<s>
On	O
April	O
16	O
,	O
2020	O
,	O
Nodle	O
released	O
The	O
Whisper	B-Protocol
Tracing	I-Protocol
Protocol	I-Protocol
white	O
paper	O
and	O
the	O
Coalition	O
App	O
on	O
Android	B-Application
.	O
</s>
<s>
The	O
protocol	O
is	O
intended	O
to	O
be	O
a	O
privacy	O
first	O
Digital	B-Protocol
contact	I-Protocol
tracing	I-Protocol
tool	O
developed	O
for	O
the	O
2020	O
COVID-19	O
pandemic	O
.	O
</s>
<s>
The	O
deployed	O
system	O
uses	O
Bluetooth	B-General_Concept
LE	I-General_Concept
to	O
exchange	O
rotating	O
public	O
keys	O
between	O
two	O
users	O
.	O
</s>
<s>
The	O
protocol	O
leverages	O
a	O
keyed	O
hash	O
function	O
using	O
160	O
Bit	O
BLAKE	B-Algorithm
2	O
(	O
hash	O
function	O
)	O
to	O
generate	O
user	O
keys	O
:	O
</s>
<s>
Seed	O
:	O
Generated	O
and	O
stored	O
locally	O
on	O
the	O
smartphone	B-Application
or	O
user	O
hardware	O
.	O
</s>
<s>
This	O
key	O
is	O
included	O
in	O
the	O
bluetooth	B-Protocol
data	O
packet	O
.	O
</s>
<s>
Smartphones	B-Application
running	O
the	O
protocol	O
record	O
"	O
proximity	O
events	O
"	O
which	O
may	O
include	O
the	O
Temporary	O
ID	O
of	O
the	O
user	O
in	O
contact	O
,	O
time	O
,	O
signal	O
strength	O
,	O
location	O
,	O
and	O
other	O
metadata	O
.	O
</s>
<s>
A	O
key	O
difference	O
with	O
other	O
Digital	B-Protocol
contact	I-Protocol
tracing	I-Protocol
tools	O
is	O
that	O
the	O
Contacttracing	O
happens	O
locally	O
on	O
the	O
phone	O
,	O
meaning	O
that	O
the	O
system	O
does	O
not	O
need	O
to	O
transmit	O
location	O
,	O
or	O
all	O
of	O
the	O
user	O
's	O
proximity	O
events	O
to	O
a	O
server	O
.	O
</s>
