Cryptology - Unofficial St. Mary's College of California Web Site

1.7. EXERCISES 23
12. What is the most common letter in English Second most common
13. What are the nine most common letters in English
14. What are some of the least common letters in English
15. What sorts of hills and valleys does the letter frequency count of a portion
of normal English have
16. How do we use a frequency count to break a Caesar Cipher
17. Are Caesar ciphers secure or not Why
18. When would we use Linquist’s method
19. How does Linquist’s method work Why does it work
1.7 Exercises
1. Encipher the following emperors’ names using a Caesar Cipher with the
given key.
(a) Pompeii, key = D.
(b) Vespasian, key = P.
(c) Caligula, key = H.
(d) Nero, key = T.
2. Encipher the following emperor’s names using a Shift Cipher with the
given key.
(a) Damitian, key = 11.
(b) Trajan, key = 5.
(c) Hadrian, key = 19.
3. Decipher the following names. They have been enciphered using a Caesar
cipher with the given key.
(a) GULWOM UOLYFCOM, key = U.
(b) IRGAJOAY, key = G.
(c) TYESBUJYQD, key = Q.
(d) HFXXNZX, key = F.
4. Decipher the following names. They have been enciphered using a Shift
Cipher with the given key.
(a) RDCHIPCIXCT, key = 15.