cil-academy-python-challenge's Introduction

CIL-Academy-Python-Challenge

Cryptography Challenge

Cryptography, or cryptology is the practice and study of techniques for secure communication. Cryptography relies on using more or less complex encryption algorithms to encode a readable message (plaintext) into a collection of characters (ciphertext) that is hard to decipher (decode).

The Python Code

#Cryptography Challenge #1
import random, time
#A basic encryption algorithm...
def encrypt(plaintext, key):
  alphabet = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
  ciphertext = ""
  for i in range(0,len(plaintext)):
    character = plaintext[i]
    ciphertext = ciphertext + character
    for j in range (0,key):
      ciphertext = ciphertext + random.choice(alphabet)
  return ciphertext
#Main program starts here...
#Input...
plaintext = input("Enter a message to encrypt (plaintext)")
key = int(input("Input a key as a number between 1 and 10"))
while not (key>=1 and key<=10):
  print("Invalid key, try again!")
  key = int(input("Input a key as a number between 1 and 10"))

#Process... 
print("...")
time.sleep(1)
print("Encrypting plaintext...")
time.sleep(1)
print("...")
time.sleep(1)
ciphertext = encrypt(plaintext, key)
#Output...
print("Ciphertext:")
print(ciphertext)

The Challenge

Your first task is to reverse-engineer this code to understand how this encryption algorithm works. Then, your challenge consists of writing a new function called decrypt(), that takes two parameters (a ciphertext and a key) and returns the plaintext corresponding to the given ciphertext. Update the table below with the answers obtained from your decrypt() function

Decryption Table

Using your new decrypt() function, decrypt the following messages:

Example Run

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