<s>
Colossus	B-Device
was	O
a	O
set	O
of	O
computers	O
developed	O
by	O
British	O
codebreakers	O
in	O
the	O
years	O
1943	O
–	O
1945	O
to	O
help	O
in	O
the	O
cryptanalysis	O
of	O
the	O
Lorenz	O
cipher	O
.	O
</s>
<s>
Colossus	B-Device
used	O
thermionic	O
valves	O
(	O
vacuum	O
tubes	O
)	O
to	O
perform	O
Boolean	O
and	O
counting	O
operations	O
.	O
</s>
<s>
Colossus	B-Device
is	O
thus	O
regarded	O
as	O
the	O
world	O
's	O
first	O
programmable	B-General_Concept
,	O
electronic	O
,	O
digital	O
computer	O
,	O
although	O
it	O
was	O
programmed	B-General_Concept
by	O
switches	O
and	O
plugs	O
and	O
not	O
by	O
a	O
stored	O
program	O
.	O
</s>
<s>
Colossus	B-Device
was	O
designed	O
by	O
General	O
Post	O
Office	O
(	O
GPO	O
)	O
research	O
telephone	O
engineer	O
Tommy	O
Flowers	O
to	O
solve	O
a	O
problem	O
posed	O
by	O
mathematician	O
Max	O
Newman	O
at	O
the	O
Government	O
Code	O
and	O
Cypher	O
School	O
(	O
GC&CS	O
)	O
at	O
Bletchley	O
Park	O
.	O
</s>
<s>
It	O
has	O
sometimes	O
been	O
erroneously	O
stated	O
that	O
Turing	O
designed	O
Colossus	B-Device
to	O
aid	O
the	O
cryptanalysis	O
of	O
the	O
Enigma	O
.	O
</s>
<s>
(	O
Turing	O
's	O
machine	O
that	O
helped	O
decode	O
Enigma	O
was	O
the	O
electromechanical	O
Bombe	B-Device
,	O
not	O
Colossus	B-Device
.	O
)	O
</s>
<s>
The	O
prototype	O
,	O
Colossus	B-Device
Mark	O
1	O
,	O
was	O
shown	O
to	O
be	O
working	O
in	O
December	O
1943	O
and	O
was	O
in	O
use	O
at	O
Bletchley	O
Park	O
by	O
early	O
1944	O
.	O
</s>
<s>
An	O
improved	O
Colossus	B-Device
Mark	O
2	O
that	O
used	O
shift	B-General_Concept
registers	I-General_Concept
to	O
quintuple	O
the	O
processing	O
speed	O
,	O
first	O
worked	O
on	O
1	O
June	O
1944	O
,	O
just	O
in	O
time	O
for	O
the	O
Normandy	O
landings	O
on	O
D-Day	O
.	O
</s>
<s>
The	O
existence	O
of	O
the	O
Colossus	B-Device
machines	O
was	O
kept	O
secret	O
until	O
the	O
mid-1970s	O
.	O
</s>
<s>
A	O
functioning	O
rebuild	O
of	O
a	O
Mark	O
2	O
Colossus	B-Device
was	O
completed	O
in	O
2008	O
by	O
Tony	O
Sale	O
and	O
a	O
team	O
of	O
volunteers	O
;	O
it	O
is	O
on	O
display	O
at	O
The	O
National	O
Museum	O
of	O
Computing	O
on	O
Bletchley	O
Park	O
.	O
</s>
<s>
The	O
Colossus	B-Device
computers	I-Device
were	O
used	O
to	O
help	O
decipher	O
intercepted	O
radio	O
teleprinter	O
messages	O
that	O
had	O
been	O
encrypted	O
using	O
an	O
unknown	O
device	O
.	O
</s>
<s>
It	O
did	O
this	O
by	O
combining	O
the	O
plaintext	O
characters	O
with	O
a	O
stream	O
of	O
key	O
characters	O
using	O
the	O
XOR	B-Application
Boolean	O
function	O
to	O
produce	O
the	O
ciphertext	O
.	O
</s>
<s>
First	O
,	O
John	O
Tiltman	O
,	O
a	O
very	O
talented	O
GC&CS	O
cryptanalyst	O
,	O
derived	O
a	O
key	B-Algorithm
stream	I-Algorithm
of	O
almost	O
4000	O
characters	O
.	O
</s>
<s>
Then	O
Bill	O
Tutte	O
,	O
a	O
newly	O
arrived	O
member	O
of	O
the	O
Research	O
Section	O
,	O
used	O
this	O
keystream	B-Algorithm
to	O
work	O
out	O
the	O
logical	O
structure	O
of	O
the	O
Lorenz	O
machine	O
.	O
</s>
<s>
With	O
a	O
sufficiently	O
random	O
keystream	B-Algorithm
,	O
a	O
Vernam	B-Algorithm
cipher	I-Algorithm
removes	O
the	O
natural	O
language	O
property	O
of	O
a	O
plaintext	O
message	O
of	O
having	O
an	O
uneven	O
frequency	O
distribution	O
of	O
the	O
different	O
characters	O
,	O
to	O
produce	O
a	O
uniform	O
distribution	O
in	O
the	O
ciphertext	O
.	O
</s>
<s>
This	O
was	O
achieved	O
by	O
"	O
differencing	O
"	O
in	O
which	O
each	O
bit	O
or	O
character	O
was	O
XOR-ed	O
with	O
its	O
successor	O
.	O
</s>
<s>
The	O
first	O
was	O
"	O
wheel	O
breaking	O
"	O
,	O
which	O
was	O
the	O
discovery	O
of	O
the	O
cam	B-Data_Structure
patterns	O
for	O
all	O
the	O
wheels	O
.	O
</s>
<s>
Turing	O
's	O
technique	O
was	O
further	O
developed	O
into	O
"	O
Rectangling	O
"	O
,	O
for	O
which	O
Colossus	B-Device
could	O
produce	O
tables	O
for	O
manual	O
analysis	O
.	O
</s>
<s>
The	O
second	O
task	O
was	O
"	O
wheel	O
setting	O
"	O
,	O
which	O
worked	O
out	O
the	O
start	O
positions	O
of	O
the	O
wheels	O
for	O
a	O
particular	O
message	O
and	O
could	O
only	O
be	O
attempted	O
once	O
the	O
cam	B-Data_Structure
patterns	O
were	O
known	O
.	O
</s>
<s>
It	O
was	O
this	O
task	O
for	O
which	O
Colossus	B-Device
was	O
initially	O
designed	O
.	O
</s>
<s>
To	O
discover	O
the	O
start	O
position	O
of	O
the	O
chi	O
wheels	O
for	O
a	O
message	O
,	O
Colossus	B-Device
compared	O
two	O
character	O
streams	O
,	O
counting	O
statistics	O
from	O
the	O
evaluation	O
of	O
programmable	B-General_Concept
Boolean	O
functions	O
.	O
</s>
<s>
The	O
two	O
streams	O
were	O
the	O
ciphertext	O
,	O
which	O
was	O
read	O
at	O
high	O
speed	O
from	O
a	O
paper	O
tape	O
,	O
and	O
the	O
keystream	B-Algorithm
,	O
which	O
was	O
generated	O
internally	O
,	O
in	O
a	O
simulation	O
of	O
the	O
unknown	O
German	O
machine	O
.	O
</s>
<s>
After	O
a	O
succession	O
of	O
different	O
Colossus	B-Device
runs	O
to	O
discover	O
the	O
likely	O
chi-wheel	O
settings	O
,	O
they	O
were	O
checked	O
by	O
examining	O
the	O
frequency	O
distribution	O
of	O
the	O
characters	O
in	O
the	O
processed	O
ciphertext	O
.	O
</s>
<s>
Colossus	B-Device
produced	O
these	O
frequency	O
counts	O
.	O
</s>
<s>
Colossus	B-Device
could	O
also	O
derive	O
the	O
start	O
position	O
of	O
the	O
psi	O
and	O
motor	O
wheels	O
,	O
but	O
this	O
was	O
not	O
much	O
done	O
until	O
the	O
last	O
few	O
months	O
of	O
the	O
war	O
when	O
there	O
were	O
plenty	O
of	O
Colossi	O
available	O
and	O
the	O
number	O
of	O
Tunny	O
messages	O
had	O
declined	O
.	O
</s>
<s>
Colossus	B-Device
was	O
developed	O
for	O
the	O
"	O
Newmanry	O
"	O
,	O
the	O
section	O
headed	O
by	O
the	O
mathematician	O
Max	O
Newman	O
that	O
was	O
responsible	O
for	O
machine	O
methods	O
against	O
the	O
twelve-rotor	O
Lorenz	O
SZ40/42	O
on-line	O
teleprinter	O
cipher	O
machine	O
(	O
code-named	O
Tunny	O
,	O
for	O
tunafish	O
)	O
.	O
</s>
<s>
The	O
Colossus	B-Device
design	O
arose	O
out	O
of	O
a	O
prior	O
project	O
that	O
produced	O
a	O
counting	O
machine	O
dubbed	O
"	O
Heath	O
Robinson	O
"	O
.	O
</s>
<s>
The	O
electro-mechanical	O
parts	O
were	O
relatively	O
slow	O
and	O
it	O
was	O
difficult	O
to	O
synchronise	O
two	O
looped	O
paper	O
tapes	O
,	O
one	O
containing	O
the	O
enciphered	O
message	O
,	O
and	O
the	O
other	O
representing	O
part	O
of	O
the	O
keystream	B-Algorithm
of	O
the	O
Lorenz	O
machine	O
,	O
also	O
the	O
tapes	O
tended	O
to	O
stretch	O
when	O
being	O
read	O
at	O
up	O
to	O
2000	O
characters	O
per	O
second	O
.	O
</s>
<s>
Prior	O
to	O
his	O
work	O
on	O
Colossus	B-Device
,	O
he	O
had	O
been	O
involved	O
with	O
GC&CS	O
at	O
Bletchley	O
Park	O
from	O
February	O
1941	O
in	O
an	O
attempt	O
to	O
improve	O
the	O
Bombes	B-Device
that	O
were	O
used	O
in	O
the	O
cryptanalysis	O
of	O
the	O
German	O
Enigma	O
cipher	O
machine	O
.	O
</s>
<s>
He	O
was	O
recommended	O
to	O
Max	O
Newman	O
by	O
Alan	O
Turing	O
,	O
who	O
had	O
been	O
impressed	O
by	O
his	O
work	O
on	O
the	O
Bombes	B-Device
.	O
</s>
<s>
This	O
prototype	O
,	O
Mark	O
1	O
Colossus	B-Device
,	O
contained	O
1,600	O
thermionic	O
valves	O
(	O
tubes	O
)	O
.	O
</s>
<s>
It	O
was	O
a	O
large	O
structure	O
and	O
was	O
dubbed	O
'	O
Colossus	B-Device
 '	O
,	O
supposedly	O
by	O
the	O
WRNS	O
operators	O
.	O
</s>
<s>
However	O
,	O
a	O
memo	O
held	O
in	O
the	O
National	O
Archives	O
written	O
by	O
Max	O
Newman	O
on	O
18	O
January	O
1944	O
records	O
that	O
'	O
Colossus	B-Device
arrives	O
today	O
"	O
.	O
</s>
<s>
During	O
the	O
development	O
of	O
the	O
prototype	O
,	O
an	O
improved	O
design	O
had	O
been	O
developed	O
–	O
the	O
Mark	O
2	O
Colossus	B-Device
.	O
</s>
<s>
A	O
six	O
character	O
FIFO	B-Operating_System
shift	B-General_Concept
register	I-General_Concept
.	O
</s>
<s>
Most	O
of	O
the	O
design	O
of	O
the	O
electronics	O
was	O
the	O
work	O
of	O
Tommy	O
Flowers	O
,	O
assisted	O
by	O
William	O
Chandler	O
,	O
Sidney	O
Broadhurst	O
and	O
Allen	O
Coombs	O
;	O
with	O
Erie	O
Speight	O
and	O
Arnold	O
Lynch	O
developing	O
the	O
photoelectric	B-Algorithm
reading	O
mechanism	O
.	O
</s>
<s>
Data	O
input	O
to	O
Colossus	B-Device
was	O
by	O
photoelectric	B-Algorithm
reading	O
of	O
a	O
paper	O
tape	O
transcription	O
of	O
the	O
enciphered	O
intercepted	O
message	O
.	O
</s>
<s>
Flowers	O
designed	O
a	O
6-character	O
shift	B-General_Concept
register	I-General_Concept
,	O
which	O
was	O
used	O
both	O
for	O
computing	O
the	O
delta	O
function	O
( ΔZ	O
)	O
and	O
for	O
testing	O
five	O
different	O
possible	O
starting	O
points	O
of	O
Tunny	O
's	O
wheels	O
in	O
the	O
five	O
processors	O
.	O
</s>
<s>
The	O
first	O
job	O
in	O
operating	O
Colossus	B-Device
for	O
a	O
new	O
message	O
was	O
to	O
prepare	O
the	O
paper	O
tape	O
loop	O
.	O
</s>
<s>
Howard	O
Campaigne	O
,	O
a	O
mathematician	O
and	O
cryptanalyst	O
from	O
the	O
US	O
Navy	O
's	O
OP-20-G	O
,	O
wrote	O
the	O
following	O
in	O
a	O
foreword	O
to	O
Flowers	O
 '	O
1983	O
paper	O
"	O
The	O
Design	O
of	O
Colossus	B-Device
"	O
.	O
</s>
<s>
Colossus	B-Device
was	O
not	O
a	O
stored-program	O
computer	O
.	O
</s>
<s>
Input	O
to	O
the	O
processors	O
came	O
from	O
two	O
sources	O
,	O
the	O
shift	B-General_Concept
registers	I-General_Concept
from	O
tape	O
reading	O
and	O
the	O
thyratron	O
rings	O
that	O
emulated	O
the	O
wheels	O
of	O
the	O
Tunny	O
machine	O
.	O
</s>
<s>
Although	O
the	O
Colossus	B-Device
was	O
the	O
first	O
of	O
the	O
electronic	O
digital	O
machines	O
with	O
programmability	O
,	O
albeit	O
limited	O
by	O
modern	O
standards	O
,	O
it	O
was	O
not	O
a	O
general-purpose	O
machine	O
,	O
being	O
designed	O
for	O
a	O
range	O
of	O
cryptanalytic	O
tasks	O
,	O
most	O
involving	O
counting	O
the	O
results	O
of	O
evaluating	O
Boolean	O
algorithms	O
.	O
</s>
<s>
A	O
Colossus	B-Device
computer	I-Device
was	O
thus	O
not	O
a	O
fully	O
Turing	B-Algorithm
complete	I-Algorithm
machine	O
.	O
</s>
<s>
However	O
,	O
University	O
of	O
San	O
Francisco	O
professor	O
Benjamin	O
Wells	O
has	O
shown	O
that	O
if	O
all	O
ten	O
Colossus	B-Device
machines	O
made	O
were	O
rearranged	O
in	O
a	O
specific	O
cluster	B-Architecture
,	O
then	O
the	O
entire	O
set	O
of	O
computers	O
could	O
have	O
simulated	O
a	O
universal	O
Turing	O
machine	O
,	O
and	O
thus	O
be	O
Turing	B-Algorithm
complete	I-Algorithm
.	O
</s>
<s>
Colossus	B-Device
and	O
the	O
reasons	O
for	O
its	O
construction	O
were	O
highly	O
secret	O
and	O
remained	O
so	O
for	O
30	O
years	O
after	O
the	O
War	O
.	O
</s>
<s>
Consequently	O
,	O
it	O
was	O
not	O
included	O
in	O
the	O
history	B-Architecture
of	I-Architecture
computing	I-Architecture
hardware	I-Architecture
for	O
many	O
years	O
,	O
and	O
Flowers	O
and	O
his	O
associates	O
were	O
deprived	O
of	O
the	O
recognition	O
they	O
were	O
due	O
.	O
</s>
<s>
One	O
of	O
the	O
Colossi	O
,	O
known	O
as	O
Colossus	B-Device
Blue	O
,	O
was	O
dismantled	O
in	O
1959	O
;	O
the	O
other	O
in	O
1960	O
.	O
</s>
<s>
Jack	O
Good	O
related	O
how	O
he	O
was	O
the	O
first	O
to	O
use	O
Colossus	B-Device
after	O
the	O
war	O
,	O
persuading	O
the	O
US	O
National	O
Security	O
Agency	O
that	O
it	O
could	O
be	O
used	O
to	O
perform	O
a	O
function	O
for	O
which	O
they	O
were	O
planning	O
to	O
build	O
a	O
special-purpose	O
machine	O
.	O
</s>
<s>
Colossus	B-Device
was	O
also	O
used	O
to	O
perform	O
character	O
counts	O
on	O
one-time	B-Algorithm
pad	I-Algorithm
tape	O
to	O
test	O
for	O
non-randomness	O
.	O
</s>
<s>
A	O
small	O
number	O
of	O
people	O
who	O
were	O
associated	O
with	O
Colossus	B-Device
—	O
and	O
knew	O
that	O
large-scale	O
,	O
reliable	O
,	O
high-speed	O
electronic	O
digital	O
computing	O
devices	O
were	O
feasible	O
—	O
played	O
significant	O
roles	O
in	O
early	O
computer	O
work	O
in	O
the	O
UK	O
and	O
probably	O
in	O
the	O
US	O
.	O
</s>
<s>
However	O
,	O
being	O
so	O
secret	O
,	O
it	O
had	O
little	O
direct	O
influence	O
on	O
the	O
development	O
of	O
later	O
computers	O
;	O
it	O
was	O
EDVAC	B-Device
that	O
was	O
the	O
seminal	O
computer	O
architecture	O
of	O
the	O
time	O
.	O
</s>
<s>
In	O
1972	O
,	O
Herman	O
Goldstine	O
,	O
who	O
was	O
unaware	O
of	O
Colossus	B-Device
and	O
its	O
legacy	O
to	O
the	O
projects	O
of	O
people	O
such	O
as	O
Alan	O
Turing	O
(	O
ACE	B-Device
)	O
,	O
Max	O
Newman	O
(	O
Manchester	B-Device
computers	I-Device
)	O
and	O
Harry	O
Huskey	O
(	O
Bendix	B-Device
G-15	I-Device
)	O
,	O
wrote	O
that	O
,	O
</s>
<s>
Professor	O
Brian	O
Randell	O
,	O
who	O
unearthed	O
information	O
about	O
Colossus	B-Device
in	O
the	O
1970s	O
,	O
commented	O
on	O
this	O
,	O
saying	O
that	O
:	O
</s>
<s>
Randell	O
was	O
researching	O
the	O
history	B-Architecture
of	I-Architecture
computer	I-Architecture
science	O
in	O
Britain	O
for	O
a	O
conference	O
on	O
the	O
history	O
of	O
computing	O
held	O
at	O
the	O
Los	O
Alamos	O
Scientific	O
Laboratory	O
,	O
New	O
Mexico	O
on	O
10-15	O
June	O
1976	O
,	O
and	O
got	O
permission	O
to	O
present	O
a	O
paper	O
on	O
wartime	O
development	O
of	O
the	O
COLOSSI	O
at	O
the	O
Post	O
Office	O
Research	O
Station	O
,	O
Dollis	O
Hill	O
(	O
in	O
October	O
1975	O
the	O
British	O
Government	O
had	O
released	O
a	O
series	O
of	O
captioned	O
photographs	O
from	O
the	O
Public	O
Record	O
Office	O
)	O
.	O
</s>
<s>
In	O
October	O
2000	O
,	O
a	O
500-page	O
technical	O
report	O
on	O
the	O
Tunny	O
cipher	O
and	O
its	O
cryptanalysis	O
—	O
entitled	O
General	O
Report	O
on	O
Tunny	O
—	O
was	O
released	O
by	O
GCHQ	O
to	O
the	O
national	O
Public	O
Record	O
Office	O
,	O
and	O
it	O
contains	O
a	O
fascinating	O
paean	O
to	O
Colossus	B-Device
by	O
the	O
cryptographers	O
who	O
worked	O
with	O
it	O
:	O
</s>
<s>
Construction	O
of	O
a	O
fully	O
functional	O
rebuild	O
of	O
a	O
Colossus	B-Device
Mark	O
2	O
was	O
undertaken	O
between	O
1993	O
and	O
2008	O
by	O
a	O
team	O
led	O
by	O
Tony	O
Sale	O
.	O
</s>
<s>
The	O
reconstruction	O
is	O
on	O
display	O
,	O
in	O
the	O
historically	O
correct	O
place	O
for	O
Colossus	B-Device
No	O
.	O
</s>
<s>
In	O
November	O
2007	O
,	O
to	O
celebrate	O
the	O
project	O
completion	O
and	O
to	O
mark	O
the	O
start	O
of	O
a	O
fundraising	O
initiative	O
for	O
The	O
National	O
Museum	O
of	O
Computing	O
,	O
a	O
Cipher	O
Challenge	O
pitted	O
the	O
rebuilt	O
Colossus	B-Device
against	O
radio	O
amateurs	O
worldwide	O
in	O
being	O
first	O
to	O
receive	O
and	O
decode	O
three	O
messages	O
enciphered	O
using	O
the	O
Lorenz	O
SZ42	O
and	O
transmitted	O
from	O
radio	O
station	O
DL0HNF	O
in	O
the	O
Heinz	O
Nixdorf	O
MuseumsForum	O
computer	O
museum	O
.	O
</s>
<s>
The	O
challenge	O
was	O
easily	O
won	O
by	O
radio	O
amateur	O
Joachim	O
Schüth	O
,	O
who	O
had	O
carefully	O
prepared	O
for	O
the	O
event	O
and	O
developed	O
his	O
own	O
signal	O
processing	O
and	O
code-breaking	O
code	O
using	O
Ada	B-Language
.	O
</s>
<s>
The	O
Colossus	B-Device
team	O
were	O
hampered	O
by	O
their	O
wish	O
to	O
use	O
World	O
War	O
II	O
radio	O
equipment	O
,	O
delaying	O
them	O
by	O
a	O
day	O
because	O
of	O
poor	O
reception	O
conditions	O
.	O
</s>
<s>
The	O
German	O
codebreaker	O
said	O
:	O
"	O
My	O
laptop	O
digested	O
ciphertext	O
at	O
a	O
speed	O
of	O
1.2million	O
characters	O
per	O
second	O
—	O
240	O
times	O
faster	O
than	O
Colossus	B-Device
.	O
</s>
<s>
If	O
you	O
scale	O
the	O
CPU	O
frequency	O
by	O
that	O
factor	O
,	O
you	O
get	O
an	O
equivalent	O
clock	O
of	O
5.8MHz	O
for	O
Colossus	B-Device
.	O
</s>
<s>
"	O
On	O
the	O
strength	O
of	O
today	O
's	O
performance	O
Colossus	B-Device
is	O
as	O
good	O
as	O
it	O
was	O
six	O
decades	O
ago	O
"	O
,	O
commented	O
Tony	O
Sale	O
.	O
</s>
<s>
There	O
was	O
a	O
fictional	O
computer	O
named	O
Colossus	B-Device
in	O
the	O
1970	O
film	O
Colossus	B-Device
:	O
The	O
Forbin	O
Project	O
which	O
was	O
based	O
on	O
the	O
1966	O
novel	O
Colossus	B-Device
by	O
D	O
.	O
F	O
.	O
Jones	O
.	O
</s>
<s>
This	O
was	O
a	O
coincidence	O
as	O
it	O
pre-dates	O
the	O
public	O
release	O
of	O
information	O
about	O
Colossus	B-Device
,	O
or	O
even	O
its	O
name	O
.	O
</s>
