<s>
The	B-General_Concept
Amazon	I-General_Concept
Kindle	I-General_Concept
e-book	O
reader	O
DRM	O
system	O
uses	O
the	O
PC1	B-Algorithm
cipher	I-Algorithm
,	O
also	O
called	O
the	B-General_Concept
Kindle	I-General_Concept
cipher	O
or	O
Pukall	O
cipher	O
1	O
.	O
</s>
<s>
The	O
PC1	B-Algorithm
cipher	I-Algorithm
was	O
designed	O
by	O
Alexander	O
Pukall	O
in	O
1991	O
.	O
</s>
