This section focuses on cryptography, like we’ve been talking about recently in class. You’ll be encrypting and decrypting messages using multiple cipher algorithms. Remember - Computers typically use more complex ciphers for encrypting and decrypting messages than the ones you’ll do in this section. However, the methods that computers use are hard to do by-hand, so we start simple :). (Note: there are tools online that can help you solve these problems with ease, but you are not allowed to use them!)
(A)
Encrypt the following plaintext using the Caesar cipher technique, with a 3 letter offset:
“I AM GOING TO MAKE HIM AN OFFER HE CANNOT REFUSE”
(B)
Encrypt the following plaintext using the Caesar cipher technique, with a 5 letter offset:
“I FIND YOUR LACK OF FAITH DISTURBING”
(A)
Decrypt the following ciphertext using the caesar cipher technique, with a 2 letter offset:
“K JCXG C HGGNKPI YG CTG PQV KP MCPUCU CPAOQTG”.
(B)
Decrypt the following ciphertext using the Caesar cipher technique, with a 7 letter offset:
“AOLF THF AHRL VBY SPCLZ IBA AOLF DPSS ULCLY AHRL VBY MYLLKVT”
In this problem, you will encrypt and decrypt messages using a substitution cipher that users the following substitution table: Notice that some plain-text letters can encrypt to more than one ciphertext letter. Keep this in mind when doing the translations. You can use the large void of empty space on the right of the table to do the problems.
| Plain | Ciph |
|---|---|
| A | Z M |
| B | 0 |
| C | Y L |
| D | 1 |
| E | X K |
| F | 2 |
| G | W J |
| H | 3 |
| I | V I |
| J | 4 |
| K | U H |
| L | 5 |
| M | T G |
| N | 6 |
| O | S F |
| P | 7 |
| Q | R E |
| R | 8 |
| S | Q |
| T | 9 D |
| U | P |
| V | @ C |
| W | O |
| X | # B |
| Y | N |
| Z | $ A |
(A) Encrypt the following plaintext using the substitution table above: “NEVER TELL ME THE ODDS”
(B) Decrypt the following ciphertext using the substitution table above: “TI61 D8VYUQ 1F 6S9 OF8H F6 TX”
Recall the rail-fence cipher discussed in class. If you need a refresher, review the lecture slides or see the wikipedia article.
(A)
Use a 3-rail rail cipher to encrypt the following text: “FEAR IS THE PATH TO THE DARK SIDE”
(B)
Use a 3-rail rail cipher to decrypt the following text: “UZDNUZEPL”
By the time you are reading this section, we may or many not have discussed the four-square cipher in class. If we have not yet, read the instructions on this site before completing this problem (you might want to regardless, for extra clarification).
practicalcryptography.com/ciphers/mechanical-era/lorenz/
Once you have a grasp on it, go ahead and work on the below problems. For all problems, use the following foursquare for the encryptions and decryptions: Remember, you need to remove spaces before encrypting, and you must figure out where the spaces below manually after decrypting.
a b c d e Z G P T F
f g h i k O I H M U
l m n o p W D R C N
q r s t u Y K E Q A
v w x y z X V S B L
M F N B D a b c d e
C R H S A f g h i k
X Y O G V l m n o p
I T U E W q r s t u
L Q Z K P v w x y z
(A) Encrypt the following message: “ONE RING TO RULE THEM ALL”.
You can remove spaces before encrypting.
(B)
Decrypt the following message that was encrypted with the foursquare shown above: “MYDSNMME”