1. 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...

1. 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.

2. Consider the polyalphabetic system shown in Figure 8.4. Will a chosenplaintext attack that is able to get the plaintext encoding of the message “The quick brown fox jumps over the lazy dog.” be sufficient to decode all messages? Why or why not?