Add text encryption script

Author: Harshit28j

text_encryption/encryption_method.py

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+import string
+import sys
+
+# Caesar cipher encryption
+def caesar_cipher_encrypt(text, shift):
+    encrypted_text = ""
+    for char in text:
+        if char.isalpha():
+            alphabet = string.ascii_uppercase if char.isupper() else string.ascii_lowercase
+            encrypted_char = alphabet[(alphabet.index(char) + shift) % len(alphabet)]
+            encrypted_text += encrypted_char
+        else:
+            encrypted_text += char
+    return encrypted_text
+
+# Affine cipher encryption
+def affine_cipher_encrypt(text, a, b):
+    encrypted_text = ""
+    for char in text:
+        if char.isalpha():
+            alphabet = string.ascii_uppercase if char.isupper() else string.ascii_lowercase
+            encrypted_char = alphabet[(a * alphabet.index(char) + b) % len(alphabet)]
+            encrypted_text += encrypted_char
+        else:
+            encrypted_text += char
+    return encrypted_text
+
+# Substitution cipher encryption
+def substitution_cipher_encrypt(text, key):
+    encrypted_text = ""
+    for char in text:
+        if char.isalpha():
+            alphabet = string.ascii_uppercase if char.isupper() else string.ascii_lowercase
+            substitution_alphabet = str.maketrans(alphabet, key.upper()) if char.isupper() else str.maketrans(alphabet, key.lower())
+            encrypted_char = char.translate(substitution_alphabet)
+            encrypted_text += encrypted_char
+        else:
+            encrypted_text += char
+    return encrypted_text
+
+# Transposition cipher encryption
+def transposition_cipher_encrypt(text, key):
+    ciphertext = [''] * int(key)
+    for column in range(int(key)):
+        currentIndex = column
+        while currentIndex < len(text):
+            ciphertext[column] += text[currentIndex]
+            currentIndex += int(key)
+
+    return ''.join(ciphertext)
+
+def main():
+    text = input("Enter the text to encrypt: ")
+
+    # Ask user for the encryption method
+    print("Choose an encryption method:")
+    print("1. Caesar cipher")
+    print("2. Affine cipher")
+    print("3. Substitution cipher")
+    print("4. Transposition cipher")
+
+    try:
+        choice = int(input("Enter your choice (1-4): "))
+    except ValueError: #to handle wrong values
+        print("Invlaid selection")
+        sys.exit(0)
+
+    if choice == 1:
+
+        try:
+            shift = int(input("Enter the shift value for Caesar cipher: "))
+            encrypted_text = caesar_cipher_encrypt(text, shift)
+            print("Caesar cipher (encryption):", encrypted_text)
+        except ValueError:
+            print("Invalid Input")
+
+    elif choice == 2:
+
+        try:
+            a = int(input("Enter the value for 'a' in Affine cipher: "))
+            b = int(input("Enter the value for 'b' in Affine cipher: "))
+            encrypted_text = affine_cipher_encrypt(text, a, b)
+            print("Affine cipher (encryption):", encrypted_text)
+
+        except ValueError:
+            print("Invalid Input")
+   
+    elif choice == 3:
+
+        key = input("Enter the substitution key: ")
+        if len(key)==26:
+            encrypted_text = substitution_cipher_encrypt(text, key)
+            print("Substitution cipher (encryption):", encrypted_text)
+        else:
+            print("Key must have the same length as the number of characters in the alphabet (26).")
+
+    elif choice == 4:
+
+        try:
+            transpose_key = input("Enter the transposition key (make sure its less than length of stirng): ")
+            if int(transpose_key)>len(text):
+                print("Key must be less than length of string")
+            else:
+                encrypted_text = transposition_cipher_encrypt(text, transpose_key)
+                print("Transposition cipher (encryption):", encrypted_text)
+                
+        except ValueError:
+            print("Invalid Input")
+
+    else:
+        print("Invalid choice. Please choose a number between 1 and 4.")
+
+if __name__ == "__main__":
+    main()

text_encryption/readme.md

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+# Encryption Script
+
+This script allows you to encrypt text using various encryption methods.
+
+## Installation
+
+1. Make sure you have Python installed on your system.
+2. Clone this repository or download the script file.
+
+## Usage
+
+1. Open a terminal or command prompt.
+2. Navigate to the directory where the script is located.
+3. Run the following command: python script.py
+
+Follow the prompts to enter the text and choose an encryption method.
+Encryption Methods
+
+Caesar Cipher
+The Caesar cipher is a substitution cipher where each letter in the plaintext is shifted a certain number of positions down the alphabet.
+To choose the Caesar cipher, enter 1 when prompted.
+
+Affine Cipher
+The Affine cipher is a substitution cipher that combines the Caesar cipher with multiplication and addition.
+To choose the Affine cipher, enter 2 when prompted.
+
+Substitution Cipher
+The Substitution cipher is a method of encryption where each letter in the plaintext is replaced by another letter according to a fixed key.
+To choose the Substitution cipher, enter 3 when prompted. Note that the key must have the same length as the number of characters in the alphabet (26).
+
+Transposition Cipher
+The Transposition cipher is a method of encryption that rearranges the letters of the plaintext to form the ciphertext.
+To choose the Transposition cipher, enter 4 when prompted. You will also be asked to enter a transposition key, which should be less than the length of the text.
+Note: If you enter an invalid choice or provide incorrect input, appropriate error messages will be displayed.
+
+Example
+Here is an example of running the script:
+Enter the text to encrypt: Hello, World!
+Choose an encryption method:
+1. Caesar cipher
+2. Affine cipher
+3. Substitution cipher
+4. Transposition cipher
+Enter your choice (1-4): 3
+Enter the substitution key: QWERTYUIOPASDFGHJKLZXCVBNM
+Substitution cipher (encryption): ITSSG, KTSSG!