Coronalert: Privacy‐Preserving Proximity Tracing

Bart PreneelBart.Preneel(AT)esat.kuleuven.be @cosic.be

27 August 20201

Contact tracing = essential to control epidemic

• Very privacy invasive • Slow • Accuracy:• human memory • what with contacts with strangers?

• Privacy by design• Faster• More accurate

• false positives/negatives• also with strangers

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Manual (contacts) App (proximity)

Not too many infections Sufficient testing Sufficient capacity

Conditions: 

complementary

Goal of contact tracing

• Warn citizens at risk• Encourage citizens to undergo a test or to go in quarantine

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• Accurate• Privacy friendly• Voluntary• Transparency• Works at EU scale (October)

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TEKA TEKB

TEKD

TEKA TEKB

TEKD

RPIA1RPIA2RPIA3RPIA4

RPIB1RPIB2RPIB3RPIB4

RPID1RPID2RPID3RPID4

RPIA3

RPID1

RPIB4

StoreRPID1RPIC2

TEKC

RPIC1RPIC2RPIC3RPIC4 TEKC

StoreRPIA3RPID1

RPID2

storeRPIA3RPIC2

installation operation

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TEKD

TEKA TEKB

TEK*

StoreRPID1RPIC2

TEKC

StoreRPIA3RPID1

StoreRPIA3RPIC2

TEKDTEKD

TEKD

TEKD

TEKD

TEKD

test proximity tracing

TEKD

TEKD

TEKA

RPIA3

RPID1RPIB5

TEKB

RPIA3RPID1RPIA1

RPIB5 RPIA3RPIB5

RPID1

TEKDTEKD

overview

TEKD

Details: GP visit

Do you have symptoms?If yes: day of onset of 

symptoms? 

Date (infectious)Test number (15+2)

RAG: Date patient became infectious= two days before onset of symptomsor = two days before day of test (if asymptomatic)

Date (infectious)Test number (15+2)

INSZ

2 check digits to detect typos

eform: COVID‐19 LAB REQUEST (1/2)

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eform: COVID‐19 LAB REQUEST (2/2)

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eform: COVID‐19 OVERRULE LAB RESULT 

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eform: COVID‐19 SUSPECTED CASE

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TEKD

Details: sampling location

Do you have symptoms?If yes: day of onset of 

symptoms? 

RAG: Date patient became infectious= two days before onset of symptomsor = two days before day of test (if asymptomatic)

Webform

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Screenshots Coronalert on iOS

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Screenshots Coronalert on iOS

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Screenshots Coronalert on Android

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