<s>
In	O
cryptography	O
,	O
a	O
cryptosystem	B-General_Concept
is	O
a	O
suite	O
of	O
cryptographic	O
algorithms	O
needed	O
to	O
implement	O
a	O
particular	O
security	O
service	O
,	O
such	O
as	O
confidentiality	O
(	O
encryption	O
)	O
.	O
</s>
<s>
Typically	O
,	O
a	O
cryptosystem	B-General_Concept
consists	O
of	O
three	O
algorithms	O
:	O
one	O
for	O
key	O
generation	O
,	O
one	O
for	O
encryption	O
,	O
and	O
one	O
for	O
decryption	O
.	O
</s>
<s>
The	O
term	O
cipher	B-Application
(	O
sometimes	O
cypher	O
)	O
is	O
often	O
used	O
to	O
refer	O
to	O
a	O
pair	O
of	O
algorithms	O
,	O
one	O
for	O
encryption	O
and	O
one	O
for	O
decryption	O
.	O
</s>
<s>
Therefore	O
,	O
the	O
term	O
cryptosystem	B-General_Concept
is	O
most	O
often	O
used	O
when	O
the	O
key	O
generation	O
algorithm	O
is	O
important	O
.	O
</s>
<s>
For	O
this	O
reason	O
,	O
the	O
term	O
cryptosystem	B-General_Concept
is	O
commonly	O
used	O
to	O
refer	O
to	O
public	B-Application
key	I-Application
techniques	O
;	O
however	O
both	O
"	O
cipher	B-Application
"	O
and	O
"	O
cryptosystem	B-General_Concept
"	O
are	O
used	O
for	O
symmetric	B-Algorithm
key	I-Algorithm
techniques	O
.	O
</s>
<s>
Mathematically	O
,	O
a	O
cryptosystem	B-General_Concept
or	O
encryption	O
scheme	O
can	O
be	O
defined	O
as	O
a	O
tuple	B-Application
with	O
the	O
following	O
properties	O
.	O
</s>
<s>
Note	O
;	O
typically	O
this	O
definition	O
is	O
modified	O
in	O
order	O
to	O
distinguish	O
an	O
encryption	O
scheme	O
as	O
being	O
either	O
a	O
symmetric-key	B-Algorithm
or	O
public-key	B-Application
type	O
of	O
cryptosystem	B-General_Concept
.	O
</s>
<s>
A	O
classical	O
example	O
of	O
a	O
cryptosystem	B-General_Concept
is	O
the	O
Caesar	O
cipher	B-Application
.	O
</s>
<s>
A	O
more	O
contemporary	O
example	O
is	O
the	O
RSA	B-Architecture
cryptosystem	I-Architecture
.	O
</s>
