added lab2 questions

IS/Lab/Lab2/3des.py

@@ -0,0 +1,31 @@
+from Crypto.Cipher import DES3
+from Crypto.Util.Padding import pad, unpad
+
+def des3_cipher(key):
+    return DES3.new(key.encode('utf-8'), DES3.MODE_ECB)
+
+def des3_en(ptext, key):
+    cipher = des3_cipher(key)
+    padded_text = pad(ptext.encode('utf-8'), DES3.block_size)
+    return cipher.encrypt(padded_text)
+
+def des3_de(ctext, key):
+    cipher = des3_cipher(key)
+    decrypted = unpad(cipher.decrypt(ctext), DES3.block_size)
+    return decrypted.decode('utf-8')
+
+def despad_key(key):
+    key = key.ljust(24)[:24]
+    return key
+
+def main():
+    print("Welcome to 3DES (Triple DES)")
+    ptext = input("Enter plaintext: ")
+    key = input("Enter key (minimum 16 characters for 3DES): ")
+    key = despad_key(key)
+    ctext = des3_en(ptext, key)
+    print("Your ciphertext: ", ctext)
+    print("Your decrypted plaintext: ", des3_de(ctext, key))
+
+if __name__ == '__main__':
+    main()

IS/Lab/Lab2/aes_128.py

@@ -0,0 +1,34 @@
+from Crypto.Cipher import AES
+from Crypto.Util.Padding import pad, unpad
+
+def aes_cipher(key):
+    return AES.new(key.encode('utf-8'), AES.MODE_ECB)
+
+def aes_en(ptext, key):
+    cipher = aes_cipher(key)
+    ptext = pad(ptext.encode('utf-8'), AES.block_size)
+    return cipher.encrypt(ptext)
+
+def aes_de(ctext, key):
+    cipher = aes_cipher(key)
+    decrypted = cipher.decrypt(ctext)
+    return unpad(decrypted, AES.block_size).decode('utf-8')
+
+def aespad_key(key):
+    return key.ljust(16)[:16]
+
+    # 16 for 128 bit, 24 for 192, 32 for 256
+
+def main():
+    print("Welcome to AES-128")
+    ptext = input("Enter plaintext: ")
+    key = input("Enter key: ")
+
+    key = aespad_key(key)
+
+    ctext = aes_en(ptext, key)
+    print("Your ciphertext: ", ctext)
+    print("Your decrypted plaintext: ", aes_de(ctext, key))
+
+if __name__ == '__main__':
+    main()

IS/Lab/Lab2/aes_192.py

@@ -0,0 +1,29 @@
+from Crypto.Cipher import AES
+from Crypto.Util.Padding import pad, unpad
+
+def aes_cipher(key):
+    return AES.new(key.encode('utf-8'), AES.MODE_ECB)
+
+def aes_en(ptext, key):
+    cipher = aes_cipher(key)
+    ptext = pad(ptext.encode('utf-8'), AES.block_size)
+    return cipher.encrypt(ptext)
+
+def aes_de(ctext, key):
+    cipher = aes_cipher(key)
+    decrypted = cipher.decrypt(ctext)
+    return unpad(decrypted, AES.block_size).decode('utf-8')
+
+def aespad_key(key):
+        return key.ljust(24)[:24]
+
+def main():
+    ptext = input("Enter plaintext: ")
+    key = input("Enter key: ")
+    key = aespad_key(key)
+    ctext = aes_en(ptext, key)
+    print("Ciphertext:", ctext.hex())
+    print("Decrypted:", aes_de(ctext, key))
+
+if __name__ == '__main__':
+    main()

IS/Lab/Lab2/des.py

@@ -1,23 +1,18 @@
 from Crypto.Cipher import DES
+from Crypto.Util.Padding import pad, unpad
 
 def des_cipher(key):
     return DES.new(key.encode('utf-8'), DES.MODE_ECB)
 
-def despad_ptext(text):
-    n = len(text) % 8
-    if n != 0:
-        return text + (' ' * (8 - n))
-    else:
-        return text
-
 def des_en(ptext, key):
     cipher = des_cipher(key)
-    ptext = despad_ptext(ptext).encode('utf-8')
+    padded_text = pad(ptext.encode('utf-8'), DES.block_size)
-    return cipher.encrypt(ptext)
+    return cipher.encrypt(padded_text)
 
 def des_de(ctext, key):
     cipher = des_cipher(key)
-    return cipher.decrypt(ctext).decode('utf-8').rstrip()
+    decrypted = unpad(cipher.decrypt(ctext), DES.block_size)
+    return decrypted.decode('utf-8')
 
 def despad_key(key):
     return key.ljust(8)[:8]
@@ -25,7 +20,6 @@ def despad_key(key):
 def main():
     print("Welcome to DES (Original)")
     ptext = input("Enter plaintext: ")
-    despad_ptext(ptext)
     key = input("Enter key: ")
     key = despad_key(key)
     ctext = des_en(ptext, key)