<s>
Knapsack	B-General_Concept
cryptosystems	I-General_Concept
are	O
cryptosystems	B-General_Concept
whose	O
security	O
is	O
based	O
on	O
the	O
hardness	O
of	O
solving	O
the	O
knapsack	B-Algorithm
problem	I-Algorithm
.	O
</s>
<s>
However	O
,	O
that	O
type	O
of	O
cryptosystem	B-General_Concept
is	O
a	O
good	O
candidate	O
for	O
post-quantum	O
cryptography	O
.	O
</s>
<s>
The	O
most	O
famous	O
knapsack	B-General_Concept
cryptosystem	I-General_Concept
is	O
the	O
Merkle-Hellman	B-Algorithm
Public	I-Algorithm
Key	I-Algorithm
Cryptosystem	I-Algorithm
,	O
one	O
of	O
the	O
first	O
public	B-Application
key	I-Application
cryptosystems	I-Application
,	O
published	O
the	O
same	O
year	O
as	O
the	O
RSA	B-Architecture
cryptosystem	I-Architecture
.	O
</s>
<s>
However	O
,	O
there	O
exist	O
modern	O
knapsack	B-General_Concept
cryptosystems	I-General_Concept
that	O
are	O
considered	O
secure	O
so	O
far	O
:	O
among	O
them	O
is	O
Nasako-Murakami	O
2006	O
.	O
</s>
<s>
Knapsack	B-General_Concept
cryptosystems	I-General_Concept
,	O
when	O
not	O
subject	O
to	O
classical	O
cryptoanalysis	O
,	O
are	O
believed	O
to	O
be	O
difficult	O
even	O
for	O
quantum	O
computers	O
.	O
</s>
<s>
That	O
is	O
not	O
the	O
case	O
for	O
systems	O
that	O
rely	O
on	O
factoring	O
large	O
integers	O
,	O
like	O
RSA	B-Architecture
,	O
or	O
computing	O
discrete	O
logarithms	O
,	O
like	O
ECDSA	O
,	O
problems	O
solved	O
in	O
polynomial	O
time	O
with	O
Shor	B-Algorithm
's	I-Algorithm
algorithm	I-Algorithm
.	O
</s>
