<s>
A	O
cryptoperiod	B-General_Concept
is	O
the	O
time	O
span	O
during	O
which	O
a	O
specific	O
cryptographic	O
key	O
is	O
authorized	O
for	O
use	O
.	O
</s>
<s>
Common	O
government	O
guidelines	O
range	O
from	O
1	O
to	O
3	O
years	O
for	O
asymmetric	B-Application
cryptography	I-Application
,	O
and	O
1	O
day	O
to	O
7	O
days	O
for	O
symmetric	O
cipher	B-Application
traffic	O
keys	O
.	O
</s>
<s>
The	O
code	O
word	O
for	O
a	O
key	O
change	O
,	O
in	O
NSA	O
parlance	O
,	O
is	O
HJ	O
or	O
Hotel	B-General_Concept
Juliet	I-General_Concept
in	O
the	O
NATO	O
phonetic	O
alphabet	O
.	O
</s>
