rel="nofollow" href="#fb3_img_img_679798b2-cb04-5aba-a887-86cc24ed8354.png" alt="1 comma 8 comma 15 comma ellipsis"/>, this will still be the case. Therefore, the most frequent cipher text letter in positions We will first try the case where the period is 4, and we will determine the character frequencies for the {
from which we obtain the following table of frequencies:
| A | B | C | D | E | F | G | H | I | J | K | L | M |
| 1 | 0 | 2 | 3 | 1 | 0 | 6 | 0 | 0 | 1 | 2 | 0 | 1 |
| N | O | P | Q | R | S | T | U | V | W | X | Y | Z |
| 0 | 0 | 5 | 0 | 0 | 0 | 1 | 1 | 4 | 0 | 0 | 0 | 0 |
Since G is the most frequently occurring letter, we make the assumption that “e” enciphers to G. Thus the first key letter might be “C.” Similarly, for the second set of letters (i.e. the
| A | B | C | D | E | F | G | H | I | J | K | L | M |
| 0 | 1 | 0 | 1 | 0 | 5 | 2 | 4 | 2 | 0 | 1 | 0 | 1 |
| N | O | P | Q | R | S | T | U | V | W | X | Y | Z |
| 0 | 1 | 0 | 1 | 0 | 4 | 0 | 1 | 2 | 1 | 0 | 0 | 1 |
Here there are three letters which could likely decipher to “e.” To determine which letter is the right choice, consider each character separately. If “e” enciphers to “F,” we have a key letter of “B.” If “e” enciphers to “H,” we have a key letter of “D.” Finally, if “e” enciphers to “S,” we have a key letter of “O.” Now, we must examine each choice case by case. A key letter of “B” means that the most frequently occurring letters besides “e” are “g” and “r.” Similarly, a key letter of “D” means that the most frequently occurring letters in the plain text (in positions
For the
| A | B | C | D | E | F | G | H |
|
