Using the monoalphabetic cipher in Figure 8.3, encode the message “This is a secret message.” Decode the message “fsgg ash.” Show that Trudy’s known-plaintext attack, in which she knows the...

Using the monoalphabetic cipher in Figure 8.3, encode the message “This is

a secret message.” Decode the message “fsgg ash.”

Show that Trudy’s known-plaintext attack, in which she knows the (ciphertext, plaintext) translation pairs for seven letters, reduces the number of

possible substitutions to be checked in the example in Section 8.2.1 by

approximately 109.