How To Encode And Decode A Message using Python? - GeeksforGeeks

01 Oct, 2020
Encryption is the process of converting a normal message (plain text) into a meaningless message (Ciphertext). Whereas, Decryption is the process of converting a meaningless message (Cipher text) into its original form (Plain text). In this article, we will take forward the idea of encryption and decryption and draft a python program.
In this article, we will be given a single-line message as input it is either encoded or decoded as per requirement and the resultant message is printed as output. Here, the conversion has been done by replacing A to Z, B to Y, ... Z to A. The case of the characters, numbers, spaces, and special characters present in the message is being kept unchanged.
Sample Example 1:
Encryption
Input : Hello World
Output : Svool Dliow

Explanation: (Reference- conversion table)
H is replaced with S
e is replaced with v
l is replaced with o
W is replaced with D
r is replaced with i
Decryption
Input : Svool Dliow 
Output : Hello World 

Explanation: (Reference- conversion table)
S is replaced with H
v is replaced with e
o is replaced with l
D is replaced with W
i is replaced with r
Sample Example 2:
Encryption
Input : GeeksForGeeks
Output : TvvphUliTvvph

Explanation: (Reference- conversion table)
G is replaced with T
e is replaced with v
k is replaced with p
s is replaced with h
F is replaced with U
o is replaced with l
r is replaced with i
Decryption
Input : TvvphUliTvvph 
Output : GeeksForGeeks

Explanation: (Reference- conversion table)
T is replaced with G
v is replaced with e
p is replaced with k
h is replaced with s
U is replaced with F
l is replaced with o
i is replaced with r
Below is the implementation.
Python3
# Taking input from userdata = 'Welcome to GeeksForGeeks...'    # conversion Chartconversion_code = {        # Uppercase Alphabets    'A': 'Z', 'B': 'Y', 'C': 'X', 'D': 'W', 'E': 'V', 'F': 'U',    'G': 'T', 'H': 'S', 'I': 'R', 'J': 'Q', 'K': 'P', 'L': 'O',    'M': 'N', 'N': 'M', 'O': 'L', 'P': 'K', 'Q': 'J', 'R': 'I',    'S': 'H', 'T': 'G', 'U': 'F', 'V': 'E', 'W': 'D', 'X': 'C',    'Y': 'B', 'Z': 'A',      # Lowercase Alphabets    'a': 'z', 'b': 'y', 'c': 'x', 'd': 'w', 'e': 'v', 'f': 'u',    'g': 't', 'h': 's', 'i': 'r', 'j': 'q', 'k': 'p', 'l': 'o',    'm': 'n', 'n': 'm', 'o': 'l', 'p': 'k', 'q': 'j', 'r': 'i',    's': 'h', 't': 'g', 'u': 'F', 'v': 'e', 'w': 'd', 'x': 'c',    'y': 'b', 'z': 'a'}  # Creating converted outputconverted_data = ""    for i in range(0, len(data)):    if data[i] in conversion_code.keys():        converted_data += conversion_code[data[i]]    else:        converted_data += data[i]  # Printing converted outputprint(converted_data)
Dvoxlnv gl TvvphUliTvvph...

cryptography
Python
cryptography
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