Cryptography Reference
In-Depth Information
..#
\
.Z+...._..3l
0650
02 e1 23 5c 04 5a 2b 08
0b df 93 5f a3 1a 33 6c
0660
12 71 14 14 16 1a 18 59
5b 5f 5d 5d 5f 63 61 61
.q.....Y[_]]_caa
0670
63 67 65 65 67 6b 69 69
6b 6f 6d 6d 6f 73 71 71
cgeegkiikommosqq
0680
73 77 75 75 77 7b 79 79
7b 7f 7d 7d 7f 83 81 81
swuuw{yy{.}}....
0690
83 87 85 85 87 8b 89 89
8b 8f 8d c6 8f 93 91 91
................
06a0
93 97 95 95 97 9b 99 99
9b 9f 9d 9d 9f a3 a1 a1
................
We can see that, from address 66
a
onwards, every other character forms an
accordingly ascending row, but this time with difference 2:
5b 5d 5f 61 63 65 ...
Perhaps all that's done here is a simple Vigenere cipher and XORing, like
in Section 2.4.2, and then additionally superimposing an ascending number
sequence on everything? One can find out pretty quickly that this is actually
the case. More specifically, the method in WordPerfect 5.1 looks like this:
•
Write bytes with the following numerical values on one row: the first
value is larger than the password length by 1; every following value is
larger than its predecessor by 1; 0 comes after 255.
•
Write the password underneath several times, and
•
underneath it, write the bytes of the WordPerfect file again, starting with
byte number 16.
•
XOR three superimposed characters bitwise. The result is the 'ciphertext'
(Figure 3.9).
Let the password be UNIX, i.e., let it have length 4. The WordPerfect file should
look like this from byte 16 onwards, for example (doesn't happen in practice):
Canon BJ-200 (LQ Mode)
The encrypted text is produced by bitwise XORing the following three rows:
567891011121314151617181920212223242526
UNIXUNIXUNIXUNIXUNIXUN
Canon BJ 200 (LQ Mode)
Figure 3.9:
The encryption method of WordPerfect 5.1.
