<s>
In	O
symmetric	B-Algorithm
key	I-Algorithm
cryptography	I-Algorithm
,	O
both	O
parties	O
must	O
possess	O
a	O
secret	O
key	O
which	O
they	O
must	O
exchange	O
prior	O
to	O
using	O
any	O
encryption	O
.	O
</s>
<s>
In	O
public	B-Application
key	I-Application
cryptography	I-Application
,	O
the	O
key	B-General_Concept
distribution	I-General_Concept
of	O
public	B-Application
keys	I-Application
is	O
done	O
through	O
public	B-Application
key	I-Application
servers	O
.	O
</s>
<s>
When	O
a	O
person	O
creates	O
a	O
key-pair	O
,	O
they	O
keep	O
one	O
key	O
private	O
and	O
the	O
other	O
,	O
known	O
as	O
the	O
public-key	B-Application
,	O
is	O
uploaded	O
to	O
a	O
server	O
where	O
it	O
can	O
be	O
accessed	O
by	O
anyone	O
to	O
send	O
the	O
user	O
a	O
private	O
,	O
encrypted	O
,	O
message	O
.	O
</s>
<s>
Secure	B-Protocol
Sockets	I-Protocol
Layer	I-Protocol
(	O
SSL	O
)	O
uses	O
Diffie	B-Protocol
–	I-Protocol
Hellman	I-Protocol
key	I-Protocol
exchange	I-Protocol
if	O
the	O
client	O
does	O
not	O
have	O
a	O
public-private	O
key	O
pair	O
and	O
a	O
published	O
certificate	O
in	O
the	O
public	B-Architecture
key	I-Architecture
infrastructure	I-Architecture
,	O
and	O
Public	B-Application
Key	I-Application
Cryptography	I-Application
if	O
the	O
user	O
does	O
have	O
both	O
the	O
keys	O
and	O
the	O
credential	O
.	O
</s>
<s>
Key	B-General_Concept
distribution	I-General_Concept
is	O
an	O
important	O
issue	O
in	O
wireless	O
sensor	O
network	O
(	O
WSN	O
)	O
design	O
.	O
</s>
<s>
There	O
are	O
many	O
key	B-General_Concept
distribution	I-General_Concept
schemes	O
in	O
the	O
literature	O
that	O
are	O
designed	O
to	O
maintain	O
an	O
easy	O
and	O
at	O
the	O
same	O
time	O
secure	O
communication	O
among	O
sensor	O
nodes	O
.	O
</s>
<s>
The	O
most	O
accepted	O
method	O
of	O
key	B-General_Concept
distribution	I-General_Concept
in	O
WSNs	O
is	O
key	O
predistribution	O
,	O
where	O
secret	O
keys	O
are	O
placed	O
in	O
sensor	O
nodes	O
before	O
deployment	O
.	O
</s>
<s>
For	O
more	O
info	O
see	O
:	O
key	B-Device
distribution	I-Device
in	I-Device
wireless	I-Device
sensor	I-Device
networks	I-Device
.	O
</s>
<s>
Key	B-General_Concept
distribution	I-General_Concept
and	O
key	O
storage	O
are	O
more	O
problematic	O
in	O
the	O
cloud	O
due	O
to	O
the	O
transitory	O
nature	O
of	O
the	O
agents	O
on	O
it	O
.	O
</s>
<s>
Secret	B-Architecture
sharing	I-Architecture
can	O
be	O
used	O
to	O
store	O
keys	O
at	O
many	O
different	O
servers	O
on	O
the	O
cloud	O
.	O
</s>
<s>
In	O
secret	B-Architecture
sharing	I-Architecture
,	O
a	O
secret	O
is	O
used	O
as	O
a	O
seed	O
to	O
generate	O
a	O
number	O
of	O
distinct	O
secrets	O
,	O
and	O
the	O
pieces	O
are	O
distributed	O
so	O
that	O
some	O
subset	O
of	O
the	O
recipients	O
can	O
jointly	O
authenticate	O
themselves	O
and	O
use	O
the	O
secret	O
information	O
without	O
learning	O
what	O
it	O
is	O
.	O
</s>
<s>
Secret	B-Architecture
sharing	I-Architecture
is	O
used	O
in	O
cases	O
where	O
one	O
wishes	O
to	O
distribute	O
a	O
secret	O
among	O
N	O
shares	O
so	O
that	O
M	O
<	O
N	O
of	O
them	O
(	O
M	O
of	O
N	O
)	O
can	O
regenerate	O
the	O
original	O
secret	O
,	O
but	O
no	O
smaller	O
group	O
up	O
to	O
M	O
1	O
can	O
do	O
so	O
.	O
</s>
