EXAMPLE 13 Decimation Cipher
To illustrate the decimation cipher, let’s encrypt the message ATTACK AT DAWN using the key 3.
| Message | A | T | T | A | C | K | A | T | D | A | W | N |
| Position | 0 | 19 | 19 | 0 | 2 | 10 | 0 | 19 | 3 | 0 | 22 | 13 |
| Position × 3 | 0 | 57 | 57 | 0 | 6 | 30 | 0 | 57 | 9 | 0 | 66 | 39 |
| New position | 0 | 5 | 5 | 0 | 6 | 4 | 0 | 5 | 9 | 0 | 14 | 13 |
| Encrypted message | A | F | F | A | G | E | A | F | J | A | O | N |