Lab 9: Substitution Cipher

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Task Outline

Due Date: Friday, November 22, 2019
Total Points: 10
Implement a Python program that encrypts a message using the substitution cipher.

In a substitution cipher, we encrypt a message by replacing every letter in a plaintext message with some other letter.
In order to perform this encryption, we make use of a key. In the case of the substitution cipher, the key is a mapping of each of the letters of the alphabet to the letter that it should correspond to, when we encrypt it.
To decrypt the message, the receiver of the message would need to know the key, so that they could reverse the process.
A key, for example, might be the string jtrekyavogdxpsncuizlfbmwhq. This 26-character key means that a(the first letter of the alphabet) should be converted into j(the first letter of the key). Similarly, the letter b(the second letter of the alphabet) should be converted into t(the second letter of the key) and so on.
Therefore, a message like hello would be encrypted as vkxxn, replacing each of the letters according to the mapping as determined by the key.

Description	File Size	File Name
`Python` Source Code for Substitution Cipher	1.7KB	lab09.zip

Contents of lab09.zip:

Lab09SubstitutionCipher/
├── substitutioncipher.py
└── testsubstitutioncipher.py

Write a Python program in the file substitutioncipher.py that encrypts a message using the substitution cipher.
You will write your solution in a function called encrypt(message, key) right below the place where it says: YOUR CODE HERE
When the function call encrypt("hello", "jtrekyavogdxpsncuizlfbmwhq") is executed, the output of the program should be: vkxxn

Run the file testsubstitutioncipher.py to execute the PyUnit test bench. PyUnit indicates a successful test with an OK output, and an unsuccessful test with a FAIL output.

Upload the file substitutioncipher.py to the Web-CAT automated grading platform.