Information Security Fundamentals, 2nd Edition

26  ◾  Information Security Fundamentals

a three-character shift. Depending on how large the shift, either by subtraction or

addition, the alphabet will be offset by that much. For instance, a three-character

addition shift would look like Figure 3.1. is shift would change the plaintext

“purple” into the ciphertext “MROMIB.”

If the shift was a three-character subtraction, it would look like Figure 3.2. e

plaintext message “purple” would then become ciphertext “SXUSOH.”

e Atbash cipher flips the entire alphabet back on itself; the plaintext alphabet

is “A–Z” and the ciphertext alphabet is “Z–A,” shown below in Figure 3.3. e

Atbash cipher would ...