<s>
Digital	B-Protocol
contact	I-Protocol
tracing	I-Protocol
is	O
a	O
method	O
of	O
contact	O
tracing	O
relying	O
on	O
tracking	B-Operating_System
systems	I-Operating_System
,	O
most	O
often	O
based	O
on	O
mobile	O
devices	O
,	O
to	O
determine	O
contact	O
between	O
an	O
infected	O
patient	O
and	O
a	O
user	O
.	O
</s>
<s>
It	O
came	O
to	O
public	O
prominence	O
in	O
the	O
form	O
of	O
COVID-19	B-Application
apps	I-Application
during	O
the	O
COVID-19	O
pandemic	O
.	O
</s>
<s>
Since	O
the	O
initial	O
outbreak	O
,	O
many	O
groups	O
have	O
developed	O
nonstandard	O
protocols	O
designed	O
to	O
allow	O
for	O
wide-scale	O
digital	B-Protocol
contact	I-Protocol
tracing	I-Protocol
,	O
most	O
notably	O
BlueTrace	B-Protocol
and	O
Exposure	B-Application
Notification	I-Application
.	O
</s>
<s>
When	O
considering	O
the	O
limitations	O
of	O
mobile	O
devices	O
,	O
there	O
are	O
two	O
competing	O
ways	O
to	O
trace	O
proximity	O
:	O
GPS	O
and	O
Bluetooth	B-Protocol
;	O
each	O
with	O
their	O
own	O
drawbacks	O
.	O
</s>
<s>
On	O
10	O
April	O
2020	O
,	O
Google	B-Application
and	O
Apple	O
jointly	O
announced	O
that	O
they	O
would	O
integrate	O
functionality	O
to	O
support	O
such	O
Bluetooth-based	O
apps	O
directly	O
into	O
their	O
Android	B-Application
and	O
iOS	B-Application
operating	B-General_Concept
systems	I-General_Concept
.	O
</s>
<s>
Digital	B-Protocol
contact	I-Protocol
tracing	I-Protocol
has	O
existed	O
as	O
a	O
concept	O
since	O
at	O
least	O
2007	O
,	O
and	O
it	O
was	O
proven	O
to	O
be	O
effective	O
in	O
the	O
first	O
empirical	O
investigation	O
using	O
Bluetooth	B-Protocol
data	O
in	O
2014	O
.	O
</s>
<s>
A	O
2018	O
patent	O
application	O
by	O
Facebook	O
discussed	O
a	O
Bluetooth	B-Protocol
proximity-based	O
trust	O
method	O
.	O
</s>
<s>
The	O
concept	O
came	O
to	O
prominence	O
during	O
the	O
COVID-19	O
pandemic	O
,	O
where	O
it	O
was	O
deployed	O
on	O
a	O
wide	O
scale	O
for	O
the	O
first	O
time	O
through	O
multiple	O
government	O
and	O
private	O
COVID-19	B-Application
apps	I-Application
.	O
</s>
<s>
Many	O
countries	O
,	O
however	O
,	O
saw	O
poor	O
adoption	O
,	O
with	O
Singapore	O
's	O
digital	B-Protocol
contact	I-Protocol
tracing	I-Protocol
app	O
,	O
TraceTogether	B-Application
,	O
seeing	O
an	O
adoption	O
rate	O
of	O
only	O
10-20	O
%	O
.	O
</s>
<s>
COVID-19	B-Application
apps	I-Application
tend	O
to	O
be	O
voluntary	O
rather	O
than	O
mandatory	O
,	O
which	O
may	O
also	O
have	O
an	O
impact	O
on	O
the	O
rate	O
of	O
adoption	O
.	O
</s>
<s>
Experts	O
also	O
criticized	O
protocols	O
like	O
the	O
Pan-European	B-Protocol
Privacy-Preserving	I-Protocol
Proximity	I-Protocol
Tracing	I-Protocol
and	O
BlueTrace	B-Protocol
for	O
their	O
centralized	O
contact	O
log	O
processing	O
,	O
that	O
meant	O
the	O
government	O
could	O
determine	O
who	O
you	O
had	O
been	O
in	O
contact	O
with	O
.	O
</s>
<s>
MIT	O
SafePaths	O
was	O
also	O
the	O
first	O
to	O
release	O
a	O
privacy-preserving	O
Android	B-Application
and	O
iOS	B-Application
GPS	O
app	O
.	O
</s>
<s>
Covid	B-Application
Watch	I-Application
was	O
the	O
first	O
organization	O
to	O
develop	O
and	O
open	O
source	O
an	O
anonymous	O
,	O
decentralized	O
Bluetooth	B-Protocol
digital	B-Protocol
contact	I-Protocol
tracing	I-Protocol
protocol	O
,	O
publishing	O
their	O
white	O
paper	O
on	O
the	O
subject	O
on	O
20	O
March	O
2020	O
.	O
</s>
<s>
The	O
protocol	O
they	O
developed	O
,	O
the	O
CEN	O
Protocol	O
,	O
later	O
renamed	O
the	O
TCN	B-Protocol
Protocol	I-Protocol
,	O
was	O
first	O
released	O
on	O
17	O
March	O
2020	O
and	O
presented	O
at	O
Stanford	O
HAI	O
's	O
COVID-19	O
and	O
AI	O
virtual	O
conference	O
on	O
April	O
1	O
.	O
</s>
<s>
NOVID	O
is	O
the	O
first	O
digital	B-Protocol
contact	I-Protocol
tracing	I-Protocol
app	O
which	O
primarily	O
uses	O
Ultrasound	O
.	O
</s>
<s>
Their	O
ultrasound	O
technology	O
yields	O
much	O
higher	O
accuracy	O
than	O
Bluetooth-based	O
apps	O
,	O
and	O
they	O
are	O
currently	O
the	O
only	O
app	O
with	O
sub-meter	O
contact	O
tracing	O
accuracy	O
.	O
</s>
<s>
Bluetooth	B-Protocol
,	O
more	O
specifically	O
Bluetooth	B-General_Concept
Low	I-General_Concept
Energy	I-General_Concept
,	O
is	O
used	O
to	O
track	O
encounters	O
between	O
two	O
phones	O
.	O
</s>
<s>
Typically	O
,	O
Bluetooth	B-Protocol
is	O
used	O
to	O
transmit	O
anonymous	O
,	O
time-shifting	O
identifiers	O
to	O
nearby	O
devices	O
.	O
</s>
<s>
Bluetooth	B-Protocol
protocols	O
with	O
encryption	O
are	O
perceived	O
to	O
have	O
less	O
privacy	O
problems	O
and	O
have	O
lower	O
battery	O
usage	O
than	O
GPS-based	O
schemes	O
.	O
</s>
<s>
Another	O
serious	O
concern	O
is	O
the	O
potential	O
inaccuracy	O
of	O
Bluetooth	B-Protocol
at	O
detecting	O
contact	O
events	O
.	O
</s>
<s>
Smartphone	O
GPS	O
logging	O
solutions	O
are	O
more	O
private	O
than	O
Bluetooth	B-Protocol
based	O
solutions	O
because	O
the	O
smartphone	O
can	O
passively	O
record	O
the	O
GPS	O
values	O
.	O
</s>
<s>
The	O
concern	O
with	O
Bluetooth-based	O
solutions	O
is	O
that	O
the	O
smartphone	O
will	O
continuously	O
emit	O
an	O
RF	O
signal	O
every	O
200ms	O
,	O
which	O
can	O
be	O
spied	O
on	O
.	O
</s>
<s>
On	O
the	O
other	O
hand	O
,	O
digital	B-Protocol
contact	I-Protocol
tracing	I-Protocol
solutions	O
that	O
force	O
users	O
to	O
release	O
their	O
location	O
trails	O
to	O
a	O
central	O
system	O
without	O
encryption	O
can	O
lead	O
to	O
privacy	O
problems	O
.	O
</s>
<s>
Currently	O
,	O
NOVID	O
,	O
which	O
is	O
the	O
only	O
digital	B-Protocol
contact	I-Protocol
tracing	I-Protocol
app	O
with	O
sub-meter	O
contact	O
tracing	O
accuracy	O
,	O
primarily	O
uses	O
Ultrasound	O
.	O
</s>
<s>
One	O
of	O
the	O
largest	O
privacy	O
concerns	O
raised	O
about	O
protocols	O
such	O
as	O
BlueTrace	B-Protocol
or	O
PEPP-PT	B-Protocol
is	O
the	O
usage	O
of	O
centralised	O
report	O
processing	O
.	O
</s>
<s>
Protocols	O
using	O
this	O
approach	O
,	O
such	O
as	O
TCN	B-Protocol
and	O
DP-3T	B-Protocol
,	O
have	O
the	O
client	O
upload	O
a	O
number	O
from	O
which	O
encounter	O
tokens	O
can	O
be	O
derived	O
by	O
individual	O
devices	O
.	O
</s>
<s>
There	O
may	O
,	O
however	O
,	O
still	O
be	O
incidental	O
leakage	O
of	O
static	O
identifiers	O
,	O
such	O
as	O
was	O
the	O
case	O
on	O
the	O
BlueTrace	B-Protocol
apps	O
TraceTogether	B-Application
and	O
COVIDSafe	B-Application
before	O
they	O
were	O
patched	O
.	O
</s>
<s>
Centralized	O
protocols	O
such	O
as	O
BlueTrace	B-Protocol
issue	O
Temporary	O
IDs	O
from	O
the	O
central	O
reporting	O
server	O
,	O
where	O
they	O
are	O
generated	O
by	O
encrypting	O
a	O
static	O
User	O
ID	O
with	O
a	O
secret	O
key	O
only	O
known	O
to	O
the	O
health	O
authority	O
.	O
</s>
<s>
Alternatively	O
,	O
anonymous	O
decentralized	O
protocols	O
such	O
as	O
TCN	B-Protocol
and	O
DP-3T	B-Protocol
have	O
the	O
clients	O
deterministically	O
generate	O
the	O
IDs	O
from	O
a	O
secret	O
key	O
only	O
known	O
to	O
the	O
client	O
.	O
</s>
<s>
NameArchitectureAuthor/promoterLicenceHomepageRefPan	O
-European	O
Privacy-Preserving	O
Proximity	O
Tracing	O
(	O
PEPP-PT	B-Protocol
)	O
projectCentral	O
log	O
processing	O
,	O
Ephemeral	O
IDsFraunhofer	O
Institute	O
for	O
Telecommunications	O
,	O
Robert	O
Koch	O
Institute	O
,	O
Technical	O
University	O
of	O
Berlin	O
,	O
TU	O
Dresden	O
,	O
University	O
of	O
Erfurt	O
,	O
Vodafone	O
Germany	O
,	O
French	O
Institute	O
for	O
Research	O
in	O
Computer	O
Science	O
and	O
Automation	O
(	O
Inria	O
)	O
multiple	O
protocols	O
,	O
closed	O
source	O
,	O
private	O
specificationshttps://www.pepp-pt.org/	O
Exposure	O
NotificationClient	O
log	O
processing	O
,	O
Ephemeral	O
IDsGoogle	O
,	O
Apple	O
Inc.public	O
specificationhttps://www.apple.com/covid19/contacttracinghttps://www.google.com/covid19/exposurenotifications/Decentralized	O
Privacy-Preserving	O
Proximity	O
Tracing	O
(	O
DP-3T	B-Protocol
)	O
Client	O
log	O
processing	O
,	O
</s>
<s>
Ephemeral	O
IDsEPFL	O
,	O
ETHZ	O
,	O
KU	O
Leuven	O
,	O
TU	O
Delft	O
,	O
University	O
College	O
London	O
,	O
CISPA	O
,	O
University	O
of	O
Oxford	O
,	O
University	O
of	O
Torino	O
/	O
ISI	O
Foundationpublicly-developed	O
Apache	O
2.0	O
reference	O
implementation	O
,	O
MPL	B-License
2.0	I-License
iOS/Android	O
code.https://github.com/DP	O
-3TBlueTrace	O
/	O
OpenTraceCentral	O
log	O
processing	O
,	O
</s>
<s>
Ephemeral	O
IDsCovid	O
Watch	O
,	O
CoEpi	O
,	O
ITO	O
,	O
Commons	O
Project	O
,	O
Zcash	B-Protocol
Foundation	O
,	O
Openminedpublicly	O
developed	O
,	O
Apache	B-Application
License	I-Application
codehttps://github.com/TCNCoalition/TCNWhisper	O
Tracing	O
Protocol	O
(	O
Coalition	O
App	O
)	O
Client	O
log	O
processing	O
,	O
Ephemeral	O
IDsNodle	O
,	O
Berkeley	O
,	O
California	O
,	O
TCN	B-Protocol
Coalition	O
,	O
French	O
Institute	O
for	O
Research	O
in	O
Computer	O
Science	O
and	O
Automation	O
(	O
Inria	O
)	O
GPL	O
3https://www.coalitionnetwork.org/Privacy	O
Automated	O
Contact	O
Tracing	O
(	O
East	O
Coast	O
PACT	O
)	O
Client	O
log	O
processing	O
,	O
</s>
<s>
During	O
the	O
currently	O
unfolding	O
COVID-19	O
pandemic	O
,	O
reactions	O
to	O
digital	B-Protocol
contact	I-Protocol
tracing	I-Protocol
applications	O
worldwide	O
have	O
been	O
drastic	O
and	O
often	O
polarized	O
,	O
especially	O
in	O
European	O
countries	O
.	O
</s>
<s>
Despite	O
holding	O
the	O
promise	O
to	O
drastically	O
reduce	O
contagion	O
and	O
allow	O
for	O
a	O
relaxation	O
of	O
social	O
distancing	O
measures	O
,	O
digital	B-Protocol
contact	I-Protocol
tracing	I-Protocol
applications	O
have	O
been	O
criticized	O
by	O
academia	O
and	O
publics	O
alike	O
.	O
</s>
<s>
NY	O
State	O
Senate	O
Bill	O
S-8448D	O
,	O
which	O
passed	O
in	O
the	O
Senate	O
in	O
July	O
2020	O
,	O
calls	O
for	O
Independent	O
Audit	O
of	O
Digital	B-Protocol
Contact	I-Protocol
Tracing	I-Protocol
.	O
</s>
<s>
Voluntary	O
adoption	O
of	O
digital	B-Protocol
contact	I-Protocol
tracing	I-Protocol
has	O
fallen	O
short	O
of	O
some	O
estimated	O
thresholds	O
for	O
efficacy	O
.	O
</s>
<s>
This	O
has	O
been	O
referred	O
to	O
as	O
a	O
"	O
trust-gap	O
"	O
and	O
advocates	O
for	O
digital	B-Protocol
contact	I-Protocol
tracing	I-Protocol
have	O
endeavored	O
to	O
identify	O
ways	O
to	O
bridge	O
the	O
gap	O
.	O
</s>
<s>
The	O
third	O
party	O
auditor	O
examines	O
all	O
details	O
of	O
digital	B-Protocol
contact	I-Protocol
tracing	I-Protocol
in	O
the	O
areas	O
of	O
ethics	O
,	O
trust	O
,	O
privacy	O
,	O
bias	O
and	O
cybersecurity	O
.	O
</s>
<s>
The	O
audit	O
provides	O
oversight	O
,	O
transparency	O
and	O
accountability	O
over	O
the	O
authority	O
providing	O
the	O
digital	B-Protocol
contact	I-Protocol
tracing	I-Protocol
.	O
</s>
<s>
The	O
technical	O
feasibility	O
and	O
necessity	O
of	O
digital	B-Protocol
contact	I-Protocol
tracing	I-Protocol
is	O
currently	O
subject	O
of	O
debate	O
,	O
with	O
its	O
major	O
proponents	O
claiming	O
it	O
to	O
be	O
indispensable	O
to	O
stop	O
the	O
spread	O
of	O
pandemics	O
,	O
as	O
COVID-19	O
,	O
and	O
its	O
opponents	O
raising	O
points	O
on	O
its	O
technical	O
functioning	O
and	O
adoption	O
rate	O
by	O
citizens	O
.	O
</s>
<s>
Indeed	O
,	O
according	O
to	O
a	O
study	O
published	O
in	O
Science	O
,	O
an	O
adoption	O
rate	O
between	O
of	O
around	O
60%	O
of	O
the	O
total	O
population	O
is	O
needed	O
for	O
digital	B-Protocol
contact	I-Protocol
tracing	I-Protocol
applications	O
to	O
be	O
effective	O
.	O
</s>
<s>
Second	O
,	O
the	O
efficacy	O
of	O
using	O
Bluetooth	B-Protocol
technology	I-Protocol
to	O
determine	O
proximity	O
is	O
subject	O
to	O
scrutiny	O
,	O
with	O
critics	O
pointing	O
out	O
that	O
false	O
positives	O
could	O
be	O
reported	O
due	O
to	O
the	O
inaccuracy	O
of	O
the	O
technology	O
.	O
</s>
<s>
Smartphone-based	O
digital	B-Protocol
contact	I-Protocol
tracing	I-Protocol
applications	O
have	O
system	O
requirements	O
such	O
as	O
Android/iOS	O
version	O
,	O
bluetooth	B-Protocol
enabled	O
,	O
gps	O
enabled	O
.	O
</s>
<s>
Smartphones	O
stop	O
receiving	O
software	O
updates	O
a	O
few	O
years	O
after	O
release	O
(	O
2	O
–	O
3	O
years	O
for	O
Android	B-Application
,	O
5	O
years	O
for	O
iOS	B-Application
)	O
.	O
</s>
<s>
Improvements	O
to	O
this	O
ecosystem	O
would	O
benefit	O
the	O
adoption	O
rate	O
of	O
future	O
digital	B-Protocol
contact	I-Protocol
tracing	I-Protocol
applications	O
.	O
</s>
<s>
On	O
privacy	O
,	O
the	O
main	O
problem	O
about	O
digital	B-Protocol
contact	I-Protocol
tracing	I-Protocol
regards	O
type	O
of	O
information	O
which	O
can	O
be	O
collected	O
from	O
each	O
person	O
and	O
the	O
way	O
related	O
data	O
is	O
treated	O
by	O
companies	O
and	O
institutions	O
.	O
</s>
<s>
The	O
possibility	O
that	O
a	O
wide-ranging	O
adoption	O
of	O
digital	B-Protocol
contact	I-Protocol
tracing	I-Protocol
could	O
set	O
a	O
dangerous	O
precedent	O
for	O
surveillance	O
and	O
control	O
has	O
been	O
abundantly	O
treated	O
by	O
media	O
and	O
academia	O
alike	O
.	O
</s>
<s>
Electronic	O
waste	O
may	O
result	O
from	O
the	O
need	O
to	O
purchase	O
a	O
new	O
smartphone	O
to	O
meet	O
the	O
system	O
requirements	O
of	O
smartphone-based	O
digital	B-Protocol
contact	I-Protocol
tracing	I-Protocol
applications	O
.	O
</s>
