<s>
HC-256	B-Algorithm
is	O
a	O
stream	B-Algorithm
cipher	I-Algorithm
designed	O
to	O
provide	O
bulk	B-General_Concept
encryption	I-General_Concept
in	O
software	O
at	O
high	O
speeds	O
while	O
permitting	O
strong	O
confidence	O
in	O
its	O
security	O
.	O
</s>
<s>
HC-256	B-Algorithm
has	O
a	O
256	O
bit	O
key	O
and	O
an	O
initialization	B-Algorithm
vector	I-Algorithm
(	O
nonce	O
)	O
of	O
256	O
bits	O
.	O
</s>
<s>
It	O
generates	O
one	O
32-bit	O
word	O
for	O
each	O
update	O
step	O
using	O
a	O
32-bit	O
to	O
32-bit	O
mapping	O
function	O
similar	O
to	O
the	O
output	O
function	O
of	O
the	O
Blowfish	B-Algorithm
cipher	I-Algorithm
.	O
</s>
<s>
It	O
uses	O
the	O
two	O
message	O
schedule	O
functions	O
in	O
the	O
hash	B-Error_Name
function	I-Error_Name
SHA-256	B-Algorithm
internally	O
,	O
but	O
with	O
the	O
tables	O
P	O
and	O
Q	O
as	O
S-boxes	B-Algorithm
.	O
</s>
<s>
HC-128	B-Algorithm
is	O
similar	O
in	O
function	O
,	O
and	O
reduces	O
each	O
of	O
key	O
length	O
,	O
nonce	O
,	O
number	O
of	O
words	O
in	O
the	O
tables	O
P	O
and	O
Q	O
,	O
and	O
number	O
of	O
table	O
updating	O
steps	O
by	O
half	O
.	O
</s>
<s>
The	O
performance	O
of	O
HC-256	B-Algorithm
is	O
estimated	O
by	O
its	O
author	O
to	O
be	O
about	O
4	O
cycles	O
per	O
byte	O
on	O
a	O
Pentium	B-General_Concept
4	I-General_Concept
processor	O
.	O
</s>
<s>
The	O
author	O
of	O
HC-256	B-Algorithm
estimates	O
this	O
process	O
to	O
take	O
around	O
74,000	O
cycles	O
.	O
</s>
<s>
For	O
HC-128	B-Algorithm
an	O
encryption	O
speed	O
of	O
about	O
3	O
cycles	O
per	O
byte	O
on	O
a	O
Pentium	B-Architecture
M	I-Architecture
processor	O
are	O
cited	O
.	O
</s>
<s>
The	O
implementation	O
of	O
HC-128	B-Algorithm
on	O
various	O
computing	O
structures	O
is	O
studied	O
in	O
detail	O
,	O
with	O
significant	O
performance	O
gains	O
compared	O
to	O
naive	O
SW	O
implementation	O
.	O
</s>
