<s>
Hypertext	B-Protocol
Transfer	I-Protocol
Protocol	I-Protocol
Secure	I-Protocol
(	O
HTTPS	B-Protocol
)	O
is	O
an	O
extension	O
of	O
the	O
Hypertext	B-Protocol
Transfer	I-Protocol
Protocol	I-Protocol
(	O
HTTP	B-Protocol
)	O
.	O
</s>
<s>
It	O
uses	O
encryption	O
for	O
secure	O
communication	O
over	O
a	O
computer	B-Architecture
network	I-Architecture
,	O
and	O
is	O
widely	O
used	O
on	O
the	O
Internet	O
.	O
</s>
<s>
In	O
HTTPS	B-Protocol
,	O
the	O
communication	O
protocol	O
is	O
encrypted	O
using	O
Transport	B-Protocol
Layer	I-Protocol
Security	I-Protocol
(	O
TLS	B-Protocol
)	O
or	O
,	O
formerly	O
,	O
Secure	B-Protocol
Sockets	I-Protocol
Layer	I-Protocol
(	O
SSL	B-Protocol
)	O
.	O
</s>
<s>
The	O
protocol	O
is	O
therefore	O
also	O
referred	O
to	O
as	O
HTTP	B-Protocol
over	I-Protocol
TLS	I-Protocol
,	O
or	O
HTTP	B-Protocol
over	I-Protocol
SSL	I-Protocol
.	O
</s>
<s>
The	O
principal	O
motivations	O
for	O
HTTPS	B-Protocol
are	O
authentication	O
of	O
the	O
accessed	O
website	O
and	O
protection	O
of	O
the	O
privacy	O
and	O
integrity	O
of	O
the	O
exchanged	O
data	O
while	O
it	O
is	O
in	O
transit	O
.	O
</s>
<s>
It	O
protects	O
against	O
man-in-the-middle	O
attacks	O
,	O
and	O
the	O
bidirectional	O
block	B-Algorithm
cipher	I-Algorithm
encryption	I-Algorithm
of	O
communications	O
between	O
a	O
client	O
and	O
server	B-Application
protects	O
the	O
communications	O
against	O
eavesdropping	O
and	O
tampering	O
.	O
</s>
<s>
The	O
authentication	O
aspect	O
of	O
HTTPS	B-Protocol
requires	O
a	O
trusted	O
third	O
party	O
to	O
sign	O
server-side	O
digital	O
certificates	O
.	O
</s>
<s>
This	O
was	O
historically	O
an	O
expensive	O
operation	O
,	O
which	O
meant	O
fully	O
authenticated	O
HTTPS	B-Protocol
connections	I-Protocol
were	O
usually	O
found	O
only	O
on	O
secured	O
payment	O
transaction	O
services	O
and	O
other	O
secured	O
corporate	O
information	O
systems	O
on	O
the	O
World	O
Wide	O
Web	O
.	O
</s>
<s>
In	O
2016	O
,	O
a	O
campaign	O
by	O
the	O
Electronic	O
Frontier	O
Foundation	O
with	O
the	O
support	O
of	O
web	B-Application
browser	I-Application
developers	O
led	O
to	O
the	O
protocol	O
becoming	O
more	O
prevalent	O
.	O
</s>
<s>
HTTPS	B-Protocol
is	O
now	O
used	O
more	O
often	O
by	O
web	O
users	O
than	O
the	O
original	O
,	O
non-secure	O
HTTP	O
,	O
primarily	O
to	O
protect	O
page	O
authenticity	O
on	O
all	O
types	O
of	O
websites	O
,	O
secure	O
accounts	O
,	O
and	O
keep	O
user	O
communications	O
,	O
identity	O
,	O
and	O
web	O
browsing	O
private	O
.	O
</s>
<s>
The	O
Uniform	B-Protocol
Resource	I-Protocol
Identifier	I-Protocol
(	O
URI	B-Protocol
)	O
scheme	O
HTTPS	B-Protocol
has	O
identical	O
usage	O
syntax	O
to	O
the	O
HTTP	B-Protocol
scheme	O
.	O
</s>
<s>
However	O
,	O
HTTPS	B-Protocol
signals	O
the	O
browser	B-Application
to	O
use	O
an	O
added	O
encryption	O
layer	O
of	O
SSL/TLS	B-Protocol
to	O
protect	O
the	O
traffic	O
.	O
</s>
<s>
SSL/TLS	B-Protocol
is	O
especially	O
suited	O
for	O
HTTP	B-Protocol
,	O
since	O
it	O
can	O
provide	O
some	O
protection	O
even	O
if	O
only	O
one	O
side	O
of	O
the	O
communication	O
is	O
authenticated	O
.	O
</s>
<s>
This	O
is	O
the	O
case	O
with	O
HTTP	B-Protocol
transactions	O
over	O
the	O
Internet	O
,	O
where	O
typically	O
only	O
the	O
server	B-Application
is	O
authenticated	O
(	O
by	O
the	O
client	O
examining	O
the	O
server	B-Application
's	O
certificate	O
)	O
.	O
</s>
<s>
HTTPS	B-Protocol
creates	O
a	O
secure	O
channel	O
over	O
an	O
insecure	O
network	O
.	O
</s>
<s>
This	O
ensures	O
reasonable	O
protection	O
from	O
eavesdroppers	O
and	O
man-in-the-middle	O
attacks	O
,	O
provided	O
that	O
adequate	O
cipher	B-Protocol
suites	I-Protocol
are	O
used	O
and	O
that	O
the	O
server	B-Application
certificate	O
is	O
verified	O
and	O
trusted	O
.	O
</s>
<s>
Because	O
HTTPS	B-Protocol
piggybacks	O
HTTP	B-Protocol
entirely	O
on	O
top	O
of	O
TLS	B-Protocol
,	O
the	O
entirety	O
of	O
the	O
underlying	O
HTTP	B-Protocol
protocol	I-Protocol
can	O
be	O
encrypted	O
.	O
</s>
<s>
This	O
includes	O
the	O
request	O
's	O
URL	O
,	O
query	O
parameters	O
,	O
headers	O
,	O
and	O
cookies	B-Application
(	O
which	O
often	O
contain	O
identifying	O
information	O
about	O
the	O
user	O
)	O
.	O
</s>
<s>
However	O
,	O
because	O
website	O
addresses	O
and	O
port	B-Protocol
numbers	I-Protocol
are	O
necessarily	O
part	O
of	O
the	O
underlying	O
TCP/IP	B-Protocol
protocols	I-Protocol
,	O
HTTPS	B-Protocol
cannot	O
protect	O
their	O
disclosure	O
.	O
</s>
<s>
In	O
practice	O
this	O
means	O
that	O
even	O
on	O
a	O
correctly	O
configured	O
web	B-Application
server	I-Application
,	O
eavesdroppers	O
can	O
infer	O
the	O
IP	O
address	O
and	O
port	B-Protocol
number	I-Protocol
of	O
the	O
web	B-Application
server	I-Application
,	O
and	O
sometimes	O
even	O
the	O
domain	O
name	O
(	O
e.g.	O
</s>
<s>
Web	B-Application
browsers	I-Application
know	O
how	O
to	O
trust	O
HTTPS	B-Protocol
websites	I-Protocol
based	O
on	O
certificate	B-Architecture
authorities	I-Architecture
that	O
come	O
pre-installed	O
in	O
their	O
software	O
.	O
</s>
<s>
Certificate	B-Architecture
authorities	I-Architecture
are	O
in	O
this	O
way	O
being	O
trusted	O
by	O
web	B-Application
browser	I-Application
creators	O
to	O
provide	O
valid	O
certificates	O
.	O
</s>
<s>
Therefore	O
,	O
a	O
user	O
should	O
trust	O
an	O
HTTPS	B-Protocol
connection	I-Protocol
to	O
a	O
website	O
if	O
and	O
only	O
if	O
all	O
of	O
the	O
following	O
are	O
true	O
:	O
</s>
<s>
The	O
user	O
trusts	O
that	O
their	O
device	O
,	O
hosting	O
the	O
browser	B-Application
and	O
the	O
method	O
to	O
get	O
the	O
browser	B-Application
itself	O
,	O
is	O
not	O
compromised	O
(	O
i.e.	O
</s>
<s>
The	O
user	O
trusts	O
that	O
the	O
browser	B-Application
software	O
correctly	O
implements	O
HTTPS	B-Protocol
with	O
correctly	O
pre-installed	O
certificate	B-Architecture
authorities	I-Architecture
.	O
</s>
<s>
The	O
user	O
trusts	O
the	O
certificate	B-Architecture
authority	I-Architecture
to	O
vouch	O
only	O
for	O
legitimate	O
websites	O
(	O
i.e.	O
</s>
<s>
the	O
certificate	B-Architecture
authority	I-Architecture
is	O
not	O
compromised	O
and	O
there	O
is	O
no	O
mis-issuance	O
of	O
certificates	O
)	O
.	O
</s>
<s>
The	O
certificate	O
correctly	O
identifies	O
the	O
website	O
(	O
e.g.	O
,	O
when	O
the	O
browser	B-Application
visits	O
""	O
,	O
the	O
received	O
certificate	O
is	O
properly	O
for	O
"	O
example.com	O
 "	O
and	O
not	O
some	O
other	O
entity	O
)	O
.	O
</s>
<s>
The	O
user	O
trusts	O
that	O
the	O
protocol	O
's	O
encryption	O
layer	O
(	O
SSL/TLS	B-Protocol
)	O
is	O
sufficiently	O
secure	O
against	O
eavesdroppers	O
.	O
</s>
<s>
HTTPS	B-Protocol
is	O
especially	O
important	O
over	O
insecure	O
networks	O
and	O
networks	O
that	O
may	O
be	O
subject	O
to	O
tampering	O
.	O
</s>
<s>
Insecure	O
networks	O
,	O
such	O
as	O
public	B-Application
Wi-Fi	O
access	O
points	O
,	O
allow	O
anyone	O
on	O
the	O
same	O
local	O
network	O
to	O
packet-sniff	B-Protocol
and	O
discover	O
sensitive	O
information	O
not	O
protected	O
by	O
HTTPS	B-Protocol
.	I-Protocol
</s>
<s>
Additionally	O
,	O
some	O
free-to-use	O
and	O
paid	O
WLAN	B-Architecture
networks	O
have	O
been	O
observed	O
tampering	O
with	O
webpages	O
by	O
engaging	O
in	O
packet	B-Protocol
injection	I-Protocol
in	O
order	O
to	O
serve	O
their	O
own	O
ads	O
on	O
other	O
websites	O
.	O
</s>
<s>
HTTPS	B-Protocol
is	O
also	O
important	O
for	O
connections	O
over	O
the	O
Tor	B-Application
network	I-Application
,	O
as	O
malicious	O
Tor	B-Application
nodes	I-Application
could	O
otherwise	O
damage	O
or	O
alter	O
the	O
contents	O
passing	O
through	O
them	O
in	O
an	O
insecure	O
fashion	O
and	O
inject	O
malware	O
into	O
the	O
connection	O
.	O
</s>
<s>
This	O
is	O
one	O
reason	O
why	O
the	O
Electronic	O
Frontier	O
Foundation	O
and	O
the	O
Tor	B-Application
Project	I-Application
started	O
the	O
development	O
of	O
HTTPS	B-Operating_System
Everywhere	I-Operating_System
,	O
which	O
is	O
included	O
in	O
Tor	B-Application
Browser	B-Application
.	O
</s>
<s>
As	O
more	O
information	O
is	O
revealed	O
about	O
global	O
mass	O
surveillance	O
and	O
criminals	O
stealing	O
personal	O
information	O
,	O
the	O
use	O
of	O
HTTPS	B-Protocol
security	O
on	O
all	O
websites	O
is	O
becoming	O
increasingly	O
important	O
regardless	O
of	O
the	O
type	O
of	O
Internet	O
connection	O
being	O
used	O
.	O
</s>
<s>
Deploying	O
HTTPS	B-Protocol
also	O
allows	O
the	O
use	O
of	O
HTTP/2	B-Protocol
and	O
HTTP/3	B-Protocol
(	O
and	O
their	O
predecessors	O
SPDY	B-Protocol
and	O
QUIC	B-Protocol
)	O
,	O
which	O
are	O
new	O
HTTP	B-Protocol
versions	O
designed	O
to	O
reduce	O
page	O
load	O
times	O
,	O
size	O
,	O
and	O
latency	O
.	O
</s>
<s>
It	O
is	O
recommended	O
to	O
use	O
HTTP	B-Protocol
Strict	I-Protocol
Transport	I-Protocol
Security	I-Protocol
(	O
HSTS	B-Protocol
)	O
with	O
HTTPS	B-Protocol
to	O
protect	O
users	O
from	O
man-in-the-middle	O
attacks	O
,	O
especially	O
SSL	B-Protocol
stripping	O
.	O
</s>
<s>
HTTPS	B-Protocol
should	O
not	O
be	O
confused	O
with	O
the	O
seldom-used	O
Secure	B-Protocol
HTTP	I-Protocol
(	O
S-HTTP	B-Protocol
)	O
specified	O
in	O
RFC	O
2660	O
.	O
</s>
<s>
,	O
33.2	O
%	O
of	O
Alexa	O
top	O
1,000,000	O
websites	O
use	O
HTTPS	B-Protocol
as	O
default	O
,	O
57.1	O
%	O
of	O
the	O
Internet	O
's	O
137,971	O
most	O
popular	O
websites	O
have	O
a	O
secure	O
implementation	O
of	O
HTTPS	B-Protocol
,	O
and	O
70%	O
of	O
page	O
loads	O
(	O
measured	O
by	O
Firefox	B-Application
Telemetry	O
)	O
use	O
HTTPS	B-Protocol
.	I-Protocol
</s>
<s>
However	O
despite	O
TLS	B-Protocol
1.3	O
’	O
s	O
release	O
in	O
2018	O
,	O
adoption	O
has	O
been	O
slow	O
,	O
with	O
many	O
still	O
remain	O
on	O
the	O
older	O
TLS	B-Protocol
1.2	O
protocol	O
.	O
</s>
<s>
Most	O
browsers	B-Application
display	O
a	O
warning	O
if	O
they	O
receive	O
an	O
invalid	O
certificate	O
.	O
</s>
<s>
Older	O
browsers	B-Application
,	O
when	O
connecting	O
to	O
a	O
site	O
with	O
an	O
invalid	O
certificate	O
,	O
would	O
present	O
the	O
user	O
with	O
a	O
dialog	O
box	O
asking	O
whether	O
they	O
wanted	O
to	O
continue	O
.	O
</s>
<s>
Newer	O
browsers	B-Application
display	O
a	O
warning	O
across	O
the	O
entire	O
window	O
.	O
</s>
<s>
Newer	O
browsers	B-Application
also	O
prominently	O
display	O
the	O
site	O
's	O
security	O
information	O
in	O
the	O
address	O
bar	O
.	O
</s>
<s>
Extended	B-Application
validation	I-Application
certificates	I-Application
show	O
the	O
legal	O
entity	O
on	O
the	O
certificate	O
information	O
.	O
</s>
<s>
Most	O
browsers	B-Application
also	O
display	O
a	O
warning	O
to	O
the	O
user	O
when	O
visiting	O
a	O
site	O
that	O
contains	O
a	O
mixture	O
of	O
encrypted	O
and	O
unencrypted	O
content	O
.	O
</s>
<s>
Additionally	O
,	O
many	O
web	B-Protocol
filters	I-Protocol
return	O
a	O
security	O
warning	O
when	O
visiting	O
prohibited	O
websites	O
.	O
</s>
<s>
The	O
Electronic	O
Frontier	O
Foundation	O
,	O
opining	O
that	O
"	O
In	O
an	O
ideal	O
world	O
,	O
every	O
web	O
request	O
could	O
be	O
defaulted	O
to	O
HTTPS	B-Protocol
"	O
,	O
has	O
provided	O
an	O
add-on	O
called	O
HTTPS	B-Operating_System
Everywhere	I-Operating_System
for	O
Mozilla	B-Application
Firefox	I-Application
,	O
Google	B-Application
Chrome	I-Application
,	O
Chromium	B-Language
,	O
and	O
Android	B-Application
,	O
which	O
enables	O
HTTPS	B-Protocol
by	O
default	O
for	O
hundreds	O
of	O
frequently	O
used	O
websites	O
.	O
</s>
<s>
Forcing	O
a	O
web	B-Application
browser	I-Application
to	O
load	O
only	O
HTTPS	B-Protocol
content	O
has	O
been	O
supported	O
in	O
Firefox	B-Application
starting	O
in	O
version	O
83	O
.	O
</s>
<s>
Starting	O
in	O
version	O
94	O
,	O
Google	B-Application
Chrome	I-Application
is	O
able	O
to	O
"	O
always	O
use	O
secure	O
connections	O
"	O
if	O
toggled	O
in	O
the	O
browser	B-Application
's	O
settings	O
.	O
</s>
<s>
The	O
security	O
of	O
HTTPS	B-Protocol
is	O
that	O
of	O
the	O
underlying	O
TLS	B-Protocol
,	O
which	O
typically	O
uses	O
long-term	O
public	B-Application
and	O
private	B-Application
keys	I-Application
to	O
generate	O
a	O
short-term	O
session	O
key	O
,	O
which	O
is	O
then	O
used	O
to	O
encrypt	O
the	O
data	O
flow	O
between	O
the	O
client	O
and	O
the	O
server	B-Application
.	O
</s>
<s>
X.509	O
certificates	O
are	O
used	O
to	O
authenticate	O
the	O
server	B-Application
(	O
and	O
sometimes	O
the	O
client	O
as	O
well	O
)	O
.	O
</s>
<s>
As	O
a	O
consequence	O
,	O
certificate	B-Architecture
authorities	I-Architecture
and	O
public	B-Application
key	I-Application
certificates	O
are	O
necessary	O
to	O
verify	O
the	O
relation	O
between	O
the	O
certificate	O
and	O
its	O
owner	O
,	O
as	O
well	O
as	O
to	O
generate	O
,	O
sign	O
,	O
and	O
administer	O
the	O
validity	O
of	O
certificates	O
.	O
</s>
<s>
While	O
this	O
can	O
be	O
more	O
beneficial	O
than	O
verifying	O
the	O
identities	O
via	O
a	O
web	O
of	O
trust	O
,	O
the	O
2013	O
mass	O
surveillance	O
disclosures	O
drew	O
attention	O
to	O
certificate	B-Architecture
authorities	I-Architecture
as	O
a	O
potential	O
weak	O
point	O
allowing	O
man-in-the-middle	O
attacks	O
.	O
</s>
<s>
Not	O
all	O
web	B-Application
servers	I-Application
provide	O
forward	O
secrecy	O
.	O
</s>
<s>
For	O
HTTPS	B-Protocol
to	O
be	O
effective	O
,	O
a	O
site	O
must	O
be	O
completely	O
hosted	O
over	O
HTTPS	B-Protocol
.	I-Protocol
</s>
<s>
If	O
some	O
of	O
the	O
site	O
's	O
contents	O
are	O
loaded	O
over	O
HTTP	B-Protocol
(	O
scripts	O
or	O
images	O
,	O
for	O
example	O
)	O
,	O
or	O
if	O
only	O
a	O
certain	O
page	O
that	O
contains	O
sensitive	O
information	O
,	O
such	O
as	O
a	O
log-in	O
page	O
,	O
is	O
loaded	O
over	O
HTTPS	B-Protocol
while	O
the	O
rest	O
of	O
the	O
site	O
is	O
loaded	O
over	O
plain	O
HTTP	B-Protocol
,	O
the	O
user	O
will	O
be	O
vulnerable	O
to	O
attacks	O
and	O
surveillance	O
.	O
</s>
<s>
Additionally	O
,	O
cookies	B-Application
on	O
a	O
site	O
served	O
through	O
HTTPS	B-Protocol
must	O
have	O
the	O
secure	B-Application
attribute	I-Application
enabled	O
.	O
</s>
<s>
On	O
a	O
site	O
that	O
has	O
sensitive	O
information	O
on	O
it	O
,	O
the	O
user	O
and	O
the	O
session	O
will	O
get	O
exposed	O
every	O
time	O
that	O
site	O
is	O
accessed	O
with	O
HTTP	B-Protocol
instead	O
of	O
HTTPS	B-Protocol
.	I-Protocol
</s>
<s>
HTTPS	B-Protocol
URLs	I-Protocol
begin	O
with	O
""	O
and	O
use	O
port	B-Protocol
443	I-Protocol
by	O
default	O
,	O
whereas	O
,	O
HTTP	B-Protocol
URLs	O
begin	O
with	O
""	O
and	O
use	O
port	B-Protocol
80	O
by	O
default	O
.	O
</s>
<s>
HTTP	B-Protocol
is	O
not	O
encrypted	O
and	O
thus	O
is	O
vulnerable	O
to	O
man-in-the-middle	O
and	O
eavesdropping	O
attacks	O
,	O
which	O
can	O
let	O
attackers	O
gain	O
access	O
to	O
website	O
accounts	O
and	O
sensitive	O
information	O
,	O
and	O
modify	O
webpages	O
to	O
inject	O
malware	O
or	O
advertisements	O
.	O
</s>
<s>
HTTPS	B-Protocol
is	O
designed	O
to	O
withstand	O
such	O
attacks	O
and	O
is	O
considered	O
secure	O
against	O
them	O
(	O
with	O
the	O
exception	O
of	O
HTTPS	B-Protocol
implementations	O
that	O
use	O
deprecated	O
versions	O
of	O
SSL	B-Protocol
)	O
.	O
</s>
<s>
HTTP	B-Protocol
operates	O
at	O
the	O
highest	O
layer	O
of	O
the	O
TCP/IP	B-Protocol
model	I-Protocol
—	O
the	O
application	B-Application
layer	I-Application
;	O
as	O
does	O
the	O
TLS	B-Protocol
security	O
protocol	O
(	O
operating	O
as	O
a	O
lower	O
sublayer	O
of	O
the	O
same	O
layer	O
)	O
,	O
which	O
encrypts	O
an	O
HTTP	B-Protocol
message	O
prior	O
to	O
transmission	O
and	O
decrypts	O
a	O
message	O
upon	O
arrival	O
.	O
</s>
<s>
Strictly	O
speaking	O
,	O
HTTPS	B-Protocol
is	O
not	O
a	O
separate	O
protocol	O
,	O
but	O
refers	O
to	O
the	O
use	O
of	O
ordinary	O
HTTP	B-Protocol
over	O
an	O
encrypted	O
SSL/TLS	B-Protocol
connection	O
.	O
</s>
<s>
HTTPS	B-Protocol
encrypts	O
all	O
message	O
contents	O
,	O
including	O
the	O
HTTP	B-Protocol
headers	O
and	O
the	O
request/response	O
data	O
.	O
</s>
<s>
To	O
prepare	O
a	O
web	B-Application
server	I-Application
to	O
accept	O
HTTPS	B-Protocol
connections	I-Protocol
,	O
the	O
administrator	O
must	O
create	O
a	O
public	B-Application
key	I-Application
certificate	O
for	O
the	O
web	B-Application
server	I-Application
.	O
</s>
<s>
This	O
certificate	O
must	O
be	O
signed	O
by	O
a	O
trusted	O
certificate	B-Architecture
authority	I-Architecture
for	O
the	O
web	B-Application
browser	I-Application
to	O
accept	O
it	O
without	O
warning	O
.	O
</s>
<s>
The	O
authority	O
certifies	O
that	O
the	O
certificate	O
holder	O
is	O
the	O
operator	O
of	O
the	O
web	B-Application
server	I-Application
that	O
presents	O
it	O
.	O
</s>
<s>
Web	B-Application
browsers	I-Application
are	O
generally	O
distributed	O
with	O
a	O
list	O
of	O
signing	B-Protocol
certificates	I-Protocol
of	I-Protocol
major	I-Protocol
certificate	I-Protocol
authorities	I-Protocol
so	O
that	O
they	O
can	O
verify	O
certificates	O
signed	O
by	O
them	O
.	O
</s>
<s>
A	O
number	O
of	O
commercial	O
certificate	B-Architecture
authorities	I-Architecture
exist	O
,	O
offering	O
paid-for	O
SSL/TLS	B-Protocol
certificates	O
of	O
a	O
number	O
of	O
types	O
,	O
including	O
Extended	B-Application
Validation	I-Application
Certificates	I-Application
.	O
</s>
<s>
Let	B-Application
's	I-Application
Encrypt	I-Application
,	O
launched	O
in	O
April	O
2016	O
,	O
provides	O
free	O
and	O
automated	O
service	O
that	O
delivers	O
basic	O
SSL/TLS	B-Protocol
certificates	O
to	O
websites	O
.	O
</s>
<s>
According	O
to	O
the	O
Electronic	O
Frontier	O
Foundation	O
,	O
Let	B-Application
's	I-Application
Encrypt	I-Application
will	O
make	O
switching	O
from	O
HTTP	B-Protocol
to	O
HTTPS	B-Protocol
"	O
as	O
easy	O
as	O
issuing	O
one	O
command	O
,	O
or	O
clicking	O
one	O
button.	O
"	O
</s>
<s>
The	O
majority	O
of	O
web	O
hosts	O
and	O
cloud	O
providers	O
now	O
leverage	O
Let	B-Application
's	I-Application
Encrypt	I-Application
,	O
providing	O
free	O
certificates	O
to	O
their	O
customers	O
.	O
</s>
<s>
The	O
system	O
can	O
also	O
be	O
used	O
for	O
client	O
authentication	O
in	O
order	O
to	O
limit	O
access	O
to	O
a	O
web	B-Application
server	I-Application
to	O
authorized	O
users	O
.	O
</s>
<s>
To	O
do	O
this	O
,	O
the	O
site	O
administrator	O
typically	O
creates	O
a	O
certificate	O
for	O
each	O
user	O
,	O
which	O
the	O
user	O
loads	O
into	O
their	O
browser	B-Application
.	O
</s>
<s>
Normally	O
,	O
the	O
certificate	O
contains	O
the	O
name	O
and	O
e-mail	O
address	O
of	O
the	O
authorized	O
user	O
and	O
is	O
automatically	O
checked	O
by	O
the	O
server	B-Application
on	O
each	O
connection	O
to	O
verify	O
the	O
user	O
's	O
identity	O
,	O
potentially	O
without	O
even	O
requiring	O
a	O
password	O
.	O
</s>
<s>
Possessing	O
one	O
of	O
the	O
long-term	O
asymmetric	O
secret	O
keys	O
used	O
to	O
establish	O
an	O
HTTPS	B-Protocol
session	O
should	O
not	O
make	O
it	O
easier	O
to	O
derive	O
the	O
short-term	O
session	O
key	O
to	O
then	O
decrypt	O
the	O
conversation	O
,	O
even	O
at	O
a	O
later	O
time	O
.	O
</s>
<s>
Diffie	B-Protocol
–	I-Protocol
Hellman	I-Protocol
key	I-Protocol
exchange	I-Protocol
(	O
DHE	O
)	O
and	O
Elliptic	B-Protocol
curve	I-Protocol
Diffie	I-Protocol
–	I-Protocol
Hellman	I-Protocol
key	I-Protocol
exchange	I-Protocol
(	O
ECDHE	B-Protocol
)	O
are	O
in	O
2013	O
the	O
only	O
schemes	O
known	O
to	O
have	O
that	O
property	O
.	O
</s>
<s>
In	O
2013	O
,	O
only	O
30%	O
of	O
Firefox	B-Application
,	O
Opera	B-Application
,	O
and	O
Chromium	B-Language
Browser	I-Language
sessions	O
used	O
it	O
,	O
and	O
nearly	O
0%	O
of	O
Apple	B-Application
's	I-Application
Safari	I-Application
and	O
Microsoft	B-Application
Internet	I-Application
Explorer	I-Application
sessions	O
.	O
</s>
<s>
TLS	B-Protocol
1.3	O
,	O
published	O
in	O
August	O
2018	O
,	O
dropped	O
support	O
for	O
ciphers	B-Application
without	O
forward	O
secrecy	O
.	O
</s>
<s>
,	O
96.6	O
%	O
of	O
web	B-Application
servers	I-Application
surveyed	O
support	O
some	O
form	O
of	O
forward	O
secrecy	O
,	O
and	O
52.1	O
%	O
will	O
use	O
forward	O
secrecy	O
with	O
most	O
browsers	B-Application
.	O
</s>
<s>
A	O
certificate	O
may	O
be	O
revoked	O
before	O
it	O
expires	O
,	O
for	O
example	O
because	O
the	O
secrecy	O
of	O
the	O
private	B-Application
key	I-Application
has	O
been	O
compromised	O
.	O
</s>
<s>
Newer	O
versions	O
of	O
popular	O
browsers	B-Application
such	O
as	O
Firefox	B-Application
,	O
Opera	B-Application
,	O
and	O
Internet	B-Application
Explorer	I-Application
on	O
Windows	B-Application
Vista	I-Application
implement	O
the	O
Online	B-Protocol
Certificate	I-Protocol
Status	I-Protocol
Protocol	I-Protocol
(	O
OCSP	B-Protocol
)	O
to	O
verify	O
that	O
this	O
is	O
not	O
the	O
case	O
.	O
</s>
<s>
The	O
browser	B-Application
sends	O
the	O
certificate	O
's	O
serial	O
number	O
to	O
the	O
certificate	B-Architecture
authority	I-Architecture
or	O
its	O
delegate	O
via	O
OCSP	B-Protocol
(	O
Online	B-Protocol
Certificate	I-Protocol
Status	I-Protocol
Protocol	I-Protocol
)	O
and	O
the	O
authority	O
responds	O
,	O
telling	O
the	O
browser	B-Application
whether	O
the	O
certificate	O
is	O
still	O
valid	O
or	O
not	O
.	O
</s>
<s>
CRLs	O
are	O
no	O
longer	O
required	O
by	O
the	O
CA/Browser	O
forum	O
,	O
nevertheless	O
,	O
they	O
are	O
still	O
widely	O
used	O
by	O
the	O
CAs	O
.	O
</s>
<s>
SSL	B-Protocol
(	O
Secure	B-Protocol
Sockets	I-Protocol
Layer	I-Protocol
)	O
and	O
TLS	B-Protocol
(	O
Transport	B-Protocol
Layer	I-Protocol
Security	I-Protocol
)	O
encryption	O
can	O
be	O
configured	O
in	O
two	O
modes	O
:	O
simple	O
and	O
mutual	O
.	O
</s>
<s>
In	O
simple	O
mode	O
,	O
authentication	O
is	O
only	O
performed	O
by	O
the	O
server	B-Application
.	O
</s>
<s>
The	O
mutual	O
version	O
requires	O
the	O
user	O
to	O
install	O
a	O
personal	O
client	O
certificate	O
in	O
the	O
web	B-Application
browser	I-Application
for	O
user	O
authentication	O
.	O
</s>
<s>
In	O
either	O
case	O
,	O
the	O
level	O
of	O
protection	O
depends	O
on	O
the	O
correctness	O
of	O
the	O
implementation	O
of	O
the	O
software	O
and	O
the	O
cryptographic	B-Application
algorithms	I-Application
in	O
use	O
.	O
</s>
<s>
SSL/TLS	B-Protocol
does	O
not	O
prevent	O
the	O
indexing	O
of	O
the	O
site	O
by	O
a	O
web	B-Application
crawler	I-Application
,	O
and	O
in	O
some	O
cases	O
the	O
URI	B-Protocol
of	O
the	O
encrypted	O
resource	O
can	O
be	O
inferred	O
by	O
knowing	O
only	O
the	O
intercepted	O
request/response	O
size	O
.	O
</s>
<s>
Because	O
TLS	B-Protocol
operates	O
at	O
a	O
protocol	O
level	O
below	O
that	O
of	O
HTTP	B-Protocol
and	O
has	O
no	O
knowledge	O
of	O
the	O
higher-level	O
protocols	O
,	O
TLS	B-Protocol
servers	O
can	O
only	O
strictly	O
present	O
one	O
certificate	O
for	O
a	O
particular	O
address	O
and	O
port	B-Protocol
combination	O
.	O
</s>
<s>
In	O
the	O
past	O
,	O
this	O
meant	O
that	O
it	O
was	O
not	O
feasible	O
to	O
use	O
name-based	O
virtual	O
hosting	O
with	O
HTTPS	B-Protocol
.	I-Protocol
</s>
<s>
A	O
solution	O
called	O
Server	B-Protocol
Name	I-Protocol
Indication	I-Protocol
(	O
SNI	O
)	O
exists	O
,	O
which	O
sends	O
the	O
hostname	O
to	O
the	O
server	B-Application
before	O
encrypting	O
the	O
connection	O
,	O
although	O
many	O
old	O
browsers	B-Application
do	O
not	O
support	O
this	O
extension	O
.	O
</s>
<s>
Support	O
for	O
SNI	O
is	O
available	O
since	O
Firefox	B-Application
2	O
,	O
Opera	B-Application
8	O
,	O
Apple	B-Application
Safari	I-Application
2.1	O
,	O
Google	B-Application
Chrome	I-Application
6	O
,	O
and	O
Internet	B-Application
Explorer	I-Application
7	I-Application
on	O
Windows	B-Application
Vista	I-Application
.	O
</s>
<s>
An	O
SSL/TLS	B-Protocol
connection	O
is	O
managed	O
by	O
the	O
first	O
front	O
machine	O
that	O
initiates	O
the	O
TLS	B-Protocol
connection	O
.	O
</s>
<s>
)	O
,	O
this	O
front	O
machine	O
is	O
not	O
the	O
application	O
server	B-Application
and	O
it	O
has	O
to	O
decipher	O
data	O
,	O
solutions	O
have	O
to	O
be	O
found	O
to	O
propagate	O
user	O
authentication	O
information	O
or	O
certificate	O
to	O
the	O
application	O
server	B-Application
,	O
which	O
needs	O
to	O
know	O
who	O
is	O
going	O
to	O
be	O
connected	O
.	O
</s>
<s>
For	O
SSL/TLS	B-Protocol
with	O
mutual	O
authentication	O
,	O
the	O
SSL/TLS	B-Protocol
session	O
is	O
managed	O
by	O
the	O
first	O
server	B-Application
that	O
initiates	O
the	O
connection	O
.	O
</s>
<s>
Security	O
is	O
maximal	O
with	O
mutual	O
SSL/TLS	B-Protocol
,	O
but	O
on	O
the	O
client-side	O
there	O
is	O
no	O
way	O
to	O
properly	O
end	O
the	O
SSL/TLS	B-Protocol
connection	O
and	O
disconnect	O
the	O
user	O
except	O
by	O
waiting	O
for	O
the	O
server	B-Application
session	O
to	O
expire	O
or	O
by	O
closing	O
all	O
related	O
client	O
applications	O
.	O
</s>
<s>
A	O
sophisticated	O
type	O
of	O
man-in-the-middle	O
attack	O
called	O
SSL	B-Protocol
stripping	O
was	O
presented	O
at	O
the	O
2009	O
Blackhat	O
Conference	O
.	O
</s>
<s>
This	O
type	O
of	O
attack	O
defeats	O
the	O
security	O
provided	O
by	O
HTTPS	B-Protocol
by	O
changing	O
the	O
link	O
into	O
an	O
link	O
,	O
taking	O
advantage	O
of	O
the	O
fact	O
that	O
few	O
Internet	O
users	O
actually	O
type	O
"	O
https	B-Protocol
"	O
into	O
their	O
browser	B-Application
interface	O
:	O
they	O
get	O
to	O
a	O
secure	O
site	O
by	O
clicking	O
on	O
a	O
link	O
,	O
and	O
thus	O
are	O
fooled	O
into	O
thinking	O
that	O
they	O
are	O
using	O
HTTPS	B-Protocol
when	O
in	O
fact	O
they	O
are	O
using	O
HTTP	B-Protocol
.	I-Protocol
</s>
<s>
This	O
prompted	O
the	O
development	O
of	O
a	O
countermeasure	O
in	O
HTTP	B-Protocol
called	O
HTTP	B-Protocol
Strict	I-Protocol
Transport	I-Protocol
Security	I-Protocol
.	O
</s>
<s>
HTTPS	B-Protocol
has	O
been	O
shown	O
to	O
be	O
vulnerable	O
to	O
a	O
range	O
of	O
traffic	O
analysis	O
attacks	O
.	O
</s>
<s>
Traffic	O
analysis	O
is	O
possible	O
because	O
SSL/TLS	B-Protocol
encryption	O
changes	O
the	O
contents	O
of	O
traffic	O
,	O
but	O
has	O
minimal	O
impact	O
on	O
the	O
size	O
and	O
timing	O
of	O
traffic	O
.	O
</s>
<s>
The	O
researchers	O
found	O
that	O
,	O
despite	O
HTTPS	B-Protocol
protection	O
in	O
several	O
high-profile	O
,	O
top-of-the-line	O
web	O
applications	O
in	O
healthcare	O
,	O
taxation	O
,	O
investment	O
,	O
and	O
web	O
search	O
,	O
an	O
eavesdropper	O
could	O
infer	O
the	O
illnesses/medications/surgeries	O
of	O
the	O
user	O
,	O
his/her	O
family	O
income	O
,	O
and	O
investment	O
secrets	O
.	O
</s>
<s>
Although	O
this	O
work	O
demonstrated	O
the	O
vulnerability	O
of	O
HTTPS	B-Protocol
to	O
traffic	O
analysis	O
,	O
the	O
approach	O
presented	O
by	O
the	O
authors	O
required	O
manual	O
analysis	O
and	O
focused	O
specifically	O
on	O
web	O
applications	O
protected	O
by	O
HTTPS	B-Protocol
.	I-Protocol
</s>
<s>
The	O
fact	O
that	O
most	O
modern	O
websites	O
,	O
including	O
Google	O
,	O
Yahoo	O
!,	O
and	O
Amazon	O
,	O
use	O
HTTPS	B-Protocol
causes	O
problems	O
for	O
many	O
users	O
trying	O
to	O
access	O
public	B-Application
Wi-Fi	O
hot	O
spots	O
,	O
because	O
a	O
Wi-Fi	O
hot	O
spot	O
login	O
page	O
fails	O
to	O
load	O
if	O
the	O
user	O
tries	O
to	O
open	O
an	O
HTTPS	B-Protocol
resource	O
.	O
</s>
<s>
Several	O
websites	O
,	O
such	O
as	O
,	O
guarantee	O
that	O
they	O
will	O
always	O
remain	O
accessible	O
by	O
HTTP	B-Protocol
.	I-Protocol
</s>
<s>
Netscape	O
Communications	O
created	O
HTTPS	B-Protocol
in	O
1994	O
for	O
its	O
Netscape	B-Protocol
Navigator	I-Protocol
web	B-Application
browser	I-Application
.	O
</s>
<s>
Originally	O
,	O
HTTPS	B-Protocol
was	O
used	O
with	O
the	O
SSL	B-Protocol
protocol	O
.	O
</s>
<s>
As	O
SSL	B-Protocol
evolved	O
into	O
Transport	B-Protocol
Layer	I-Protocol
Security	I-Protocol
(	O
TLS	B-Protocol
)	O
,	O
HTTPS	B-Protocol
was	O
formally	O
specified	O
by	O
RFC	O
2818	O
in	O
May	O
2000	O
.	O
</s>
<s>
Google	O
announced	O
in	O
February	O
2018	O
that	O
its	O
Chrome	B-Application
browser	I-Application
would	O
mark	O
HTTP	B-Protocol
sites	O
as	O
"	O
Not	O
Secure	O
"	O
after	O
July	O
2018	O
.	O
</s>
<s>
This	O
move	O
was	O
to	O
encourage	O
website	O
owners	O
to	O
implement	O
HTTPS	B-Protocol
,	O
as	O
an	O
effort	O
to	O
make	O
the	O
World	O
Wide	O
Web	O
more	O
secure	O
.	O
</s>
