<s>
BlueTrace	B-Protocol
is	O
an	O
open-source	B-License
application	B-Application
protocol	I-Application
that	O
facilitates	O
digital	B-Protocol
contact	I-Protocol
tracing	I-Protocol
of	O
users	O
to	O
stem	O
the	O
spread	O
of	O
the	O
COVID-19	O
pandemic	O
.	O
</s>
<s>
Initially	O
developed	O
by	O
the	O
Singaporean	O
Government	O
,	O
BlueTrace	B-Protocol
powers	O
the	O
contact	O
tracing	O
for	O
the	O
TraceTogether	B-Application
app	O
.	O
</s>
<s>
Australia	O
and	O
the	O
United	O
Arab	O
Emirates	O
have	O
already	O
adopted	O
the	O
protocol	O
in	O
their	O
gov	O
apps	O
,	O
and	O
other	O
countries	O
were	O
considering	O
BlueTrace	B-Protocol
for	O
adoption	O
.	O
</s>
<s>
Preservation	O
of	O
user	O
privacy	O
was	O
one	O
of	O
the	O
core	O
considerations	O
around	O
which	O
BlueTrace	B-Protocol
was	O
designed	O
.	O
</s>
<s>
Contact	O
tracing	O
is	O
done	O
entirely	O
locally	O
on	O
a	O
client	O
device	O
using	O
Bluetooth	B-General_Concept
Low	I-General_Concept
Energy	I-General_Concept
,	O
storing	O
all	O
encounters	O
in	O
a	O
contact	O
history	O
log	O
chronicling	O
encounters	O
for	O
the	O
past	O
21	O
days	O
.	O
</s>
<s>
The	O
DDC	O
component	O
operates	O
on	O
top	O
of	O
the	O
existing	O
Bluetooth	B-General_Concept
Low	I-General_Concept
Energy	I-General_Concept
protocol	O
,	O
defining	O
how	O
two	O
devices	O
acknowledge	O
each	O
other	O
's	O
presence	O
.	O
</s>
<s>
The	O
DRSC	O
component	O
uses	O
HTTPS	B-Protocol
to	O
communicate	O
a	O
timeline	O
of	O
visits	O
to	O
a	O
centralized	O
server	O
owned	O
by	O
a	O
health	O
authority	O
once	O
a	O
user	O
has	O
tested	O
positive	O
for	O
an	O
infection	O
.	O
</s>
<s>
Each	O
app	O
implementing	O
the	O
BlueTrace	B-Protocol
protocol	O
has	O
a	O
corresponding	O
central	O
reporting	O
server	O
operated	O
by	O
a	O
health	O
authority	O
.	O
</s>
<s>
When	O
the	O
user	O
first	O
launches	O
a	O
BlueTrace	B-Protocol
app	O
,	O
they	O
will	O
be	O
asked	O
for	O
their	O
internationally	O
formatted	O
phone	O
number	O
and	O
are	O
assigned	O
a	O
static	O
UserID	O
.	O
</s>
<s>
TempIDs	O
are	O
generated	O
from	O
a	O
user	O
's	O
UserID	O
,	O
the	O
TempID	O
start	O
time	O
,	O
and	O
the	O
TempID	O
expiry	O
time	O
,	O
which	O
is	O
encrypted	O
and	O
turned	O
into	O
a	O
Base64	B-Protocol
encoded	O
string	O
by	O
the	O
server	O
using	O
a	O
secret	O
symmetric	B-Algorithm
encryption	I-Algorithm
key	O
.	O
</s>
<s>
The	O
packet	O
is	O
formed	O
as	O
a	O
JSON	B-General_Concept
file	O
,	O
containing	O
the	O
device	O
's	O
TempID	O
,	O
device	O
model	O
,	O
HAI	O
,	O
and	O
BlueTrace	B-Protocol
protocol	O
version	O
.	O
</s>
<s>
The	O
cooperation	O
between	O
separate	O
health	O
authorities	O
is	O
a	O
core	O
component	O
of	O
the	O
BlueTrace	B-Protocol
protocol	O
,	O
and	O
it	O
is	O
designed	O
such	O
that	O
multiple	O
authorities	O
can	O
work	O
together	O
without	O
revealing	O
personal	O
information	O
to	O
foreign	O
authorities	O
with	O
which	O
a	O
user	O
is	O
not	O
registered	O
.	O
</s>
<s>
The	O
PseudoID	O
is	O
a	O
salted	O
cryptographic	B-Algorithm
hash	I-Algorithm
of	O
the	O
UserID	O
,	O
designed	O
to	O
allow	O
foreign	O
health	O
authorities	O
to	O
perform	O
statistical	O
analysis	O
on	O
contact	O
logs	O
and	O
communicate	O
about	O
a	O
specific	O
user	O
without	O
revealing	O
unnecessary	O
personal	O
information	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>
OpenTrace	O
is	O
the	O
open-source	B-License
reference	O
implementation	O
of	O
BlueTrace	B-Protocol
released	O
under	O
the	O
GPL-3.0	O
license	O
.	O
</s>
<s>
The	O
DRSC	O
side	O
of	O
the	O
protocol	O
is	O
implemented	O
using	O
the	O
Firebase	B-General_Concept
platform	O
,	O
using	O
Firebase	B-General_Concept
functions	O
,	O
a	O
serverless	B-General_Concept
computing	I-General_Concept
framework	O
,	O
for	O
all	O
client	O
calls	O
;	O
and	O
Firebase	B-General_Concept
Secret	O
Manager	O
and	O
Storage	O
for	O
storing	O
the	O
encryption	O
key	O
and	O
contact	O
logs	O
respectively	O
.	O
</s>
<s>
For	O
the	O
app/DDC	O
side	O
of	O
the	O
protocol	O
,	O
a	O
modified	O
version	O
of	O
the	O
TraceTogether	B-Application
app	O
for	O
Android	O
and	O
iOS	O
devices	O
is	O
included	O
.	O
</s>
<s>
COVIDSafe	O
is	O
a	O
digital	B-Protocol
contact	I-Protocol
tracing	I-Protocol
app	O
announced	O
by	O
the	O
Federal	O
Australian	O
Government	O
based	O
on	O
OpenTrace/BlueTrace	O
,	O
announced	O
on	O
14	O
April	O
2020	O
to	O
help	O
combat	O
the	O
ongoing	O
COVID-19	O
pandemic	O
.	O
</s>
