Question

We have intercepted a message that we need to decode. Luckily, we know that they use the letters A to Z, space, 0 to 9. We also know that when they encode messages they start by shifting the first letter once to the right, then shift the next two letters left twice, then the next three letters right 3 times, then the next four letters left 4 times, the next five letters right 5 times, and so on.

a. If the message intercepted was 8YQDPXN6E what was the original message?

b. What would we get if we encoded the phrase TRENT 20 using the given algorithm?

Answer 1

a.

For decrypting the message, we need to follow the reverse process of encryption, as follows :

• 8
  • each character 1 times to left
  • so we get 7

• YQ
  • each character 2 times to right
  • so we get <space>S
• DPX
  • each character 3 times to left
  • so we get AMU
• N6E
  • each character 4 times to right
  • so we get RAI

Thus, the decrypted message is

7 SAMURAI

b.

For encrypting the message, we proceed as follows :

• T
  • each character 1 times to right
  • so we get U

• RE
  • each character 2 times to left
  • so we get PC
• NT<space>
  • each character 3 times to right
  • so we get QW2
• 20
  • each character 4 times to left
  • so we get ZX

Thus, the encrypted message is

UPCQW2ZX