<s>
The	O
Secure	B-Protocol
Neighbor	I-Protocol
Discovery	I-Protocol
(	O
SEND	O
)	O
protocol	O
is	O
a	O
security	O
extension	O
of	O
the	O
Neighbor	B-Protocol
Discovery	I-Protocol
Protocol	I-Protocol
(	O
NDP	O
)	O
in	O
IPv6	B-Protocol
defined	O
in	O
RFC	O
3971	O
and	O
updated	O
by	O
RFC	O
6494	O
.	O
</s>
<s>
The	O
Neighbor	B-Protocol
Discovery	I-Protocol
Protocol	I-Protocol
(	O
NDP	O
)	O
is	O
responsible	O
in	O
IPv6	B-Protocol
for	O
discovery	O
of	O
other	O
network	O
nodes	O
on	O
the	O
local	O
link	O
,	O
to	O
determine	O
the	O
link	O
layer	O
addresses	O
of	O
other	O
nodes	O
,	O
and	O
to	O
find	O
available	O
routers	O
,	O
and	O
maintain	O
reachability	O
information	O
about	O
the	O
paths	O
to	O
other	O
active	O
neighbor	O
nodes	O
(	O
RFC	O
4861	O
)	O
.	O
</s>
<s>
It	O
is	O
the	O
intent	O
of	O
SEND	O
to	O
provide	O
an	O
alternate	O
mechanism	O
for	O
securing	O
NDP	O
with	O
a	O
cryptographic	O
method	O
that	O
is	O
independent	O
of	O
IPsec	B-Protocol
,	O
the	O
original	O
and	O
inherent	O
method	O
of	O
securing	O
IPv6	B-Protocol
communications	O
.	O
</s>
<s>
SEND	O
uses	O
Cryptographically	B-Protocol
Generated	I-Protocol
Addresses	I-Protocol
(	O
CGA	O
)	O
and	O
other	O
new	O
NDP	O
options	O
for	O
the	O
ICMPv6	B-Protocol
packet	O
types	O
used	O
in	O
NDP	O
.	O
</s>
<s>
SEND	O
was	O
updated	O
to	O
use	O
the	O
Resource	B-Protocol
Public	I-Protocol
Key	I-Protocol
Infrastructure	I-Protocol
(	O
RPKI	B-Protocol
)	O
by	O
RFC	O
6494	O
and	O
RFC	O
6495	O
which	O
define	O
use	O
of	O
a	O
SEND	O
Certificate	O
Profile	O
utilizing	O
a	O
modified	O
RFC	O
6487	O
RPKI	B-Protocol
Certificate	O
Profile	O
which	O
must	O
include	O
a	O
single	O
RFC	O
3779	O
IP	O
Address	O
Delegation	O
extension	O
.	O
</s>
<s>
There	O
have	O
been	O
concerns	O
with	O
algorithm	O
agility	O
vis-à-vis	O
attacks	O
on	O
hash	O
functions	O
used	O
by	O
SEND	O
expressed	O
in	O
RFC	O
6273	O
,	O
as	O
CGA	O
currently	O
uses	O
the	O
SHA-1	B-Algorithm
hash	I-Algorithm
algorithm	O
and	O
PKIX	O
certificates	O
and	O
does	O
not	O
provide	O
support	O
for	O
alternative	O
hash	O
algorithms	O
.	O
</s>
