<s>
VEST	B-Algorithm
(	O
Very	O
Efficient	O
Substitution	O
Transposition	B-Algorithm
)	O
ciphers	B-Application
are	O
a	O
set	O
of	O
families	O
of	O
general-purpose	O
hardware-dedicated	O
ciphers	B-Application
that	O
support	O
single	O
pass	O
authenticated	B-Algorithm
encryption	I-Algorithm
and	O
can	O
operate	O
as	O
collision-resistant	B-Algorithm
hash	I-Algorithm
functions	I-Algorithm
designed	O
by	O
Sean	O
O'Neil	O
,	O
Benjamin	O
Gittins	O
and	O
Howard	O
Landman	O
.	O
</s>
<s>
VEST	B-Algorithm
cannot	O
be	O
implemented	O
efficiently	O
in	O
software	O
.	O
</s>
<s>
VEST	B-Algorithm
is	O
based	O
on	O
a	O
balanced	O
T-function	O
that	O
can	O
also	O
be	O
described	O
as	O
a	O
bijective	B-Algorithm
nonlinear	B-Algorithm
feedback	I-Algorithm
shift	I-Algorithm
register	I-Algorithm
with	O
parallel	O
feedback	O
(	O
NLPFSR	B-Algorithm
)	O
or	O
as	O
a	O
substitution	B-Algorithm
–	I-Algorithm
permutation	I-Algorithm
network	I-Algorithm
,	O
which	O
is	O
assisted	O
by	O
a	O
non-linear	O
RNS-based	O
counter	O
.	O
</s>
<s>
The	O
four	O
VEST	B-Algorithm
family	O
trees	O
described	O
in	O
the	O
cipher	B-Application
specification	O
are	O
VEST-4	O
,	O
VEST-8	O
,	O
VEST-16	O
,	O
and	O
VEST-32	O
.	O
</s>
<s>
VEST	B-Algorithm
ciphers	B-Application
support	O
keys	O
and	O
IVs	O
of	O
variable	O
sizes	O
and	O
instant	O
re-keying	O
.	O
</s>
<s>
All	O
VEST	B-Algorithm
ciphers	B-Application
release	O
output	O
on	O
every	O
clock	O
cycle	O
.	O
</s>
<s>
All	O
the	O
VEST	B-Algorithm
variants	O
are	O
covered	O
by	O
European	O
Patent	O
Number	O
,	O
owned	O
by	O
Synaptic	O
Laboratories	O
.	O
</s>
<s>
VEST	B-Algorithm
was	O
a	O
Phase	O
2	O
Candidate	O
in	O
the	O
eSTREAM	O
competition	O
in	O
the	O
hardware	O
portfolio	O
,	O
but	O
was	O
not	O
a	O
Phase	O
3	O
or	O
Focus	O
candidate	O
and	O
so	O
is	O
not	O
part	O
of	O
the	O
final	O
portfolio	O
.	O
</s>
<s>
VEST	B-Algorithm
ciphers	B-Application
consist	O
of	O
four	O
components	O
:	O
a	O
non-linear	O
counter	O
,	O
a	O
linear	O
counter	O
diffusor	O
,	O
a	O
bijective	B-Algorithm
non-linear	O
accumulator	O
with	O
a	O
large	O
state	O
and	O
a	O
linear	O
output	O
combiner	O
(	O
as	O
illustrated	O
by	O
the	O
image	O
on	O
the	O
top-right	O
corner	O
of	O
this	O
page	O
)	O
.	O
</s>
<s>
The	O
RNS	B-Architecture
counter	O
consists	O
of	O
sixteen	O
NLFSRs	B-Algorithm
with	O
prime	O
periods	O
,	O
the	O
counter	O
diffusor	O
is	O
a	O
set	O
of	O
5-to-1	O
linear	O
combiners	O
with	O
feedback	O
compressing	O
outputs	O
of	O
the	O
16	O
counters	O
into	O
10	O
bits	O
while	O
at	O
the	O
same	O
time	O
expanding	O
the	O
8	O
data	O
inputs	O
into	O
9	O
bits	O
,	O
the	O
core	O
accumulator	O
is	O
an	O
NLPFSR	B-Algorithm
accepting	O
10	O
bits	O
of	O
the	O
counter	O
diffusor	O
as	O
its	O
input	O
,	O
and	O
the	O
output	O
combiner	O
is	O
a	O
set	O
of	O
6-to-1	O
linear	O
combiners	O
.	O
</s>
<s>
The	O
core	O
accumulator	O
in	O
VEST	B-Algorithm
ciphers	B-Application
can	O
be	O
seen	O
as	O
a	O
SPN	B-Algorithm
constructed	O
using	O
non-linear	O
6-to-1	O
feedback	O
functions	O
,	O
one	O
for	O
each	O
bit	O
,	O
all	O
of	O
which	O
are	O
updated	O
simultaneously	O
.	O
</s>
<s>
The	O
VEST-4	O
core	O
accumulator	O
is	O
illustrated	O
below	O
:	O
</s>
<s>
The	O
least	O
significant	O
five	O
bits	O
(	O
p0p4	O
)	O
in	O
the	O
accumulator	O
state	O
are	O
updated	O
by	O
a	O
5×5	O
substitution	B-Algorithm
box	I-Algorithm
and	O
linearly	O
combined	O
with	O
the	O
first	O
five	O
input	O
bits	O
on	O
each	O
round	O
.	O
</s>
<s>
In	O
authenticated	B-Algorithm
encryption	I-Algorithm
mode	O
,	O
the	O
ciphertext	O
feedback	O
bits	O
are	O
also	O
linearly	O
fed	O
back	O
into	O
the	O
accumulator	O
(	O
e0e3	O
)	O
with	O
a	O
non-linear	O
function	O
of	O
four	O
of	O
the	O
less	O
significant	O
accumulator	O
bits	O
.	O
</s>
<s>
All	O
the	O
other	O
bits	O
in	O
the	O
VEST	B-Algorithm
accumulator	O
state	O
are	O
linearly	O
combined	O
with	O
non-linear	O
functions	O
of	O
five	O
less	O
significant	O
bits	O
of	O
the	O
accumulator	O
state	O
on	O
each	O
round	O
.	O
</s>
<s>
The	O
use	O
of	O
only	O
the	O
less	O
significant	O
bits	O
as	O
inputs	O
into	O
the	O
feedback	O
functions	O
for	O
each	O
bit	O
is	O
typical	O
of	O
T-functions	O
and	O
is	O
responsible	O
for	O
the	O
feedback	O
bijectivity	B-Algorithm
.	O
</s>
<s>
This	O
substitution	O
operation	O
is	O
followed	O
by	O
a	O
pseudorandom	B-Error_Name
transposition	B-Algorithm
of	O
all	O
the	O
bits	O
in	O
the	O
state	O
(	O
see	O
picture	O
below	O
)	O
.	O
</s>
<s>
VEST	B-Algorithm
ciphers	B-Application
can	O
be	O
executed	O
in	O
their	O
native	O
authenticated	B-Algorithm
encryption	I-Algorithm
mode	O
similar	O
to	O
that	O
of	O
Phelix	B-Algorithm
but	O
authenticating	O
ciphertext	O
rather	O
than	O
plaintext	O
at	O
the	O
same	O
speed	O
and	O
occupying	O
the	O
same	O
area	O
as	O
keystream	B-Algorithm
generation	O
.	O
</s>
<s>
The	O
four	O
root	O
VEST	B-Algorithm
cipher	B-Application
families	O
are	O
referred	O
to	O
as	O
VEST-4	O
,	O
VEST-8	O
,	O
VEST-16	O
,	O
and	O
VEST-32	O
.	O
</s>
<s>
Each	O
of	O
the	O
four	O
family	O
trees	O
of	O
VEST	B-Algorithm
ciphers	B-Application
supports	O
family	O
keying	O
to	O
generate	O
other	O
independent	O
cipher	B-Application
families	O
of	O
the	O
same	O
size	O
.	O
</s>
<s>
The	O
family-keying	O
process	O
is	O
a	O
standard	O
method	O
to	O
generate	O
cipher	B-Application
families	O
with	O
unique	O
substitutions	O
and	O
unique	O
counters	O
with	O
different	O
periods	O
.	O
</s>
<s>
Family	O
keying	O
enables	O
the	O
end-user	O
to	O
generate	O
a	O
unique	O
secure	O
cipher	B-Application
for	O
every	O
chip	O
.	O
</s>
<s>
VEST	B-Algorithm
ciphers	B-Application
are	O
assisted	O
by	O
a	O
non-linear	O
RNS	B-Architecture
counter	O
with	O
a	O
very	O
long	O
period	O
.	O
</s>
<s>
According	O
to	O
the	O
authors	O
,	O
determining	O
average	O
periods	O
of	O
VEST	B-Algorithm
ciphers	B-Application
or	O
probabilities	O
of	O
the	O
shortest	O
periods	O
of	O
VEST-16	O
and	O
VEST-32	O
falling	O
below	O
their	O
advertised	O
security	O
ratings	O
for	O
some	O
keys	O
remains	O
an	O
open	O
problem	O
and	O
is	O
computationally	O
infeasible	O
.	O
</s>
<s>
They	O
believe	O
that	O
these	O
probabilities	O
are	O
below	O
2−160	O
for	O
VEST-16	O
and	O
below	O
2−256	O
for	O
VEST-32	O
.	O
</s>
<s>
The	O
shortest	O
theoretically	O
possible	O
periods	O
of	O
VEST-4	O
and	O
VEST-8	O
are	O
above	O
their	O
security	O
ratings	O
as	O
can	O
be	O
seen	O
from	O
the	O
following	O
table	O
.	O
</s>
<s>
The	O
core	O
accumulator	O
in	O
VEST	B-Algorithm
ciphers	B-Application
has	O
a	O
complex	O
,	O
highly	O
irregular	O
structure	O
that	O
resists	O
its	O
efficient	O
implementation	O
in	O
software	O
.	O
</s>
<s>
The	O
large	O
differential	O
between	O
VEST	B-Algorithm
's	O
optimised	O
hardware	O
execution	O
and	O
equivalently	O
clocked	O
software	O
optimised	O
execution	O
offers	O
a	O
natural	O
resistance	O
against	O
low	O
cost	O
general-purpose	O
software	O
processor	O
clones	O
masquerading	O
as	O
genuine	O
hardware	O
authentication	O
tokens	O
.	O
</s>
<s>
In	O
bulk	O
challenge-response	O
scenarios	O
such	O
as	O
RFID	O
authentication	O
applications	O
,	O
bitsliced	O
implementations	O
of	O
VEST	B-Algorithm
ciphers	B-Application
on	O
32-bit	O
processors	O
which	O
process	O
many	O
independent	O
messages	O
simultaneously	O
are	O
2	O
–	O
4	O
times	O
slower	O
per	O
message	O
byte	O
than	O
AES	O
.	O
</s>
<s>
VEST	B-Algorithm
is	O
submitted	O
to	O
the	O
eStream	O
competition	O
under	O
the	O
Profile	O
II	O
as	O
designed	O
for	O
"	O
hardware	O
applications	O
with	O
restricted	O
resources	O
such	O
as	O
limited	O
storage	O
,	O
gate	O
count	O
,	O
or	O
power	O
consumption	O
"	O
,	O
and	O
shows	O
high	O
speeds	O
in	O
FPGA	B-Architecture
and	O
ASIC	O
hardware	O
according	O
to	O
.	O
</s>
<s>
The	O
authors	O
claim	O
that	O
according	O
to	O
their	O
own	O
implementations	O
using	O
"	O
conservative	O
standard	O
RapidChip	O
design	O
front-end	O
sign-off	O
process	O
"	O
,	O
"	O
VEST-32	O
can	O
effortlessly	O
satisfy	O
a	O
demand	O
for	O
256-bit	O
secure	O
10	O
Gbit/s	O
authenticated	B-Algorithm
encryption	I-Algorithm
@	O
167	O
MHz	O
on	O
180ηm	O
LSI	O
Logic	O
RapidChip	O
platform	O
ASIC	O
technologies	O
in	O
less	O
than	O
45K	O
Gates	O
and	O
zero	O
SRAM	O
"	O
.	O
</s>
<s>
On	O
the	O
110ηm	O
Rapidchip	O
technologies	O
,	O
VEST-32	O
offers	O
20	O
Gbit/s	O
authenticated	B-Algorithm
encryption	I-Algorithm
@	O
320MHz	O
in	O
less	O
than	O
45	O
K	O
gates	O
"	O
.	O
</s>
<s>
They	O
also	O
state	O
that	O
unrolling	O
the	O
round	O
function	O
of	O
VEST	B-Algorithm
can	O
halve	O
the	O
clock-speed	O
and	O
reduce	O
power	O
consumption	O
while	O
doubling	O
the	O
output	O
per	O
clock-cycle	O
,	O
at	O
the	O
cost	O
of	O
increased	O
area	O
.	O
</s>
<s>
VEST	B-Algorithm
ciphers	B-Application
offer	O
3	O
keying	O
strategies	O
:	O
</s>
<s>
Instantly	O
loading	O
the	O
entire	O
cipher	B-Application
state	O
with	O
a	O
cryptographically	O
strong	O
key	O
(	O
100%	O
entropy	O
)	O
supplied	O
by	O
a	O
strong	O
key	O
generation	O
or	O
key	O
exchange	O
process	O
;	O
</s>
<s>
Instant	O
reloading	O
of	O
the	O
entire	O
cipher	B-Application
state	O
with	O
a	O
previously	O
securely	O
initialised	O
cipher	B-Application
state	O
;	O
</s>
<s>
The	O
entire	O
cipher	B-Application
state	O
can	O
now	O
be	O
stored	O
for	O
instant	O
reloading	O
.	O
</s>
<s>
VEST	B-Algorithm
ciphers	B-Application
offer	O
only	O
1	O
resynchronisation	O
strategy	O
:	O
</s>
<s>
Hashing	O
the	O
(	O
IV	B-Algorithm
)	O
by	O
loading	O
it	O
incrementally	O
8-bits	O
at	O
a	O
time	O
into	O
the	O
first	O
8	O
RNS	B-Architecture
counters	O
,	O
followed	O
by	O
additional	O
32	O
sealing	O
rounds	O
.	O
</s>
<s>
VEST	B-Algorithm
was	O
designed	O
by	O
Sean	O
O'Neil	O
and	O
submitted	O
to	O
the	O
eStream	O
competition	O
in	O
June	O
2005	O
.	O
</s>
<s>
This	O
was	O
the	O
first	O
publication	O
of	O
the	O
cipher	B-Application
.	O
</s>
<s>
The	O
authors	O
say	O
that	O
VEST	B-Algorithm
security	O
margins	O
are	O
inline	O
with	O
the	O
guidelines	O
proposed	O
by	O
Lars	O
Knudsen	O
in	O
the	O
paper	O
"	O
Some	O
thoughts	O
on	O
the	O
AES	O
process	O
"	O
and	O
the	O
more	O
conservative	O
guidelines	O
recently	O
proposed	O
by	O
Nicolas	O
Courtois	O
in	O
the	O
paper	O
“	O
Cryptanalysis	O
of	O
Sfinks	O
”	O
.	O
</s>
<s>
Although	O
the	O
authors	O
are	O
not	O
publishing	O
their	O
own	O
cryptanalysis	O
,	O
VEST	B-Algorithm
ciphers	B-Application
have	O
survived	O
more	O
than	O
a	O
year	O
of	O
public	O
scrutiny	O
as	O
a	O
part	O
of	O
the	O
eStream	O
competition	O
organised	O
by	O
the	O
ECRYPT	O
.	O
</s>
<s>
By	O
comparing	O
the	O
complexity	O
of	O
the	O
attack	O
to	O
a	O
parallelized	O
brute-force	O
attack	O
,	O
Bernstein	O
evaluated	O
the	O
resultant	O
strength	O
of	O
the	O
cipher	B-Application
as	O
100	O
bits	O
,	O
somewhat	O
below	O
the	O
design	O
strength	O
of	O
most	O
of	O
the	O
VEST	B-Algorithm
family	O
members	O
.	O
</s>
<s>
The	O
designers	O
of	O
VEST	B-Algorithm
claimed	O
the	O
attack	O
is	O
due	O
to	O
a	O
typographical	O
error	O
in	O
the	O
original	O
cipher	B-Application
specification	O
and	O
published	O
a	O
correction	O
on	O
the	O
Cryptology	O
ePrint	O
archive	O
on	O
21	O
January	O
2007	O
,	O
a	O
few	O
days	O
prior	O
to	O
publication	O
of	O
the	O
attack	O
.	O
</s>
