IS Lab 1 - Progress So Far

IS/Lab/Lab1/q1_monosub.py

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+## ptext = plaintext
+## ak = additive key
+from collections import defaultdict
+
+def add_cipher_en(ptext, ak):
+    result = ""
+    for i in range(len(ptext)):
+        ch = ptext[i]
+        if 32 <= ord(ch) <= 47:
+            result += ch
+        elif 90 >= ord(ch) >= 65:
+            result += chr((ord(ch) + ak - 65) % 26 + 65)
+        else:
+            result += chr((ord(ch) + ak - 97) % 26 + 97)
+    return result
+
+def add_cipher_de(ctext, ak):
+    result = ""
+    for i in range(len(ctext)):
+        ch = ctext[i]
+        if 32 <= ord(ch) <= 47:
+            result += ch
+        elif 90 >= ord(ch) >= 65:
+            result += chr((ord(ch) - ak - 65) % 26 + 65)
+        else:
+            result += chr((ord(ch) - ak - 97) % 26 + 97)
+    return result
+
+def mult_cipher_en(ptext, mk):
+    result = ""
+    for i in range(len(ptext)):
+        ch = ptext[i]
+        if 32 <= ord(ch) <= 47:
+            result += ch
+        elif 90 >= ord(ch) >= 65:
+            result += chr((ord(ch) * mk - 65) % 26 + 65)
+        else:
+            result += chr((ord(ch) * mk - 97) % 26 + 97)
+    return result
+
+def mult_cipher_de(ctext, mk):
+    result = ""
+    inverse = pow(mk, -1, 26)
+    for i in range(len(ctext)):
+        ch = ctext[i]
+        if 32 <= ord(ch) <= 47:
+            result += ch
+        elif 90 >= ord(ch) >= 65:
+            result += chr((ord(ch) * inverse - 65) % 26 + 65)
+        else:
+            result += chr((ord(ch) * inverse - 97) % 26 + 97)
+    return result
+
+def affine_en(ptext, ak, mk):
+    result = ""
+    for i in range(len(ptext)):
+        ch = ptext[i]
+        if 32 <= ord(ch) <= 47:
+            result += ch
+        elif 90 >= ord(ch) >= 65:
+            result += chr((((ord(ch) - 65) * mk) + ak) % 26 + 65)
+        else:
+            result += chr((((ord(ch) - 97) * mk) + ak) % 26 + 97)
+    return result
+
+def affine_de(ctext, ak, mk):
+    result = ""
+    inverse = pow(mk, -1, 26)
+    for i in range(len(ctext)):
+        ch = ctext[i]
+        if 32 <= ord(ch) <= 47:
+            result += ch
+        elif 90 >= ord(ch) >= 65:
+            result += chr((((ord(ch) - 65 - ak) * inverse) % 26) + 65)
+        else:
+            result += chr((((ord(ch) - 97 - ak) * inverse) % 26) + 97)
+    return result
+
+def operator(argument,ptext,ak,mk):
+    match argument:
+        case '1':
+            print("Additive Cipher")
+            print("Plaintext: ", ptext)
+            print("Additive Key: ", ak)
+            ctext = add_cipher_en(ptext, ak)
+            print("Ciphertext: ", ctext)
+            print("Decrypted Text: ", add_cipher_de(ctext, ak))
+        case '2':
+            print("Multiplicative Cipher")
+            print("Plaintext: ", ptext)
+            print("Multiplicative Key: ", mk)
+            ctext = mult_cipher_en(ptext, mk)
+            print("Ciphertext: ", ctext)
+            print("Decrypted Text: ", mult_cipher_de(ctext, mk))
+        case '3':
+            print("Affine Cipher")
+            print("Plaintext: ", ptext)
+            print("Additive Key: ", ak)
+            print("Multiplicative Key: ", mk)
+            ctext = affine_en(ptext, ak, mk)
+            print("Ciphertext: ", ctext)
+            print("Decrypted Text: ", affine_de(ctext, ak, mk))
+        case '4':
+            print("Goodbye")
+            exit()
+        case _:
+            print("Invalid Choice, please try again.")
+
+def main():
+    ptext = input("Kindly enter your desired plaintext: ")
+    ak = 20
+    mk = 15
+
+    print("Welcome to the substitution cipher system.")
+    print("Enter your choice of algorithm")
+    print("1. Additive Cipher")
+    print("2. Multiplicative Cipher")
+    print("3. Affine Cipher")
+    print("4. Exit")
+
+    while True:
+        op = input("Enter your choice of operation: ")
+        operator(op, ptext, ak, mk)
+
+
+if __name__ == '__main__':
+    main()