps sent vs chirps rec’d• Centralized vs decentralized database

Major Challenges• Integration into manual contract tracing systems• Certification of infection• Interoperability across public heath authorities• Specifying “Too Close for Too Long” boundaries• Encouragement of “opt-in” to citizens

Layer 3B: Citizen InterfaceMajor Challenges

• Clear and local culture-appropriate opt-in instructions and explanation of privacy guarantees

• Simple functionality for reporting and certifying infection

• Simple functionality for notification of possible “too close for too long” contact and related instructions

• Integration with other public health functionality not directly PACT related

MAZ 04/20/2020

Some Design Decisions

Approx 6 feet

ChirpLog

Database ofAnonymized

Contacts

BluetoothChirp


ChirpLog

BluetoothChirp

Contact Distance

IndexCase

Contact IndexCase

Contacts


Contact Detection



3 Contact Actions

4

CTC Virtual Command Center

ManualNotification

AutomaticQuery &

Notification

Test

Symptom check

SelfQuarantine

Contacts

• Send received chirps? transmitted chirps? both?

• Send chirps immediately or when diagnosed positive?

• Send chirps or send seeds?

1• Send contact chirps/seeds (X/R/both)

to cloud and do matching in cloud? or send contact chirps/seeds down to phones and do matching there?

2

MAZ 04/20/2020

Likely June 2020 Scenarioin a Typical State in the U.S.

Approx 6 feet

ChirpLog

Apple/GoogleDatabase of

Anonymized Contacts

BluetoothChirp


ChirpLog

BluetoothChirp

Contact Distance

IndexCase

Contact IndexCase

Contacts


Contact Detection



3 Contact Actions

4

State Dept of Health VirtualCommunity Tracing Center

ManualNotification

AutomaticQuery &

Notification

Test

Symptom check

SelfQuarantine

Contacts

iPhone orAndroid

• Updated Apple & Google OS w/BT contact tracing built in

• Simple state-approved and A|G-approved app for user interface

1

• Apple/Google or otherSynchronized Database

2

• State-approved appwill provide tailoredinstruction to contacts

3

MAZ 04/20/2020

Notional Operator Interface

Confirmed COVID Patient: Justin Morrow

Melissa MorrowScott MorrowBob MorrowKathy MorrowPatricia MorrowMatthew EvansGeorgia EvansLeora BrookeAaron BrookeJoe BondMichael BondEthan JohnsonRebecca Johnson

Patient Reported Contacts

Current Date/Time: 04/15/2020 09:32:14 EDT

Symptom Onset: 04/14/20

TX59237549 45 min 04/08/20 09:34 EDTNE43986904 32 min 04/08/20 19:12 EDTOJ23985789 90 min 04/08/20 20:56 EDTME78954844 32 min 04/09/20 06:34 EDTVM43584374 11 min 04/09/20 09:27 EDTJO23904239 23 min 04/09/20 11:01 EDTEN45890583 45 min 04/09/20 12:03 EDTUR39540858 120 min 04/10/20 09:19 EDTME09596859 19 min 04/10/20 21:23 EDTMT90689068 45 min 04/12/20 23:56 EDTUE90094844 94 min 04/14/20 06:26 EDTME90437238 10 min 04/14/20 07:18 EDT

Tag Duration Date/Time

PACT-Generated Contacts

MAZ 04/20/2020

Operational Implementationvs. Limited-Scale Pilots

OperationalImplementation

(e.g. region or nation)

Pilots(e.g. college dorms,

hospitals, business campus)

• E.g. 100-1K staff, residents• Limited operations, limited

durations• Could proceed prior to Apple &

Google OS updates• Could use custom apps

• Purpose: Learning, preparation, informed feedback to Apple and Google

• E.g. 7M residents in MA• Operations at scale• Must wait for Apple & Google

operating system updates• Must wait for Apple & Google

apps that are approved, one per state per OS

• Purpose: Public health at scale

MAZ 04/20/2020

Technology Might Provide MoreEffective & Efficient Contact Tracing

Probability of False Positive(Apply time, effort, treatment incorrectly on healthy person)

Prob

abili

ty o

f Tru

e Po

sitiv

e(A

pply

tim

e, e

ffort

trea

tmen

t cor

rect

lyon

infe

cted

per

son)

0% 100%

100%

0%

IdealPerformance

ManualTracing

Semi-AutomatedSystem

Operating Point A

Semi-AutomatedSystem

Operating Point B

Better SystemPerformance

Stay at Home(We are here!)

Do Nothing

• We want to give public health authorities the freedom to pick from a range of operating points

• If we estimate Pr(pos), Pr(neg),Cost(FN), Cost(FP), we can find the lowest-cost operating point

MAZ 04/20/2020

“Too Close for Too Long” – TC4TL

Range

Expo

sure

Tim

e

0m

10min

Hug

30min

1hr

8hrs

1m 2m 3m 4m

1min

SameClassroom

Subway,One Stop,Same Car

HandshakeNo Alert

• Public health authorities define alert region• Engineers try to implement it accuratelyALERT!

Side-by-Side@ Coffee Shop

SameTable @School

NotionalAlert Region

MAZ 04/20/2020

Initial Data Collection

Generate “Near” pdfs Generate “far” pdfs

• Empirically measure RSSI vs range for many conditions

– Phone orientation– Location of phone– Phone model – Multipath environment

Probability Density Function of RSSI vs RangeRotation through 3600

RSS

I (dB

m)

Distance (ft)

Prob

abili

ty

RSSI Variability

Data is highly fluctuating, lends itself to a two stage binary detection formulation

MAZ 04/20/2020

Data-Driven R&D

Data Design and Collection

Evaluation Design

R&DEvaluation

DevelopmentSystems

Evaluation onReal Data & Conditions

ResearchEnvironment

Development Environment

Requirements

Technology

International ResearchCommunity

Public HealthAuthorities

Operations

MAZ 04/20/2020

Bluetooth Data w/Ground TruthCollection Coalition

MAZ 04/20/2020

Beginning Formal Data Collection

“AARON” “BOB”

MAZ 04/20/2020

• Phase 0: Proof of Concept– Privacy-preserving design (v1.0) complete– Initial Bluetooth measurements and contact estimator complete

• Phase 1: Risk Reduction and End-to-End System Prototyping– Use-case and CONOPS definition (informed by public health)– Contact estimator refinement and testing campaign– End-to-end system prototype development– User-in-the-loop demonstrations– Analysis of projected utility

• Phase 2: Scale-up and Deployment– Continue to engage with Apple, Google, and find additional partners

• Phase 3: Operations and Continued Support– Will need plan for gathering user feedback / assessing utility from

deployed system

Prototype Development Approach

Current primary focus:Activities underway

Needs strategy and planning groundwork

MAZ 04/20/2020

PACT: Org Chart

Project Leadership TeamRon Rivest (PI)Daniel Weitzner (Co-PI, Privacy)Dr Louise Ivers (Co-PI, Global Health)Israel Soibelman (Co-PI, Strategy)Marc Zissman (Co-PI, Engineering)

Senior Medical Advisory TeamLead: Dr Louise Ivers MD MPH (MGH, HMS)Dr Ilin Chuang MD MPH (USN USFK, O-6)Dr David Walton MD MPH (BWH, HMS)

Engineering

Chief Engineer: John Wilkinson

Chief Architect: Adam Norige

Deputy Chief Engineer:Bobby Pelletier

Privacy Policy

Lead: Danny Weitzner

Members: Lysyanskaya, Shen, Abelson, Shamir, Canetti, etc.

System Analysis

Blue Lead: Chris Roeser

Red Lead: Larry Candell

Private Tracing Protocols

Lead: Emily Shen

Members: Kalai, Shamir, Raskar, Wilkinson, Lysyanskaya, Canetti, Trachtenberg, etc.

Data CollectionCampaign & Evaluation

Data Lead: Marc VieraEval Lead: Doug Reynolds

Site Leads: Jim Houchens (MITRE), David Luzzi (NEU), Paula Ward (MITLL)

Bluetooth Phenomenology

Leads: Jenn Watson &Gary Hatke

Members: Joe Linsky, Anthony Rowe, Swarun Kumar

Policy Outreach & Communications

Lead: Edelman

Members: Weitzner, Soibelman, Edelman, Goldston, Parravano, Zissman

MAZ 04/20/2020

• Ramesh Raskar, MIT Media Lab• Yael Kalai, MIT CSAIL• Dr Bob Deresiewicz, Wellington Mgmt• Dave Suski, MIT LL• David Murcko, MIT LL• Marie Dow, MIT LL• Bryan Mastergeorge, MIT LL• Madeline Chmielinski Malan, MIT LL• Rowena Lindsay, MIT LL• Neila Fitzgerald, MIT LL• Jaymie Durnan, MITLL• Zach Sweet, MIT LL• Tim Gallagher, MIT LL• Dr David Walton, Brigham Wom Hosp, Harvard Med Sch.• Chet Beals, MITLL• Mischa Shattuck, MIT LL• Dr Chris Ziebell, Dell SETON Med Ctr, U of TX• Swaroop Appadwedula, MIT LL• Michael Wentz, MIT LL• Scott Mancini, MIT LL• Shawn Stone, MIT LL• Michael Wang, MIT LL• Mitchell Schmidt, MIT LL• Adam Tse, MIT LL• Randall Seed, MIT LL• Matthew Leahy, MIT LL• Elias Bello, MIT LL• David Goldston, MIT• David Cox, IBM• HON Zach Lemnios, IBM• Nathaniel Hanson, MIT LL• Sean Anklam, MIT LL• Diane Staheli, MIT LL• Sara McGuire, MIT LL• Kajal Claypool, MIT LL

• Ron Rivest, MIT CSAIL• Dr Louise Ivers, MGH, Harvard Med Sch.• Danny Weitzner, MIT CSAIL• Israel Soibelman, MIT LL• Marc Zissman, MIT LL• Adam Norige, MIT LL• Bernadette Johnson, MIT LL• Melissa Choi, MIT LL• Eric Evans, MIT LL• Bob Bond, MIT LL• John Kuconis, MIT LL• COL Dave Pendall, US Army Europe• Bob Loynd, MIT LL• Matt Kercher, MIT LL• Jim Flavin, MIT LL• Ed Wack, MIT LL• Jon Pitts, MIT LL• John Wilkinson, MIT LL• Bobby Pelletier, MIT LL• Dr Ilin Chuang, USINDOPACOM / USFK• Dr Claire Pierre, Harbor Health, Harvard Med Sch.• Ari Trachtenberg, BU• Rob Cunningham, CMU• Jeremy Kepner, MIT LL• Mark Smith, MIT LL• Ramu Bhagavatula, MIT LL• John Meklenburg, MIT LL• Matt Calderon, MIT LL• Mayank Varia, BU• BGen Keith Holcomb, USMC (ret)• John Beatty, Comm of MA• Dr Larry Madoff, Comm of MA• Andrew Heier, MIT LL• Cuyler O’Brien, MIT LL• Megan Richardson, MIT LL• Mike Specter, MIT CSAIL

PACT Contributors (as of 4/5/2020)(Partial List)

Order is stream of consciousness…

• Jenn Watson, MIT LL• Gary Hatke, MIT LL• Marc Viera, MIT LL• Larry Candell, MIT LL• Chris Roeser, MIT LL• Aryeh Feder, MIT LL• Hal Abelson, MIT CSAIL• Maria Zuber, MIT• Dave Granchelli, MIT LL• Brad Dillman, MIT LL• Pat Lincoln, SRI• Adi Shamir, Weizmann Inst• Carl Fossa, MIT LL• Jim Ward, MIT LL• Chris Connelly, MIT LL• Emily Shen, MIT LL• Pam Evans, MIT LL• James Riordan, MIT LL• Anna Lysyanskaya, Brown• Ran Canetti, BU• David Kahn Gilmore, ACLU• Ken Esvelt, MIT Media Lab• Jon Gruber, MIT Economics• Joel Linsky, Qualcomm• Paul Fiore, MIT LL• Mike Wentz, MIT LL• John Mann, MIT LL• Ralph Kohler, AFRL• Kylie Foy, MIT LL• Pat Larkin, MassTech• Carolyn Kirk, MassTech• Joe Zipkin, MIT LL• Chris Smith, MIT LL• Danelle Shah, MIT LL• Brice MacLaren, MIT LL• Bill Streilein, MIT LL

THANK YOU TO ALL CONTRIBUTORS (LISTED AND UNLISTED)!

MAZ 04/20/2020

• All experts say that to exit “stay at home” phase, intensive contact tracing is necessary along with robust testing and focused isolation

• Nobody knows whether manual tracing will be able to scale for COVID-19 in the US

• Smartphone-based automated contact tracing prototyped/implemented in ROK, SG, UK, but…– Privacy concerns there different from US– National health services there vs nothing similar in US

• PACT protocol developed by Prof Rivest at MIT CSAIL assures privacy– “Chirps” generated by Bluetooth when in proximity of another phone– No PII is shared

• Apple/Google announced they will implement OS-based tracing capability consistent with PACT

• Largest remaining engineering challenge: “TOO CLOSE FOR TOO LONG” analytic – “TC4TL”– Estimates distance & duration from Bluetooth signals

• International team led by MIT developing and assessing TC4TL alternatives– Will inform Apple/Google to permit best technical/policy trades for iOS and Android updates

• Discussions underway with several states, cities and public health entities

• Need to address income inequality issues – some communities will benefit less from PACT

Summary

PACT: Private Automated Contact TracingBottom Line Up Front (BLUF)Animation VideoGeneral ApproachPACT Layered StackSome Design DecisionsLikely June 2020 Scenario�in a Typical State in the U.S.Notional Operator InterfaceOperational Implementation�vs. Limited-Scale PilotsTechnology Might Provide More�Effective & Efficient Contact Tracing“Too Close for Too Long” – TC4TLInitial Data CollectionData-Driven R&DBluetooth Data w/Ground Truth�Collection CoalitionBeginning Formal Data CollectionPrototype Development ApproachPACT: Org ChartPACT Contributors (as of 4/5/2020)�(Partial List)Summary

PACT: Private Automated Contact Tracing - ASB2020/04/20 · • Must wait for Apple & Google apps...

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Transcript of PACT: Private Automated Contact Tracing - ASB2020/04/20 · • Must wait for Apple & Google apps...