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

4.8. EXERCISES 69
5. Here we work with Decimation Ciphers modulo 28, using 27 = .
(a) Encipher no spaces allowed with key 19.
(b) Decipher CUDAZ KOTQW A. The enciphering key was 17.
(c) Decipher XDOMQM HKE Q JYBQM KT . The enciphering key was 11.
(d) Decipher P WHO ENOWL MKI. The enciphering key was 13.
6. Encipher the following words, using the given linear cipher modulo 26.
(a) Geometry, 3m + 7.
(b) Algebra, 11m + 19.
(c) Trigonometry, 7m + 2.
7. Decipher the following words. They were enciphered with a linear cipher,
modulo 26.
(a) VFQDY DMBMP O, key 5m + 20.
(b) TKIAB CVFQ, key 23m + 4.
(c) YVZGN YNX, key 19m + 8.
(d) HGZGR HGRXH, key 25m + 1.
8. What happens if we follow a linear cipher by another linear cipher
9. In this problem we work as we did in Chapter 3 Exercise 8: the numbers
0 to 9 stand for themselves in the plaintext, 10 is for spaces, 11 to 36
represent the letters of the alphabet, and we work modulo 37.
(a) Encipher 8 or 9 using a Caesar cipher with key 11.
(b) Encipher 25 cents using a Decimation cipher with key 18.
(c) Encipher Tea for 2 using a Linear Cipher with key 13m + 6.
(d) Decipher NAA52 5I5NB 75I52 5NAA. It was enciphered with a Decimation
cipher with key k = 19.
(e) Decipher 9AIB ZE0AD ZAEJB A9D66 PL. It was enciphered with a
Linear Cipher with key 15m + 9.
(f) Decipher REHQD HMHTQ H7. It was enciphered with a Linear Cipher
with key 8m + 12.
(g) Decipher A0L6O ISS. It was enciphered with a Linear Cipher with
key 16m + 7.
(h) Decipher 5UHUE XUKEL U5UH. It was enciphered with a Linear Cipher
with key 31m + 17.
(i) Decipher L2 83 3 T20 JIQ. It was enciphered with a Linear Cipher
with key 13m + 20.