<s>
Rockex	B-General_Concept
,	O
or	O
Telekrypton	B-General_Concept
,	O
was	O
an	O
offline	O
one-time	B-Algorithm
tape	I-Algorithm
Vernam	B-Algorithm
cipher	I-Algorithm
machine	O
known	O
to	O
have	O
been	O
used	O
by	O
Britain	O
and	O
Canada	O
from	O
1943	O
.	O
</s>
<s>
"	O
Rockex	B-General_Concept
"	O
was	O
named	O
after	O
the	O
Rockefeller	O
Center	O
,	O
together	O
with	O
the	O
tradition	O
for	O
naming	O
British	O
cipher	O
equipment	O
with	O
the	O
suffix	O
"	O
-ex	O
"	O
(	O
e.g.	O
</s>
<s>
In	O
1944	O
an	O
improved	O
Rockex	B-General_Concept
II	O
first	O
appeared	O
.	O
</s>
<s>
After	O
WW2	O
the	O
Rockex	B-General_Concept
machines	O
and	O
the	O
code	O
tapes	O
were	O
manufactured	O
in	O
great	O
secrecy	O
under	O
the	O
control	O
of	O
the	O
Secret	O
Intelligence	O
Service	O
(	O
SIS	O
)	O
,	O
also	O
known	O
as	O
MI6	O
,	O
at	O
a	O
small	O
factory	O
at	O
Number	O
4	O
Chester	O
Road	O
,	O
Borehamwood	O
on	O
the	O
northern	O
outskirts	O
of	O
London	O
.	O
</s>
