<s>
In	O
cryptography	O
,	O
Combined	O
Elliptic-Curve	O
and	O
Post-Quantum	O
2	O
(	O
CECPQ2	B-Protocol
)	O
is	O
a	O
quantum	O
secure	O
modification	O
to	O
Transport	B-Protocol
Layer	I-Protocol
Security	I-Protocol
(	O
TLS	O
)	O
1.3	O
developed	O
by	O
Google	B-Application
.	I-Application
</s>
<s>
Similarly	O
to	O
its	O
predecessor	O
CECPQ1	B-Protocol
,	O
CECPQ2	B-Protocol
aims	O
to	O
provide	O
confidentiality	O
against	O
an	O
attacker	O
with	O
a	O
large	O
scale	O
quantum	B-Architecture
computer	I-Architecture
.	O
</s>
<s>
It	O
is	O
essentially	O
a	O
plugin	O
for	O
the	O
TLS	O
key-agreement	B-Protocol
part	O
.	O
</s>
<s>
CECPQ2	B-Protocol
combines	O
two	O
key	O
exchange	O
mechanisms	O
:	O
the	O
classical	O
X25519	B-Application
and	O
HRSS	O
(	O
Hülsing	O
,	O
Rijneveld	O
,	O
Schanck	O
,	O
and	O
Schwabe	O
)	O
scheme	O
(	O
an	O
instantiation	O
of	O
the	O
NTRU	O
lattice	O
based	O
key	O
exchange	O
primitive	O
)	O
.	O
</s>
<s>
Similarly	O
to	O
CECPQ2	B-Protocol
,	O
this	O
is	O
also	O
a	O
hybrid	O
post-quantum	O
key	O
exchange	O
scheme	O
,	O
that	O
is	O
based	O
on	O
supersingular	B-Algorithm
isogeny	I-Algorithm
key	I-Algorithm
exchange	I-Algorithm
(	O
SIKE	B-Algorithm
)	O
instead	O
of	O
HRSS	O
.	O
</s>
<s>
CECPQ2	B-Protocol
uses	O
32	O
bytes	O
of	O
shared	O
secret	O
material	O
derived	O
from	O
the	O
classical	O
X25519	B-Application
mechanism	O
,	O
and	O
32	O
bytes	O
of	O
shared	O
secret	O
material	O
derived	O
from	O
the	O
quantum-secure	O
HRSS	O
mechanism	O
.	O
</s>
<s>
Concatenation	O
is	O
meant	O
to	O
assure	O
that	O
the	O
protocol	O
provides	O
at	O
least	O
the	O
same	O
security	O
level	O
as	O
widely	O
used	O
X25519	B-Application
,	O
should	O
HRSS	O
be	O
found	O
insecure	O
.	O
</s>
<s>
The	O
algorithm	O
was	O
to	O
be	O
deployed	O
on	O
both	O
the	O
server	O
side	O
using	O
Cloudflare	B-Application
's	O
infrastructure	O
,	O
and	O
the	O
client	O
side	O
using	O
Google	B-Application
Chrome	I-Application
Canary	O
.	O
</s>
<s>
Since	O
both	O
parties	O
need	O
to	O
support	O
the	O
algorithm	O
for	O
it	O
to	O
be	O
chosen	O
,	O
this	O
experiment	O
is	O
available	O
only	O
to	O
Chrome	B-Application
Canary	O
users	O
accessing	O
websites	O
hosted	O
by	O
Cloudflare	B-Application
.	O
</s>
<s>
It	O
was	O
considered	O
a	O
step	O
in	O
a	O
general	O
program	O
at	O
Cloudflare	B-Application
to	O
transition	O
to	O
post-quantum	O
safe	O
cryptographic	O
primitives	O
.	O
</s>
