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Activity 4: Encrypt & Decrypt
Introduction to Information Security

In this practical activity, you will encrypt plaintext and decrypt ciphertext using classical ciphers.

50min Easy

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Important! It is illegal to perform any type of intrusion or hacking activities without explicit permission.
Significance: Being able to perform encryption and decryption provides hands-on experience for students to understand the basic concepts of cryptography and ciphers and allows them to develop problem-solving skills and critical thinking .
Prerequisites: Cryptography Module
Requirements: None
Files: None
Related Videos: None
Task #1: Caesar Cipher
By completing this task, you must use your problem solving skills and be able to encrypt and decrypt using the Caesar classical cipher.
Expert & Regular Mode
  1. Encrypt the following plaintext message using key = 4: YOU WILL NEVER CATCH ME
  2. Encrypt the following plaintext message using key = 7: LIBRARY ARTS SECTION
  3. Encrypt the following plaintext message using key = 8: THE BIRD HAS ESCAPED
  4. Decrypt the following ciphertext message using key = 3: FJCLQ VN RO HXD LJW
  5. Decrypt the following ciphertext message using key = 2: VQPKIJV YCTGJQWUG
  6. Decrypt the following ciphertext message using key = 1: FBTZ POF
Solution
Show solution »
  1. CSY AMPP RIZIV GEXGL QI
  2. SPIYHYF HYAZ ZLJAPVU
  3. BPM JQZL PIA MAKIXML
  4. CATCH ME IF YOU CAN
  5. TONIGHT WAREHOUSE
  6. EASY ONE
By completing this task, you must use your problem solving skills and be able to encrypt and decrypt using the Rail Fence classical cipher.
When using the rail fence cipher, the plaintext is written diagonally downwards on successive "rails" of an imaginary fence, then moving up when the bottom rail is reached. When the top rail is reached, the message is written downwards again until the whole plaintext is written out.
Expert & Regular Mode
  1. Encrypt the following plaintext message using key = 2: YOU WILL NEVER CATCH ME
  2. Encrypt the following plaintext message using key = 3: LIBRARY ARTS SECTION
  3. Encrypt the following plaintext message using key = 4: THE BIRD HAS ESCAPED
  4. Decrypt the following ciphertext message using key = 2: RNO UNW
  5. Decrypt the following ciphertext message using key = 3: BNEEID HBX HTO
  6. Decrypt the following ciphertext message using key = 4: WHAN OI AUTR
Solution
Show solution »
  1. YUI LEEC THEOW LNVRA CM
  2. LAREOIR RATS CINBYST
  3. TDC HRHS AEI AEPDBSE
  4. RUN NOW
  5. BEHIND THE BOX
  6. WAIT AN HOUR
Name
Red fields are required.
Caesar
Rail Fence
Vigenere
Caesar
Rail Fence
Vigenere
K
L
Cannot determine without a key
A
Y
Cannot determine
2, 3
9, 3
2, 9

               
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Introduction to Information Security