1) Do the following encryption/decryption problems manually (i.e., without relying on a computer). You need only encrypt the alphabetic characters - leave any punctuation as is.
(a) Encrypt the following Alice in Wonderland quote using ROT-13:
WHY IS A RAVEN LIKE A WRITING DESK?
(b) Decrypt the following message, which was encrypted using rotation-based encryption:
IJ RDNZ ADNC RJPGY BJ VITRCZMZ RDOCJPO V KJMKJDNZ
(c) Decrypt the following message, which was generated with substitution-based encryp-tion:
MU BERZ, NEZE GE MVYW ZVP RY KRYW RY GE ARP IVYW WC YWRU XP THRAE.RPB XK UCV GXYN WC LC RPUGNEZE UCV MVYW ZVP WGXAE RY KRYW RY WNRW.
Let's use another technique to encrypt (a shortened version of) the Alice in Wonderland quote from Problem 1(a):
WHY A RAVEN?
(a) First, change each character, including the spaces and the problem mark, into its decimal ASCII equivalent. prepare all the decimal numbers together from left to right to form a single number.
(b) Take your answer from part (a) and transpose each pair of digits. So, for ex, if your answer in part (a) was 12345678, you'd transpose the 1 and the 2, then the 3 and the 4, then the 5 and the 6, then the 7 and the 8, to get 21436587. (Your actual answer
from part (a) should be longer than the 8-digit ex used here.)
(c) Now move the last digit to the front of the number. Then taking two digits at a time,from left to right, turn each two-digit pair into the corresponding ASCII equivalent. So,for ex, if you have 21436587 from part (b), moving the last digit to the front would
give 72143658. Then 72 is an H, 14 is the non-printing SO (shift out) character, 36 is a dollar sign $, and 58 is a colon : . In writing your final answer, enclose any non-printing characters in parentheses. So the encrypted message would be H(shift out)$:
(d) Is this encryption message a character-by-character substitution cipher? That is, does it always take each occurrence of a character in the plaintext to the same character in the ciphertext? Say 'yes' or 'no' and justify your answer.