<s>
A	O
separation	B-Operating_System
kernel	I-Operating_System
is	O
a	O
type	O
of	O
security	O
kernel	B-Operating_System
used	O
to	O
simulate	O
a	O
distributed	O
environment	O
.	O
</s>
<s>
Rushby	O
proposed	O
the	O
separation	B-Operating_System
kernel	I-Operating_System
as	O
a	O
solution	O
to	O
the	O
difficulties	O
and	O
problems	O
that	O
had	O
arisen	O
in	O
the	O
development	O
and	O
verification	O
of	O
large	O
,	O
complex	O
security	O
kernels	B-Operating_System
that	O
were	O
intended	O
to	O
"	O
provide	O
multilevel	O
secure	O
operation	O
on	O
general-purpose	O
multi-user	O
systems.	O
"	O
</s>
<s>
According	O
to	O
Rushby	O
,	O
"	O
the	O
task	O
of	O
a	O
separation	B-Operating_System
kernel	I-Operating_System
is	O
to	O
create	O
an	O
environment	O
which	O
is	O
indistinguishable	O
from	O
that	O
provided	O
by	O
a	O
physically	O
distributed	O
system	O
:	O
it	O
must	O
appear	O
as	O
if	O
each	O
regime	O
is	O
a	O
separate	O
,	O
isolated	O
machine	O
and	O
that	O
information	O
can	O
only	O
flow	O
from	O
one	O
machine	O
to	O
another	O
along	O
known	O
external	O
communication	O
lines	O
.	O
</s>
<s>
One	O
of	O
the	O
properties	O
we	O
must	O
prove	O
of	O
a	O
separation	B-Operating_System
kernel	I-Operating_System
,	O
therefore	O
,	O
is	O
that	O
there	O
are	O
no	O
channels	O
for	O
information	O
flow	O
between	O
regimes	O
other	O
than	O
those	O
explicitly	O
provided.	O
"	O
</s>
<s>
A	O
variant	O
of	O
the	O
separation	B-Operating_System
kernel	I-Operating_System
,	O
the	O
partitioning	O
kernel	B-Operating_System
,	O
has	O
gained	O
acceptance	O
in	O
the	O
commercial	O
aviation	O
community	O
as	O
a	O
way	O
of	O
consolidating	O
,	O
onto	O
a	O
single	O
processor	O
,	O
multiple	O
functions	O
,	O
perhaps	O
of	O
mixed	B-General_Concept
criticality	I-General_Concept
.	O
</s>
<s>
Commercial	O
real-time	B-Operating_System
operating	I-Operating_System
system	I-Operating_System
products	O
in	O
this	O
genre	O
have	O
been	O
used	O
by	O
aircraft	O
manufacturers	O
for	O
safety-critical	O
avionics	O
applications	O
.	O
</s>
<s>
In	O
2007	O
the	O
Information	O
Assurance	O
Directorate	O
of	O
the	O
U.S.	O
National	O
Security	O
Agency	O
(	O
NSA	O
)	O
published	O
the	O
Separation	B-Operating_System
Kernel	I-Operating_System
Protection	O
Profile	O
(	O
SKPP	O
)	O
,	O
a	O
security	O
requirements	O
specification	O
for	O
separation	B-Operating_System
kernels	I-Operating_System
suitable	O
to	O
be	O
used	O
in	O
the	O
most	O
hostile	O
threat	O
environments	O
.	O
</s>
<s>
The	O
SKPP	O
describes	O
,	O
in	O
Common	O
Criteria	O
parlance	O
,	O
a	O
class	O
of	O
modern	O
products	O
that	O
provide	O
the	O
foundational	O
properties	O
of	O
Rushby	O
's	O
conceptual	O
separation	B-Operating_System
kernel	I-Operating_System
.	O
</s>
<s>
It	O
defines	O
the	O
security	O
functional	O
and	O
assurance	O
requirements	O
for	O
the	O
construction	O
and	O
evaluation	O
of	O
separation	B-Operating_System
kernels	I-Operating_System
while	O
yet	O
providing	O
some	O
latitude	O
in	O
the	O
choices	O
available	O
to	O
developers	O
.	O
</s>
<s>
The	O
SKPP	O
defines	O
separation	B-Operating_System
kernel	I-Operating_System
as	O
"	O
hardware	O
and/or	O
firmware	O
and/or	O
software	O
mechanisms	O
whose	O
primary	O
function	O
is	O
to	O
establish	O
,	O
isolate	O
and	O
separate	O
multiple	O
partitions	O
and	O
control	O
information	O
flow	O
between	O
the	O
subjects	O
and	O
exported	O
resources	O
allocated	O
to	O
those	O
partitions.	O
"	O
</s>
<s>
Further	O
,	O
the	O
separation	B-Operating_System
kernel	I-Operating_System
's	O
core	O
functional	O
requirements	O
include	O
:	O
</s>
<s>
Protection	O
of	O
all	O
resources	O
(	O
including	O
CPU	B-General_Concept
,	O
memory	O
and	O
devices	O
)	O
from	O
unauthorized	O
access	O
.	O
</s>
<s>
The	O
separation	B-Operating_System
kernel	I-Operating_System
allocates	O
all	O
exported	O
resources	O
under	O
its	O
control	O
into	O
partitions	O
.	O
</s>
<s>
The	O
separation	B-Operating_System
kernel	I-Operating_System
provides	O
to	O
its	O
hosted	O
software	O
programs	O
high-assurance	O
partitioning	O
and	O
information	O
flow	O
control	O
properties	O
that	O
are	O
both	O
tamperproof	O
and	O
non-bypassable	O
.	O
</s>
<s>
PikeOS	B-Operating_System
combines	O
separation	B-Operating_System
kernel	I-Operating_System
hypervisor	O
technology	O
with	O
hard	O
real-time	O
capabilities	O
.	O
</s>
<s>
INTEGRITY-178B	O
from	O
Green	O
Hills	O
Software	O
In	O
September	O
2008	O
it	O
became	O
the	O
first	O
separation	B-Operating_System
kernel	I-Operating_System
certified	O
against	O
the	O
SKPP	O
.	O
</s>
<s>
Wind	O
River	O
Systems	O
has	O
separation	B-Operating_System
kernel	I-Operating_System
technology	O
that	O
was	O
in	O
active	O
certification	O
process	O
in	O
2009	O
.	O
</s>
<s>
Lynx	B-Operating_System
Software	I-Operating_System
Technologies	I-Operating_System
has	O
a	O
separation	B-Operating_System
kernel	I-Operating_System
,	O
LynxSecure	O
.	O
</s>
<s>
NSA	O
will	O
no	O
longer	O
certify	O
specific	O
operating	O
systems	O
,	O
including	O
separation	B-Operating_System
kernels	I-Operating_System
against	O
the	O
SKPP	O
,	O
noting	O
"	O
conformance	O
to	O
this	O
protection	O
profile	O
,	O
by	O
itself	O
,	O
does	O
not	O
offer	O
sufficient	O
confidence	O
that	O
national	O
security	O
information	O
is	O
appropriately	O
protected	O
in	O
the	O
context	O
of	O
a	O
larger	O
system	O
in	O
which	O
the	O
conformant	O
product	O
is	O
integrated	O
"	O
.	O
</s>
<s>
The	O
seL4	O
microkernel	O
has	O
a	O
formal	O
proof	O
of	O
concept	O
that	O
it	O
can	O
be	O
configured	O
as	O
a	O
separation	B-Operating_System
kernel	I-Operating_System
.	O
</s>
<s>
The	O
Muen	O
separation	B-Operating_System
kernel	I-Operating_System
is	O
also	O
a	O
formally	O
verified	O
open	O
source	O
separation	B-Operating_System
kernel	I-Operating_System
for	O
x86	O
machines	O
.	O
</s>
