<s>
The	O
Advanced	B-Algorithm
Encryption	I-Algorithm
Standard	I-Algorithm
(	O
AES	B-Algorithm
)	O
,	O
also	O
known	O
by	O
its	O
original	O
name	O
Rijndael	B-Algorithm
(	O
)	O
,	O
is	O
a	O
specification	O
for	O
the	O
encryption	O
of	O
electronic	O
data	O
established	O
by	O
the	O
U.S.	O
National	O
Institute	O
of	O
Standards	O
and	O
Technology	O
(	O
NIST	O
)	O
in	O
2001	O
.	O
</s>
<s>
AES	B-Algorithm
is	O
a	O
variant	O
of	O
the	O
Rijndael	B-Algorithm
block	O
cipher	B-Application
developed	O
by	O
two	O
Belgian	O
cryptographers	O
,	O
Joan	O
Daemen	O
and	O
Vincent	O
Rijmen	O
,	O
who	O
submitted	O
a	O
proposal	O
to	O
NIST	O
during	O
the	O
AES	B-Algorithm
selection	O
process	O
.	O
</s>
<s>
Rijndael	B-Algorithm
is	O
a	O
family	O
of	O
ciphers	B-Application
with	O
different	O
key	O
and	O
block	O
sizes	O
.	O
</s>
<s>
For	O
AES	B-Algorithm
,	O
NIST	O
selected	O
three	O
members	O
of	O
the	O
Rijndael	B-Algorithm
family	O
,	O
each	O
with	O
a	O
block	O
size	O
of	O
128	O
bits	O
,	O
but	O
three	O
different	O
key	O
lengths	O
:	O
128	O
,	O
192	O
and	O
256	O
bits	O
.	O
</s>
<s>
AES	B-Algorithm
has	O
been	O
adopted	O
by	O
the	O
U.S.	O
government	O
.	O
</s>
<s>
It	O
supersedes	O
the	O
Data	B-Algorithm
Encryption	I-Algorithm
Standard	I-Algorithm
(	O
DES	B-Algorithm
)	O
,	O
which	O
was	O
published	O
in	O
1977	O
.	O
</s>
<s>
The	O
algorithm	O
described	O
by	O
AES	B-Algorithm
is	O
a	O
symmetric-key	B-Algorithm
algorithm	I-Algorithm
,	O
meaning	O
the	O
same	O
key	O
is	O
used	O
for	O
both	O
encrypting	O
and	O
decrypting	O
the	O
data	O
.	O
</s>
<s>
In	O
the	O
United	O
States	O
,	O
AES	B-Algorithm
was	O
announced	O
by	O
the	O
NIST	O
as	O
U.S.	O
FIPS	O
PUB	O
197	O
(	O
FIPS	B-Algorithm
197	I-Algorithm
)	O
on	O
November	O
26	O
,	O
2001	O
.	O
</s>
<s>
This	O
announcement	O
followed	O
a	O
five-year	O
standardization	O
process	O
in	O
which	O
fifteen	O
competing	O
designs	O
were	O
presented	O
and	O
evaluated	O
,	O
before	O
the	O
Rijndael	B-Algorithm
cipher	I-Algorithm
was	O
selected	O
as	O
the	O
most	O
suitable	O
.	O
</s>
<s>
AES	B-Algorithm
is	O
included	O
in	O
the	O
ISO/IEC	O
18033-3	O
standard	O
.	O
</s>
<s>
AES	B-Algorithm
became	O
effective	O
as	O
a	O
U.S.	O
federal	O
government	O
standard	O
on	O
May	O
26	O
,	O
2002	O
,	O
after	O
approval	O
by	O
the	O
U.S.	O
Secretary	O
of	O
Commerce	O
.	O
</s>
<s>
AES	B-Algorithm
is	O
available	O
in	O
many	O
different	O
encryption	O
packages	O
,	O
and	O
is	O
the	O
first	O
(	O
and	O
only	O
)	O
publicly	O
accessible	O
cipher	B-Application
approved	O
by	O
the	O
U.S.	O
National	O
Security	O
Agency	O
(	O
NSA	O
)	O
for	O
top	O
secret	O
information	O
when	O
used	O
in	O
an	O
NSA	O
approved	O
cryptographic	O
module	O
.	O
</s>
<s>
The	O
Advanced	B-Algorithm
Encryption	I-Algorithm
Standard	I-Algorithm
(	O
AES	B-Algorithm
)	O
is	O
defined	O
in	O
each	O
of	O
:	O
</s>
<s>
AES	B-Algorithm
is	O
based	O
on	O
a	O
design	O
principle	O
known	O
as	O
a	O
substitution	B-Algorithm
–	I-Algorithm
permutation	I-Algorithm
network	I-Algorithm
,	O
and	O
is	O
efficient	O
in	O
both	O
software	O
and	O
hardware	O
.	O
</s>
<s>
Unlike	O
its	O
predecessor	O
DES	B-Algorithm
,	O
AES	B-Algorithm
does	O
not	O
use	O
a	O
Feistel	B-Algorithm
network	I-Algorithm
.	O
</s>
<s>
AES	B-Algorithm
is	O
a	O
variant	O
of	O
Rijndael	B-Algorithm
,	O
with	O
a	O
fixed	O
block	O
size	O
of	O
128	O
bits	O
,	O
and	O
a	O
key	O
size	O
of	O
128	O
,	O
192	O
,	O
or	O
256	O
bits	O
.	O
</s>
<s>
By	O
contrast	O
,	O
Rijndael	B-Algorithm
per	O
se	O
is	O
specified	O
with	O
block	O
and	O
key	O
sizes	O
that	O
may	O
be	O
any	O
multiple	O
of	O
32	O
bits	O
,	O
with	O
a	O
minimum	O
of	O
128	O
and	O
a	O
maximum	O
of	O
256	O
bits	O
.	O
</s>
<s>
Most	O
AES	B-Algorithm
calculations	O
are	O
done	O
in	O
a	O
particular	O
finite	O
field	O
.	O
</s>
<s>
AES	B-Algorithm
operates	O
on	O
a	O
4	O
×	O
4	O
column-major	B-Data_Structure
order	I-Data_Structure
array	O
of	O
16	O
bytes	O
termed	O
the	O
state	O
:	O
</s>
<s>
The	O
key	O
size	O
used	O
for	O
an	O
AES	B-Algorithm
cipher	I-Algorithm
specifies	O
the	O
number	O
of	O
transformation	O
rounds	O
that	O
convert	O
the	O
input	O
,	O
called	O
the	O
plaintext	O
,	O
into	O
the	O
final	O
output	O
,	O
called	O
the	O
ciphertext	O
.	O
</s>
<s>
round	O
keys	O
are	O
derived	O
from	O
the	O
cipher	B-Application
key	O
using	O
the	O
AES	B-Algorithm
key	I-Algorithm
schedule	I-Algorithm
.	O
</s>
<s>
AES	B-Algorithm
requires	O
a	O
separate	O
128-bit	O
round	O
key	O
block	O
for	O
each	O
round	O
plus	O
one	O
more	O
.	O
</s>
<s>
a	O
non-linear	B-Architecture
substitution	O
step	O
where	O
each	O
byte	O
is	O
replaced	O
with	O
another	O
according	O
to	O
a	O
lookup	O
table	O
.	O
</s>
<s>
In	O
the	O
step	O
,	O
each	O
byte	O
in	O
the	O
state	O
array	O
is	O
replaced	O
with	O
a	O
using	O
an	O
8-bit	O
substitution	B-Algorithm
box	I-Algorithm
.	O
</s>
<s>
This	O
operation	O
provides	O
the	O
non-linearity	O
in	O
the	O
cipher	B-Application
.	O
</s>
<s>
The	O
S-box	B-Algorithm
used	O
is	O
derived	O
from	O
the	O
multiplicative	O
inverse	O
over	O
,	O
known	O
to	O
have	O
good	O
non-linearity	O
properties	O
.	O
</s>
<s>
To	O
avoid	O
attacks	O
based	O
on	O
simple	O
algebraic	O
properties	O
,	O
the	O
S-box	B-Algorithm
is	O
constructed	O
by	O
combining	O
the	O
inverse	O
function	O
with	O
an	O
invertible	O
affine	B-Algorithm
transformation	I-Algorithm
.	O
</s>
<s>
The	O
S-box	B-Algorithm
is	O
also	O
chosen	O
to	O
avoid	O
any	O
fixed	O
points	O
(	O
and	O
so	O
is	O
a	O
derangement	O
)	O
,	O
i.e.	O
,	O
,	O
and	O
also	O
any	O
opposite	O
fixed	O
points	O
,	O
i.e.	O
,	O
.	O
</s>
<s>
While	O
performing	O
the	O
decryption	O
,	O
the	O
step	O
(	O
the	O
inverse	O
of	O
)	O
is	O
used	O
,	O
which	O
requires	O
first	O
taking	O
the	O
inverse	O
of	O
the	O
affine	B-Algorithm
transformation	I-Algorithm
and	O
then	O
finding	O
the	O
multiplicative	O
inverse	O
.	O
</s>
<s>
The	O
step	O
operates	O
on	O
the	O
rows	O
of	O
the	O
state	O
;	O
it	O
cyclically	O
shifts	O
the	O
bytes	O
in	O
each	O
row	O
by	O
a	O
certain	O
offset	B-General_Concept
.	O
</s>
<s>
For	O
AES	B-Algorithm
,	O
the	O
first	O
row	O
is	O
left	O
unchanged	O
.	O
</s>
<s>
Similarly	O
,	O
the	O
third	O
and	O
fourth	O
rows	O
are	O
shifted	O
by	O
offsets	B-General_Concept
of	O
two	O
and	O
three	O
respectively	O
.	O
</s>
<s>
The	O
importance	O
of	O
this	O
step	O
is	O
to	O
avoid	O
the	O
columns	O
being	O
encrypted	O
independently	O
,	O
in	O
which	O
case	O
AES	B-Algorithm
would	O
degenerate	O
into	O
four	O
independent	O
block	O
ciphers	B-Application
.	O
</s>
<s>
In	O
the	O
step	O
,	O
the	O
four	O
bytes	O
of	O
each	O
column	O
of	O
the	O
state	O
are	O
combined	O
using	O
an	O
invertible	O
linear	B-Architecture
transformation	I-Architecture
.	O
</s>
<s>
Together	O
with	O
,	O
provides	O
diffusion	O
in	O
the	O
cipher	B-Application
.	O
</s>
<s>
The	O
step	O
can	O
also	O
be	O
viewed	O
as	O
a	O
multiplication	O
by	O
the	O
shown	O
particular	O
MDS	B-General_Concept
matrix	I-General_Concept
in	O
the	O
finite	O
field	O
.	O
</s>
<s>
This	O
process	O
is	O
described	O
further	O
in	O
the	O
article	O
Rijndael	B-Algorithm
MixColumns	I-Algorithm
.	O
</s>
<s>
For	O
each	O
round	O
,	O
a	O
subkey	O
is	O
derived	O
from	O
the	O
main	O
key	O
using	O
Rijndael	B-Algorithm
's	I-Algorithm
key	I-Algorithm
schedule	I-Algorithm
;	O
each	O
subkey	O
is	O
the	O
same	O
size	O
as	O
the	O
state	O
.	O
</s>
<s>
On	O
systems	O
with	O
32-bit	O
or	O
larger	O
words	O
,	O
it	O
is	O
possible	O
to	O
speed	O
up	O
execution	O
of	O
this	O
cipher	B-Application
by	O
combining	O
the	O
and	O
steps	O
with	O
the	O
step	O
by	O
transforming	O
them	O
into	O
a	O
sequence	O
of	O
table	O
lookups	O
.	O
</s>
<s>
The	O
National	O
Security	O
Agency	O
(	O
NSA	O
)	O
reviewed	O
all	O
the	O
AES	B-Algorithm
finalists	O
,	O
including	O
Rijndael	B-Algorithm
,	O
and	O
stated	O
that	O
all	O
of	O
them	O
were	O
secure	O
enough	O
for	O
U.S.	O
Government	O
non-classified	O
data	O
.	O
</s>
<s>
In	O
June	O
2003	O
,	O
the	O
U.S.	O
Government	O
announced	O
that	O
AES	B-Algorithm
could	O
be	O
used	O
to	O
protect	O
classified	O
information	O
:	O
</s>
<s>
The	O
design	O
and	O
strength	O
of	O
all	O
key	O
lengths	O
of	O
the	O
AES	B-Algorithm
algorithm	O
(	O
i.e.	O
,	O
128	O
,	O
192	O
and	O
256	O
)	O
are	O
sufficient	O
to	O
protect	O
classified	O
information	O
up	O
to	O
the	O
SECRET	O
level	O
.	O
</s>
<s>
The	O
implementation	O
of	O
AES	B-Algorithm
in	O
products	O
intended	O
to	O
protect	O
national	O
security	O
systems	O
and/or	O
information	O
must	O
be	O
reviewed	O
and	O
certified	O
by	O
NSA	O
prior	O
to	O
their	O
acquisition	O
and	O
use	O
.	O
</s>
<s>
AES	B-Algorithm
has	O
10	O
rounds	O
for	O
128-bit	O
keys	O
,	O
12	O
rounds	O
for	O
192-bit	O
keys	O
,	O
and	O
14	O
rounds	O
for	O
256-bit	O
keys	O
.	O
</s>
<s>
The	O
largest	O
successful	O
publicly	O
known	O
brute-force	O
attack	O
against	O
a	O
widely	O
implemented	O
block-cipher	O
encryption	O
algorithm	O
was	O
against	O
a	O
64-bit	O
RC5	B-Algorithm
key	O
by	O
distributed.net	O
in	O
2006	O
.	O
</s>
<s>
Key	O
length	O
in	O
itself	O
does	O
not	O
imply	O
security	O
against	O
attacks	O
,	O
since	O
there	O
are	O
ciphers	B-Application
with	O
very	O
long	O
keys	O
that	O
have	O
been	O
found	O
to	O
be	O
vulnerable	O
.	O
</s>
<s>
AES	B-Algorithm
has	O
a	O
fairly	O
simple	O
algebraic	O
framework	O
.	O
</s>
<s>
In	O
2002	O
,	O
a	O
theoretical	O
attack	O
,	O
named	O
the	O
"	O
XSL	O
attack	O
"	O
,	O
was	O
announced	O
by	O
Nicolas	O
Courtois	O
and	O
Josef	O
Pieprzyk	O
,	O
purporting	O
to	O
show	O
a	O
weakness	O
in	O
the	O
AES	B-Algorithm
algorithm	O
,	O
partially	O
due	O
to	O
the	O
low	O
complexity	O
of	O
its	O
nonlinear	O
components	O
.	O
</s>
<s>
Since	O
then	O
,	O
other	O
papers	O
have	O
shown	O
that	O
the	O
attack	O
,	O
as	O
originally	O
presented	O
,	O
is	O
unworkable	O
;	O
see	O
XSL	O
attack	O
on	O
block	O
ciphers	B-Application
.	O
</s>
<s>
During	O
the	O
AES	B-Algorithm
selection	O
process	O
,	O
developers	O
of	O
competing	O
algorithms	O
wrote	O
of	O
Rijndael	B-Algorithm
's	O
algorithm	O
"	O
we	O
are	O
concerned	O
about	O
 [ its ] 	O
use	O
...	O
in	O
security-critical	O
applications.	O
"	O
</s>
<s>
In	O
October	O
2000	O
,	O
however	O
,	O
at	O
the	O
end	O
of	O
the	O
AES	B-Algorithm
selection	O
process	O
,	O
Bruce	O
Schneier	O
,	O
a	O
developer	O
of	O
the	O
competing	O
algorithm	O
Twofish	B-Algorithm
,	O
wrote	O
that	O
while	O
he	O
thought	O
successful	O
academic	O
attacks	O
on	O
Rijndael	B-Algorithm
would	O
be	O
developed	O
someday	O
,	O
he	O
"	O
did	O
not	O
believe	O
that	O
anyone	O
will	O
ever	O
discover	O
an	O
attack	O
that	O
will	O
allow	O
someone	O
to	O
read	O
Rijndael	B-Algorithm
traffic.	O
"	O
</s>
<s>
Until	O
May	O
2009	O
,	O
the	O
only	O
successful	O
published	O
attacks	O
against	O
the	O
full	O
AES	B-Algorithm
were	O
side-channel	O
attacks	O
on	O
some	O
specific	O
implementations	O
.	O
</s>
<s>
In	O
2009	O
,	O
a	O
new	O
related-key	O
attack	O
was	O
discovered	O
that	O
exploits	O
the	O
simplicity	O
of	O
AES	B-Algorithm
's	O
key	O
schedule	O
and	O
has	O
a	O
complexity	O
of	O
2119	O
.	O
</s>
<s>
This	O
new	O
attack	O
,	O
by	O
Alex	O
Biryukov	O
,	O
Orr	O
Dunkelman	O
,	O
Nathan	O
Keller	O
,	O
Dmitry	O
Khovratovich	O
,	O
and	O
Adi	O
Shamir	O
,	O
is	O
against	O
AES-256	B-Algorithm
that	O
uses	O
only	O
two	O
related	O
keys	O
and	O
239	O
time	O
to	O
recover	O
the	O
complete	O
256-bit	O
key	O
of	O
a	O
9-round	O
version	O
,	O
or	O
245	O
time	O
for	O
a	O
10-round	O
version	O
with	O
a	O
stronger	O
type	O
of	O
related	O
subkey	O
attack	O
,	O
or	O
270	O
time	O
for	O
an	O
11-round	O
version	O
.	O
</s>
<s>
256-bit	O
AES	B-Algorithm
uses	O
14	O
rounds	O
,	O
so	O
these	O
attacks	O
are	O
not	O
effective	O
against	O
full	O
AES	B-Algorithm
.	O
</s>
<s>
The	O
practicality	O
of	O
these	O
attacks	O
with	O
stronger	O
related	O
keys	O
has	O
been	O
criticized	O
,	O
for	O
instance	O
,	O
by	O
the	O
paper	O
on	O
chosen-key-relations-in-the-middle	O
attacks	O
on	O
AES-128	B-Algorithm
authored	O
by	O
Vincent	O
Rijmen	O
in	O
2010	O
.	O
</s>
<s>
In	O
November	O
2009	O
,	O
the	O
first	O
known-key	B-General_Concept
distinguishing	I-General_Concept
attack	I-General_Concept
against	O
a	O
reduced	O
8-round	O
version	O
of	O
AES-128	B-Algorithm
was	O
released	O
as	O
a	O
preprint	O
.	O
</s>
<s>
This	O
known-key	B-General_Concept
distinguishing	I-General_Concept
attack	I-General_Concept
is	O
an	O
improvement	O
of	O
the	O
rebound	O
,	O
or	O
the	O
start-from-the-middle	O
attack	O
,	O
against	O
AES-like	O
permutations	B-Algorithm
,	O
which	O
view	O
two	O
consecutive	O
rounds	O
of	O
permutation	B-Algorithm
as	O
the	O
application	O
of	O
a	O
so-called	O
Super-S-box	O
.	O
</s>
<s>
It	O
works	O
on	O
the	O
8-round	O
version	O
of	O
AES-128	B-Algorithm
,	O
with	O
a	O
time	O
complexity	O
of	O
248	O
,	O
and	O
a	O
memory	O
complexity	O
of	O
232	O
.	O
</s>
<s>
128-bit	O
AES	B-Algorithm
uses	O
10	O
rounds	O
,	O
so	O
this	O
attack	O
is	O
not	O
effective	O
against	O
full	O
AES-128	B-Algorithm
.	O
</s>
<s>
The	O
first	O
key-recovery	O
attacks	O
on	O
full	O
AES	B-Algorithm
were	O
by	O
Andrey	O
Bogdanov	O
,	O
Dmitry	O
Khovratovich	O
,	O
and	O
Christian	O
Rechberger	O
,	O
and	O
were	O
published	O
in	O
2011	O
.	O
</s>
<s>
It	O
requires	O
2126.2	O
operations	O
to	O
recover	O
an	O
AES-128	B-Algorithm
key	O
.	O
</s>
<s>
For	O
AES-192	B-Algorithm
and	O
AES-256	B-Algorithm
,	O
2190.2	O
and	O
2254.6	O
operations	O
are	O
needed	O
,	O
respectively	O
.	O
</s>
<s>
This	O
result	O
has	O
been	O
further	O
improved	O
to	O
2126.0	O
for	O
AES-128	B-Algorithm
,	O
2189.9	O
for	O
AES-192	B-Algorithm
and	O
2254.3	O
for	O
AES-256	B-Algorithm
,	O
which	O
are	O
the	O
current	O
best	O
results	O
in	O
key	O
recovery	O
attack	O
against	O
AES	B-Algorithm
.	O
</s>
<s>
Also	O
,	O
the	O
authors	O
calculate	O
the	O
best	O
attack	O
using	O
their	O
technique	O
on	O
AES	B-Algorithm
with	O
a	O
128-bit	O
key	O
requires	O
storing	O
288	O
bits	O
of	O
data	O
.	O
</s>
<s>
As	O
such	O
,	O
there	O
are	O
no	O
practical	O
implications	O
on	O
AES	B-Algorithm
security	O
.	O
</s>
<s>
According	O
to	O
the	O
Snowden	O
documents	O
,	O
the	O
NSA	O
is	O
doing	O
research	O
on	O
whether	O
a	O
cryptographic	O
attack	O
based	O
on	O
tau	B-General_Concept
statistic	I-General_Concept
may	O
help	O
to	O
break	O
AES	B-Algorithm
.	O
</s>
<s>
At	O
present	O
,	O
there	O
is	O
no	O
known	O
practical	O
attack	O
that	O
would	O
allow	O
someone	O
without	O
knowledge	O
of	O
the	O
key	O
to	O
read	O
data	O
encrypted	O
by	O
AES	B-Algorithm
when	O
correctly	O
implemented	O
.	O
</s>
<s>
Side-channel	O
attacks	O
do	O
not	O
attack	O
the	O
cipher	B-Application
as	O
a	O
black	B-Device
box	I-Device
,	O
and	O
thus	O
are	O
not	O
related	O
to	O
cipher	B-Application
security	O
as	O
defined	O
in	O
the	O
classical	O
context	O
,	O
but	O
are	O
important	O
in	O
practice	O
.	O
</s>
<s>
They	O
attack	O
implementations	O
of	O
the	O
cipher	B-Application
on	O
hardware	O
or	O
software	O
systems	O
that	O
inadvertently	O
leak	O
data	O
.	O
</s>
<s>
There	O
are	O
several	O
such	O
known	O
attacks	O
on	O
various	O
implementations	O
of	O
AES	B-Algorithm
.	O
</s>
<s>
In	O
April	O
2005	O
,	O
D	O
.	O
J	O
.	O
Bernstein	O
announced	O
a	O
cache-timing	O
attack	O
that	O
he	O
used	O
to	O
break	O
a	O
custom	O
server	O
that	O
used	O
OpenSSL	B-Language
's	O
AES	B-Algorithm
encryption	I-Algorithm
.	O
</s>
<s>
In	O
October	O
2005	O
,	O
Dag	O
Arne	O
Osvik	O
,	O
Adi	O
Shamir	O
and	O
Eran	O
Tromer	O
presented	O
a	O
paper	O
demonstrating	O
several	O
cache-timing	O
attacks	O
against	O
the	O
implementations	O
in	O
AES	B-Algorithm
found	O
in	O
OpenSSL	B-Language
and	O
Linux	O
's	O
dm-crypt	O
partition	O
encryption	O
function	O
.	O
</s>
<s>
One	O
attack	O
was	O
able	O
to	O
obtain	O
an	O
entire	O
AES	B-Algorithm
key	I-Algorithm
after	O
only	O
800operations	O
triggering	O
encryptions	O
,	O
in	O
a	O
total	O
of	O
65milliseconds	O
.	O
</s>
<s>
This	O
attack	O
requires	O
the	O
attacker	O
to	O
be	O
able	O
to	O
run	O
programs	O
on	O
the	O
same	O
system	O
or	O
platform	O
that	O
is	O
performing	O
AES	B-Algorithm
.	O
</s>
<s>
In	O
December	O
2009	O
an	O
attack	O
on	O
some	O
hardware	O
implementations	O
was	O
published	O
that	O
used	O
differential	B-General_Concept
fault	I-General_Concept
analysis	I-General_Concept
and	O
allows	O
recovery	O
of	O
a	O
key	O
with	O
a	O
complexity	O
of	O
232	O
.	O
</s>
<s>
In	O
November	O
2010	O
Endre	O
Bangerter	O
,	O
David	O
Gullasch	O
and	O
Stephan	O
Krenn	O
published	O
a	O
paper	O
which	O
described	O
a	O
practical	O
approach	O
to	O
a	O
"	O
near	O
real	O
time	O
"	O
recovery	O
of	O
secret	O
keys	O
from	O
AES-128	B-Algorithm
without	O
the	O
need	O
for	O
either	O
cipher	B-Application
text	O
or	O
plaintext	O
.	O
</s>
<s>
The	O
approach	O
also	O
works	O
on	O
AES-128	B-Algorithm
implementations	O
that	O
use	O
compression	O
tables	O
,	O
such	O
as	O
OpenSSL	B-Language
.	O
</s>
<s>
Like	O
some	O
earlier	O
attacks	O
,	O
this	O
one	O
requires	O
the	O
ability	O
to	O
run	O
unprivileged	O
code	O
on	O
the	O
system	O
performing	O
the	O
AES	B-Algorithm
encryption	I-Algorithm
,	O
which	O
may	O
be	O
achieved	O
by	O
malware	O
infection	O
far	O
more	O
easily	O
than	O
commandeering	O
the	O
root	O
account	O
.	O
</s>
<s>
In	O
March	O
2016	O
,	O
Ashokkumar	O
C.	O
,	O
Ravi	O
Prakash	O
Giri	O
and	O
Bernard	O
Menezes	O
presented	O
a	O
side-channel	O
attack	O
on	O
AES	B-Algorithm
implementations	O
that	O
can	O
recover	O
the	O
complete	O
128-bit	O
AES	B-Algorithm
key	I-Algorithm
in	O
just	O
6	O
–	O
7	O
blocks	O
of	O
plaintext/ciphertext	O
,	O
which	O
is	O
a	O
substantial	O
improvement	O
over	O
previous	O
works	O
that	O
require	O
between	O
100	O
and	O
a	O
million	O
encryptions	O
.	O
</s>
<s>
Many	O
modern	O
CPUs	O
have	O
built-in	O
hardware	B-Algorithm
instructions	I-Algorithm
for	I-Algorithm
AES	I-Algorithm
,	O
which	O
protect	O
against	O
timing-related	O
side-channel	O
attacks	O
.	O
</s>
<s>
The	O
Cryptographic	B-General_Concept
Module	I-General_Concept
Validation	I-General_Concept
Program	I-General_Concept
(	O
CMVP	B-General_Concept
)	O
is	O
operated	O
jointly	O
by	O
the	O
United	O
States	O
Government	O
's	O
National	O
Institute	O
of	O
Standards	O
and	O
Technology	O
(	O
NIST	O
)	O
Computer	O
Security	O
Division	O
and	O
the	O
Communications	O
Security	O
Establishment	O
(	O
CSE	O
)	O
of	O
the	O
Government	O
of	O
Canada	O
.	O
</s>
<s>
Although	O
NIST	O
publication	O
197	O
(	O
“	O
FIPS	B-Algorithm
197	I-Algorithm
”	O
)	O
is	O
the	O
unique	O
document	O
that	O
covers	O
the	O
AES	B-Algorithm
algorithm	O
,	O
vendors	O
typically	O
approach	O
the	O
CMVP	B-General_Concept
under	O
FIPS	O
140	O
and	O
ask	O
to	O
have	O
several	O
algorithms	O
(	O
such	O
as	O
Triple	O
DES	B-Algorithm
or	O
SHA1	B-Algorithm
)	O
validated	O
at	O
the	O
same	O
time	O
.	O
</s>
<s>
Therefore	O
,	O
it	O
is	O
rare	O
to	O
find	O
cryptographic	O
modules	O
that	O
are	O
uniquely	O
FIPS	B-Algorithm
197	I-Algorithm
validated	O
and	O
NIST	O
itself	O
does	O
not	O
generally	O
take	O
the	O
time	O
to	O
list	O
FIPS	B-Algorithm
197	I-Algorithm
validated	O
modules	O
separately	O
on	O
its	O
public	O
web	O
site	O
.	O
</s>
<s>
Instead	O
,	O
FIPS	B-Algorithm
197	I-Algorithm
validation	O
is	O
typically	O
just	O
listed	O
as	O
an	O
"	O
FIPS	O
approved	O
:	O
AES	B-Algorithm
"	O
notation	O
(	O
with	O
a	O
specific	O
FIPS	B-Algorithm
197	I-Algorithm
certificate	O
number	O
)	O
in	O
the	O
current	O
list	O
of	O
FIPS	O
140	O
validated	O
cryptographic	O
modules	O
.	O
</s>
<s>
The	O
Cryptographic	O
Algorithm	O
Validation	O
Program	O
(	O
CAVP	B-General_Concept
)	O
allows	O
for	O
independent	O
validation	O
of	O
the	O
correct	O
implementation	O
of	O
the	O
AES	B-Algorithm
algorithm	O
.	O
</s>
<s>
However	O
,	O
successful	O
CAVP	B-General_Concept
validation	O
in	O
no	O
way	O
implies	O
that	O
the	O
cryptographic	O
module	O
implementing	O
the	O
algorithm	O
is	O
secure	O
.	O
</s>
<s>
Test	O
vectors	O
are	O
a	O
set	O
of	O
known	O
ciphers	B-Application
for	O
a	O
given	O
input	O
and	O
key	O
.	O
</s>
<s>
NIST	O
distributes	O
the	O
reference	O
of	O
AES	B-Algorithm
test	O
vectors	O
as	O
AES	B-Algorithm
Known	O
Answer	O
Test	O
(	O
KAT	O
)	O
Vectors	O
.	O
</s>
<s>
High	O
speed	O
and	O
low	O
RAM	O
requirements	O
were	O
some	O
of	O
the	O
criteria	O
of	O
the	O
AES	B-Algorithm
selection	O
process	O
.	O
</s>
<s>
As	O
the	O
chosen	O
algorithm	O
,	O
AES	B-Algorithm
performed	O
well	O
on	O
a	O
wide	O
variety	O
of	O
hardware	O
,	O
from	O
8-bit	O
smart	O
cards	O
to	O
high-performance	O
computers	O
.	O
</s>
<s>
On	O
a	O
Pentium	B-Device
Pro	I-Device
,	O
AES	B-Algorithm
encryption	I-Algorithm
requires	O
18	O
clock	O
cycles	O
per	O
byte	O
,	O
equivalent	O
to	O
a	O
throughput	O
of	O
about	O
11MiB/s	O
for	O
a	O
200MHz	O
processor	O
.	O
</s>
<s>
On	O
Intel	B-Device
Core	I-Device
and	O
AMD	O
Ryzen	O
CPUs	O
supporting	O
AES-NI	B-Algorithm
instruction	I-Algorithm
set	I-Algorithm
extensions	O
,	O
throughput	O
can	O
be	O
multiple	O
GiB/s	O
(	O
even	O
over	O
15GiB/s	O
on	O
an	O
i7-12700k	O
)	O
.	O
</s>
