Cryptography Reference
In-Depth Information
substitution cipher and, second, to aid him in selecting
the likeliest equivalences of letters to be tried.
l
etter
frequenCy
distribution
for
a
samPle
e
nglish
text
number of
occurrences
number of
occurrences
vletter
frequency
letter
frequency
E
8,915
0.127
Y
1,891
0.027
T
6,828
0.097
U
1,684
0.024
I
5,260
0.075
M
1,675
0.024
A
5,161
0.073
F
1,488
0.021
O
4,814
0.068
B
1,173
0.017
N
4,774
0.067
G
1,113
0.016
S
4,700
0.067
W
914
0.013
R
4,517
0.064
V
597
0.008
H
3,452
0.049
K
548
0.008
C
3,188
0.045
X
330
0.005
L
2,810
0.04
Q
132
0.002
D
2,161
0.031
Z
65
0.001
P
2,082
0.03
J
56
0.001
The table shows the approximate number of occur-
rences of each letter in the text of this topic, which in turn
approximates the raw frequency distribution for most
technical material. The following cipher is an encryption
of the first sentence of the previous paragraph (minus the
parenthetical clause) using a monoalphabetic substitution:
UFMDHQAQTMGRG BX GRAZTW PWM
UFMDHBGMGHWOG VWDWAVG BA BAW
GRODTW XQUH AQOWTM HCQH HFQUWG
BX GHFIUHIFW BF DQHHWFA RA HCW
DTQRAHWLH OQM GIFJRJW WAUFMDHRBA
