CS8, 10F, H06, due Thu Lecture 10.21—Miller/Ranum 3.4-3.6 (thru p. 93-108).—Total points: ?

Available online as http://www.cs.ucsb.edu/~pconrad/cs8/10F/homework/H06—printable PDF

Name: (4 pts)   Umail Address: (4 pts)   @umail.ucsb.edu
Lab Section (2 pts)—circle one:  9am   10am   11am   noon   unknown   crashing 
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This assignment is due in Lecture on Thursday, 10.21.
It may ONLY be submitted in Lecture, at 2pm on Thursday.

You must come IN PERSON to turn it in during your assigned Lecture section.


Check this link for chapter 3 typos: j.mp/ch3typos-ppic

Read pages 93-108 in Chapter 3—sections 3.4, 3.5, and 3.6. Then answer these questions. You may want to have the code from these pages available—you can find it at the links below.

  1. You may have noticed that parents of small children sometimes spell out words as a means of trying to keep their children from knowing what they are talking about. For example, they might say:

    Remember to pick up some   i-c-e  c-r-e-a-m  for the p-a-r-t-y.

    Or, if you have a dog, you might say: I need to give the d-o-g his weekly b-a-t-h.

    You spell out the words so that the small children or pets don't hear certain words that will cause them to behave in ways that may be annoying to the adults around them.

    Page 93 describes the terms plaintext, ciphertext, encryption and decryption.

    Describe how each of these four words applies to the situation described—that is, in this situation:

    1. ( 5 pts) What is the plaintext?



    2. (5 pts) What is the ciphertext?



    3. (5 pts) What is the encryption?



    4. (5 pts) What is the decryption?




  2. Please turn over for more...

    ...continued from other side

  3. (Note that the book's shows the ciphertext as twsadr_n_tryng + tI_a__akadsom_ih—but that isn't really the final ciphertext. It is indicating that strings "twsadr_n_tryng" and "tI_a__akadsom_ih" should be concatenated together by using the + operator.
    (10 pts) Page 95 describes a process for encrypting
    "It was a dark and stormy night" using the "rail fence cipher", with the result being "twsadr_n_tryngtI_a__akadsom_ih".


    What is the encryption of the phrase "Go Gauchos" in this same cipher?











  4. (10 pts) Here is a secret message encoded with the rail fence cipher. What is the secret message?

    S_sfnC8i_u













End of H06