<s>
Temporal	B-Protocol
Key	I-Protocol
Integrity	I-Protocol
Protocol	I-Protocol
(	O
TKIP	O
)	O
is	O
a	O
security	B-Protocol
protocol	I-Protocol
used	O
in	O
the	O
IEEE	O
802.11	O
wireless	O
networking	O
standard	O
.	O
</s>
<s>
TKIP	O
was	O
designed	O
by	O
the	O
IEEE	B-Protocol
802.11i	I-Protocol
task	O
group	O
and	O
the	O
Wi-Fi	O
Alliance	O
as	O
an	O
interim	O
solution	O
to	O
replace	O
WEP	B-Protocol
without	O
requiring	O
the	O
replacement	O
of	O
legacy	O
hardware	O
.	O
</s>
<s>
This	O
was	O
necessary	O
because	O
the	O
breaking	O
of	O
WEP	B-Protocol
had	O
left	O
Wi-Fi	O
networks	O
without	O
viable	O
link-layer	O
security	O
,	O
and	O
a	O
solution	O
was	O
required	O
for	O
already	O
deployed	O
hardware	O
.	O
</s>
<s>
The	O
IEEE	O
endorsed	O
the	O
final	O
version	O
of	O
TKIP	O
,	O
along	O
with	O
more	O
robust	O
solutions	O
such	O
as	O
802.1X	O
and	O
the	O
AES	B-Algorithm
based	O
CCMP	B-Protocol
,	O
when	O
they	O
published	O
IEEE	B-Protocol
802.11i-2004	I-Protocol
on	O
23	O
July	O
2004	O
.	O
</s>
<s>
TKIP	O
and	O
the	O
related	O
WPA	O
standard	O
implement	O
three	O
new	O
security	O
features	O
to	O
address	O
security	O
problems	O
encountered	O
in	O
WEP	B-Protocol
protected	O
networks	O
.	O
</s>
<s>
First	O
,	O
TKIP	O
implements	O
a	O
key	O
mixing	O
function	O
that	O
combines	O
the	O
secret	O
root	O
key	O
with	O
the	O
initialization	B-Algorithm
vector	I-Algorithm
before	O
passing	O
it	O
to	O
the	O
RC4	B-Algorithm
cipher	I-Algorithm
initialization	O
.	O
</s>
<s>
WEP	B-Protocol
,	O
in	O
comparison	O
,	O
merely	O
concatenated	O
the	O
initialization	B-Algorithm
vector	I-Algorithm
to	O
the	O
root	O
key	O
,	O
and	O
passed	O
this	O
value	O
to	O
the	O
RC4	B-Algorithm
routine	O
.	O
</s>
<s>
This	O
permitted	O
the	O
vast	O
majority	O
of	O
the	O
RC4	B-Algorithm
based	O
WEP	B-Protocol
related	O
key	O
attacks	O
.	O
</s>
<s>
Packets	B-Protocol
received	O
out	O
of	O
order	O
will	O
be	O
rejected	O
by	O
the	O
access	O
point	O
.	O
</s>
<s>
To	O
be	O
able	O
to	O
run	O
on	O
legacy	O
WEP	B-Protocol
hardware	O
with	O
minor	O
upgrades	O
,	O
TKIP	O
uses	O
RC4	B-Algorithm
as	O
its	O
cipher	O
.	O
</s>
<s>
TKIP	O
also	O
provides	O
a	O
rekeying	B-General_Concept
mechanism	O
.	O
</s>
<s>
TKIP	O
ensures	O
that	O
every	O
data	B-Protocol
packet	I-Protocol
is	O
sent	O
with	O
a	O
unique	O
encryption	O
key( Interim	O
Key/Temporal	O
Key	O
+	O
Packet	B-Protocol
Sequence	O
Counter	O
)	O
.	O
</s>
<s>
The	O
message	O
integrity	O
check	O
prevents	O
forged	O
packets	B-Protocol
from	O
being	O
accepted	O
.	O
</s>
<s>
Under	O
WEP	B-Protocol
it	O
was	O
possible	O
to	O
alter	O
a	O
packet	B-Protocol
whose	O
content	O
was	O
known	O
even	O
if	O
it	O
had	O
not	O
been	O
decrypted	O
.	O
</s>
<s>
TKIP	O
uses	O
the	O
same	O
underlying	O
mechanism	O
as	O
WEP	B-Protocol
,	O
and	O
consequently	O
is	O
vulnerable	O
to	O
a	O
number	O
of	O
similar	O
attacks	O
.	O
</s>
<s>
The	O
message	O
integrity	O
check	O
,	O
per-packet	O
key	O
hashing	B-Error_Name
,	O
broadcast	O
key	O
rotation	O
,	O
and	O
a	O
sequence	O
counter	O
discourage	O
many	O
attacks	O
.	O
</s>
<s>
The	O
key	O
mixing	O
function	O
also	O
eliminates	O
the	O
WEP	B-Protocol
key	I-Protocol
recovery	O
attacks	O
.	O
</s>
<s>
TKIP	O
is	O
vulnerable	O
to	O
a	O
MIC	O
key	O
recovery	O
attack	O
that	O
,	O
if	O
successfully	O
executed	O
,	O
permits	O
an	O
attacker	O
to	O
transmit	O
and	O
decrypt	O
arbitrary	O
packets	B-Protocol
on	O
the	O
network	O
being	O
attacked	O
.	O
</s>
<s>
On	O
November	O
8	O
,	O
2008	O
,	O
Martin	O
Beck	O
and	O
Erik	O
Tews	O
released	O
a	O
paper	O
detailing	O
how	O
to	O
recover	O
the	O
MIC	O
key	O
and	O
transmit	O
a	O
few	O
packets	B-Protocol
.	O
</s>
<s>
This	O
attack	O
was	O
improved	O
by	O
Mathy	O
Vanhoef	O
and	O
Frank	O
Piessens	O
in	O
2013	O
,	O
where	O
they	O
increase	O
the	O
amount	O
of	O
packets	B-Protocol
an	O
attacker	O
can	O
transmit	O
,	O
and	O
show	O
how	O
an	O
attacker	O
can	O
also	O
decrypt	O
arbitrary	O
packets	B-Protocol
.	O
</s>
<s>
The	O
basis	O
of	O
the	O
attack	O
is	O
an	O
extension	O
of	O
the	O
WEP	B-Protocol
chop-chop	O
attack	O
.	O
</s>
<s>
Because	O
WEP	B-Protocol
uses	O
a	O
cryptographically	O
insecure	O
checksum	O
mechanism	O
(	O
CRC32	O
)	O
,	O
an	O
attacker	O
can	O
guess	O
individual	O
bytes	O
of	O
a	O
packet	B-Protocol
,	O
and	O
the	O
wireless	O
access	O
point	O
will	O
confirm	O
or	O
deny	O
whether	O
or	O
not	O
the	O
guess	O
is	O
correct	O
.	O
</s>
<s>
If	O
the	O
guess	O
is	O
correct	O
,	O
the	O
attacker	O
will	O
be	O
able	O
to	O
detect	O
the	O
guess	O
is	O
correct	O
and	O
continue	O
to	O
guess	O
other	O
bytes	O
of	O
the	O
packet	B-Protocol
.	O
</s>
<s>
However	O
,	O
unlike	O
the	O
chop-chop	O
attack	O
against	O
a	O
WEP	B-Protocol
network	O
,	O
the	O
attacker	O
must	O
wait	O
for	O
at	O
least	O
60	O
seconds	O
after	O
an	O
incorrect	O
guess	O
(	O
a	O
successful	O
circumvention	O
of	O
the	O
CRC32	O
mechanism	O
)	O
before	O
continuing	O
the	O
attack	O
.	O
</s>
<s>
Because	O
ARP	O
packets	B-Protocol
are	O
easily	O
identified	O
by	O
their	O
size	O
,	O
and	O
the	O
vast	O
majority	O
of	O
the	O
contents	O
of	O
this	O
packet	B-Protocol
would	O
be	O
known	O
to	O
an	O
attacker	O
,	O
the	O
number	O
of	O
bytes	O
an	O
attacker	O
must	O
guess	O
using	O
the	O
above	O
method	O
is	O
rather	O
small	O
(	O
approximately	O
14	O
bytes	O
)	O
.	O
</s>
<s>
Beck	O
and	O
Tews	O
estimate	O
recovery	O
of	O
12	O
bytes	O
is	O
possible	O
in	O
about	O
12	O
minutes	O
on	O
a	O
typical	O
network	O
,	O
which	O
would	O
allow	O
an	O
attacker	O
to	O
transmit	O
3	O
–	O
7	O
packets	B-Protocol
of	O
at	O
most	O
28	O
bytes	O
.	O
</s>
<s>
Vanhoef	O
and	O
Piessens	O
improved	O
this	O
technique	O
by	O
relying	O
on	O
fragmentation	O
,	O
allowing	O
an	O
attacker	O
to	O
transmit	O
arbitrary	O
many	O
packets	B-Protocol
,	O
each	O
at	O
most	O
112	O
bytes	O
in	O
size	O
.	O
</s>
<s>
The	O
Vanhoef	O
–	O
Piessens	O
attacks	O
also	O
can	O
be	O
used	O
to	O
decrypt	O
arbitrary	O
packets	B-Protocol
of	O
the	O
attack	O
's	O
choice	O
.	O
</s>
<s>
An	O
attacker	O
already	O
has	O
access	O
to	O
the	O
entire	O
ciphertext	O
packet	B-Protocol
.	O
</s>
<s>
Upon	O
retrieving	O
the	O
entire	O
plaintext	O
of	O
the	O
same	O
packet	B-Protocol
,	O
the	O
attacker	O
has	O
access	O
to	O
the	O
keystream	O
of	O
the	O
packet	B-Protocol
,	O
as	O
well	O
as	O
the	O
MIC	O
code	O
of	O
the	O
session	O
.	O
</s>
<s>
Using	O
this	O
information	O
the	O
attacker	O
can	O
construct	O
a	O
new	O
packet	B-Protocol
and	O
transmit	O
it	O
on	O
the	O
network	O
.	O
</s>
<s>
To	O
circumvent	O
the	O
WPA	O
implemented	O
replay	O
protection	O
,	O
the	O
attacks	O
use	O
QoS	O
channels	O
to	O
transmit	O
these	O
newly	O
constructed	O
packets	B-Protocol
.	O
</s>
<s>
An	O
attacker	O
able	O
to	O
transmit	O
these	O
packets	B-Protocol
may	O
be	O
able	O
to	O
implement	O
any	O
number	O
of	O
attacks	O
,	O
including	O
ARP	O
poisoning	O
attacks	O
,	O
denial	O
of	O
service	O
,	O
and	O
other	O
similar	O
attacks	O
,	O
with	O
no	O
need	O
of	O
being	O
associated	O
with	O
the	O
network	O
.	O
</s>
<s>
A	O
group	O
of	O
security	O
researchers	O
at	O
the	O
Information	O
Security	O
Group	O
at	O
Royal	O
Holloway	O
,	O
University	O
of	O
London	O
reported	O
a	O
theoretical	O
attack	O
on	O
TKIP	O
which	O
exploits	O
the	O
underlying	O
RC4	B-Algorithm
encryption	O
mechanism	O
.	O
</s>
<s>
TKIP	O
uses	O
a	O
similar	O
key	O
structure	O
to	O
WEP	B-Protocol
with	O
the	O
low	O
16-bit	O
value	O
of	O
a	O
sequence	O
counter	O
(	O
used	O
to	O
prevent	O
replay	O
attacks	O
)	O
being	O
expanded	O
into	O
the	O
24-bit	O
"	O
IV	O
"	O
,	O
and	O
this	O
sequence	O
counter	O
always	O
increment	O
on	O
every	O
new	O
packet	B-Protocol
.	O
</s>
<s>
An	O
attacker	O
can	O
use	O
this	O
key	O
structure	O
to	O
improve	O
existing	O
attacks	O
on	O
RC4	B-Algorithm
.	O
</s>
<s>
In	O
2015	O
,	O
security	O
researchers	O
from	O
KU	O
Leuven	O
presented	O
new	O
attacks	O
against	O
RC4	B-Algorithm
in	O
both	O
TLS	O
and	O
WPA-TKIP	O
.	O
</s>
<s>
The	O
attack	O
against	O
WPA-TKIP	O
can	O
be	O
completed	O
within	O
an	O
hour	O
,	O
and	O
allows	O
an	O
attacker	O
to	O
decrypt	O
and	O
inject	O
arbitrary	O
packets	B-Protocol
.	O
</s>
<s>
ZDNet	O
reported	O
on	O
June	O
18	O
,	O
2010	O
,	O
that	O
WEP	B-Protocol
&	O
TKIP	O
would	O
soon	O
be	O
disallowed	O
on	O
Wi-Fi	O
devices	O
by	O
the	O
Wi-Fi	O
alliance	O
.	O
</s>
