I need help to finish my introduction to the science and history of secret writing (cryptography)

Homework 6 (due 2/22 by midnight, end of day)CSC 233
We talked about some early American cryptography and various forms of columnar transposition
ciphers. Next week we’ll see how to break irregular transposition ciphers (with crib).
Handing it in: Submit to the d2l submission folder. Use some standard format for your homework (Word
or pdf, for example). Do not include the questions in your homework documentIf necessary you can
include handwritten answers as pictures, but please make sure the writing is legible (pencils often do
not show up well in pictures). The vast majority of your assignment should be typed. Please include all
work in a single file (don’t use zip). The class information folder contains a sample homework
submission (hwexample.docx or hwexample.pdf). Note how I cropped and resized the image to make it
more readable.
1. (Reading) Read Section 4.1-4.4 (1st edition), or 3.1-3.4 (2nd edition) of the textbook on
transposition ciphers.
2. (An American Friend, 10pt) An American friend of yours, initials JL, sent you the following
message.
I can only say 5, 4, 11, 25, 4, 21, 9, 10, 5.
Hint: Find the right system. It might help to look for clues in this weeks slideshow. Any guesses
for the key? You may want to reread the initial part of this problem.
3. (Simple regular transposition cipher, 13pt)
You know that the following ciphertext was encrypted using a regular columnar transposition
with key-length 5.
HLHLN IPTED OEASP SRCWT EEAEM YSIEO EAGNR
HDOTL NEHOI KHETD NSETP TTIPS IORSE DNRRO
a) [1pt] How many rows does each column consist of?
b) [2pt] Identify the columns in the ciphertext and pick the first three letters in each column.
c) [8pt] Anagram the first three letters of each column so obtain the beginning of the
plaintext.
d) [2pt] Based on the order of the columns you found in c) find the whole plaintext.
4. (Simple regular Transposition Cipher, 17pt)
You suspect the following text to have been the result of a regular transposition cipher.
CHEIU EKEAY IDAOS SEFYT NETNF BLEIH ECOOT
YCFNN YIREM CTTNC ROEON W
a) [2pt] Determine all possible key lengths (based on the fact that it is a regular cipher) in the
range 3 – 12.
b) [5pt] You found out (don’t ask how) that the plaintext contains the word “efficiency”.
Determine which letter sequences would have to occur in the ciphertext for every possible keylength you determined in a. E.g. for key-length 3 (which isn’t possible), the ciperhtext would
have to contain “EIEY”, “FCN”, and “FIC”, but it doesn’t contain any of these.
c) [10pt] Based on the key-length you determined in b) break the transposition cipher through
anagramming. As in problem 3, you may want to determine the order of the column using just
the top two or three rows.