<s>
Convergence	B-Protocol
was	O
a	O
proposed	O
strategy	O
for	O
replacing	O
SSL	B-Architecture
certificate	I-Architecture
authorities	I-Architecture
,	O
first	O
put	O
forth	O
by	O
Moxie	O
Marlinspike	O
in	O
August	O
2011	O
while	O
giving	O
a	O
talk	O
titled	O
"	O
SSL	B-Protocol
and	O
the	O
Future	O
of	O
Authenticity	O
"	O
at	O
the	O
Black	O
Hat	O
security	O
conference	O
.	O
</s>
<s>
It	O
was	O
demonstrated	O
with	O
a	O
Firefox	B-Operating_System
addon	I-Operating_System
and	O
a	O
server-side	O
notary	O
daemon	B-Operating_System
.	O
</s>
<s>
In	O
the	O
talk	O
,	O
Marlinspike	O
proposed	O
that	O
all	O
of	O
the	O
current	O
problems	O
with	O
the	O
certificate	B-Architecture
authority	I-Architecture
(	O
CA	O
)	O
system	O
could	O
be	O
reduced	O
to	O
a	O
single	O
missing	O
property	O
,	O
which	O
he	O
called	O
"	O
trust	O
agility	O
"	O
and	O
which	O
Convergence	B-Protocol
aimed	O
to	O
provide	O
.	O
</s>
<s>
As	O
of	O
2013	O
,	O
Marlinspike	O
is	O
focused	O
on	O
an	O
IETF	O
proposal	O
called	O
TACK	O
,	O
which	O
is	O
designed	O
to	O
be	O
an	O
uncontroversial	O
first	O
step	O
that	O
advocates	O
for	O
dynamic	O
certificate	B-Protocol
pinning	I-Protocol
instead	O
of	O
full	O
CA	O
replacement	O
and	O
reduces	O
the	O
number	O
of	O
times	O
a	O
third	O
party	O
needs	O
to	O
be	O
trusted	O
.	O
</s>
<s>
Development	O
of	O
Convergence	B-Protocol
was	O
continued	O
in	O
a	O
"	O
Convergence	B-Protocol
Extra	O
"	O
fork	O
until	O
about	O
2014	O
.	O
</s>
<s>
Convergence	B-Protocol
was	O
based	O
on	O
previous	O
work	O
from	O
the	O
Perspectives	O
Project	O
at	O
Carnegie	O
Mellon	O
University	O
.	O
</s>
<s>
Like	O
Perspectives	O
,	O
Convergence	B-Protocol
authenticated	O
connections	O
by	O
contacting	O
external	O
notaries	O
,	O
but	O
unlike	O
Perspectives	O
,	O
Convergence	B-Protocol
notaries	O
could	O
use	O
a	O
number	O
of	O
different	O
strategies	O
beyond	O
network	O
perspective	O
in	O
order	O
to	O
reach	O
a	O
verdict	O
.	O
</s>
<s>
The	O
purpose	O
of	O
a	O
certificate	B-Architecture
authority	I-Architecture
in	O
the	O
conventional	O
SSL	B-Protocol
system	O
is	O
to	O
vouch	O
for	O
the	O
identity	O
of	O
a	O
site	O
,	O
by	O
checking	O
its	O
SSL	B-Protocol
certificate	O
.	O
</s>
<s>
A	O
single	O
site	O
is	O
vouched	O
for	O
by	O
only	O
a	O
single	O
certificate	B-Architecture
authority	I-Architecture
(	O
CA	O
)	O
,	O
and	O
this	O
CA	O
has	O
to	O
be	O
trusted	O
by	O
the	O
user	O
.	O
</s>
<s>
This	O
happened	O
when	O
major	O
browsers	O
lost	O
trust	O
in	O
the	O
DigiNotar	O
CA	O
and	O
sites	O
registered	O
with	O
this	O
CA	O
had	O
to	O
get	O
new	O
certificate	B-Architecture
authorities	I-Architecture
(	O
see	O
Certificate	B-Architecture
authority	I-Architecture
#CA	O
compromise	O
for	O
more	O
examples	O
of	O
trust	O
breaches	O
)	O
.	O
</s>
<s>
With	O
Convergence	B-Protocol
,	O
however	O
,	O
there	O
was	O
a	O
level	O
of	O
redundancy	O
,	O
and	O
no	B-Architecture
single	I-Architecture
point	I-Architecture
of	I-Architecture
failure	I-Architecture
.	O
</s>
<s>
If	O
the	O
notaries	O
disagreed	O
on	O
whether	O
a	O
site	O
's	O
identity	O
was	O
correct	O
,	O
the	O
user	O
could	O
choose	O
to	O
go	O
with	O
the	O
majority	O
vote	O
,	O
or	O
err	O
on	O
the	O
side	O
of	O
caution	O
and	O
demand	O
that	O
all	O
notaries	O
agree	O
,	O
or	O
be	O
content	O
with	O
a	O
single	O
notary	O
(	O
the	O
voting	O
method	O
was	O
controlled	O
with	O
a	O
setting	O
in	O
the	O
browser	O
addon	B-Operating_System
)	O
.	O
</s>
<s>
If	O
a	O
user	O
chose	O
to	O
distrust	O
a	O
certain	O
notary	O
,	O
a	O
non-malicious	O
site	O
could	O
still	O
be	O
trusted	O
as	O
long	O
as	O
the	O
remaining	O
trusted	O
notaries	O
trusted	O
it	O
;	O
thus	O
there	O
was	O
no	O
longer	O
a	O
single	B-Architecture
point	I-Architecture
of	I-Architecture
failure	I-Architecture
.	O
</s>
<s>
A	O
list	O
of	O
notaries	O
was	O
maintained	O
on	O
the	O
Convergence	B-Protocol
wiki	O
.	O
</s>
<s>
The	O
Monkeysphere	O
Project	O
tries	O
to	O
solve	O
the	O
same	O
problem	O
by	O
using	O
the	O
PGP	B-Application
web	O
of	O
trust	O
model	O
to	O
assess	O
the	O
authenticity	O
of	O
https	O
certificates	O
.	O
</s>
<s>
HTTP	B-Protocol
Public	I-Protocol
Key	I-Protocol
Pinning	I-Protocol
is	O
a	O
security	O
mechanism	O
which	O
allows	O
HTTPS	O
websites	O
to	O
resist	O
impersonation	O
by	O
attackers	O
using	O
mis-issued	O
or	O
otherwise	O
fraudulent	O
certificates	O
.	O
</s>
<s>
Certificate	B-Protocol
Transparency	I-Protocol
is	O
an	O
attempt	O
to	O
solve	O
the	O
problem	O
by	O
verifiable	O
append-only	O
public	O
logs	O
.	O
</s>
