IS Lab 1 - Progress So Far

IS/Lab/Lab1/q2_autokey.py

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+def vigenere_en(ptext, vk):
+    result = ""
+    ptext = ptext.upper()
+    vk = vk.upper()
+
+    kl = len(vk) ## key length
+
+    for i in range(len(ptext)):
+        ch = ptext[i]
+        if 32 <= ord(ch) <= 47:
+            result += ch
+        elif 65 <= ord(ch) <= 90:
+            shift = (ord(vk[i % kl]) - ord('A')) % 26
+            result += chr((ord(ch) - ord('A') + shift) % 26 + ord('A'))
+        else:
+            result += ch
+
+    return result
+
+
+def vigenere_de(ctext, vk):
+    result = ""
+    ctext = ctext.upper()
+    vk = vk.upper()
+
+    kl = len(vk)
+
+    for i in range(len(ctext)):
+        ch = ctext[i]
+        if 32 <= ord(ch) <= 47:
+            result += ch
+        elif 65 <= ord(ch) <= 90:
+            shift = (ord(vk[i % kl]) - ord('A')) % 26
+            result += chr((ord(ch) - ord('A') - shift + 26) % 26 + ord('A'))
+        else:
+            result += ch
+
+    return result
+
+
+def autokey_en(ptext, ak):
+    result = ""
+    ptext = ptext.upper()
+    current_key = ak
+
+    for i in range(len(ptext)):
+        ch = ptext[i]
+        if 32 <= ord(ch) <= 47:
+            result += ch
+        elif 65 <= ord(ch) <= 90:
+            shift = (current_key - ord('A')) % 26
+            cipher_char = chr((ord(ch) - ord('A') + shift) % 26 + ord('A'))
+            result += cipher_char
+            current_key = ord(cipher_char)
+        else:
+            result += ch
+
+    return result
+
+def autokey_de(ctext, ak):
+    result = ""
+    ctext = ctext.upper()
+    current_key = ak
+
+    for i in range(len(ctext)):
+        ch = ctext[i]
+        if 32 <= ord(ch) <= 47:
+            result += ch
+        elif 65 <= ord(ch) <= 90:
+            shift = (current_key - ord('A')) % 26
+            plain_char = chr((ord(ch) - ord('A') - shift + 26) % 26 + ord('A'))
+            result += plain_char
+            current_key = ord(plain_char)
+        else:
+            result += ch
+
+    return result
+
+def operator(argument,ptext,ak,vk):
+    match argument:
+        case '1':
+            print("Vigenere Cipher")
+            print("Plaintext: ", ptext)
+            print("Vigenere Key: ", vk)
+            ctext = vigenere_en(ptext, vk)
+            print("Ciphertext: ", ctext)
+            print("Decrypted Text: ", vigenere_de(ctext, vk))
+        case '2':
+            print("Autokey Cipher")
+            print("Plaintext: ", ptext)
+            print("Auto Key: ", ak)
+            ctext = autokey_en(ptext, ak)
+            print("Ciphertext: ", ctext)
+            print("Decrypted Text: ", autokey_de(ctext, ak))
+        case '3':
+            print("Goodbye")
+            exit()
+        case _:
+            print("Invalid Choice, please try again.")
+
+def main():
+    ptext = input("Kindly enter your desired plaintext: ")
+    vk = input("Kindly enter the Vigenere Key: ")
+    ak = int(input("Kindly enter the Autokey: "))
+
+    print("Welcome to the Autokey cipher system.")
+    print("Enter your choice of algorithm")
+    print("1. Vigenere Cipher")
+    print("2. Autokey Cipher")
+    print("3. Exit")
+
+    while True:
+        op = input("Enter your choice of operation: ")
+        operator(op, ptext, ak, vk)
+
+
+if __name__ == '__main__':
+    main()