new 7 simmetric

ecryption.py

@@ -1,4 +1,89 @@
+import random
+
+STRING = "A Londoner was going to the west of England for a holiday. \
+He arrived at a small town by train. When he knew that there were two hotels there, \
+he took a taxi. On the way out of the station he asked the driver: «How long have \
+you been living here?» «Since childhood,» — was the answer. «Then which hotel could \
+you recommend?» asked the tourist. «You see, it makes no difference — whichever hotel \
+you’ll choose you’ll be sorry you didn’t choose the other,» answered the driver."
+MUL = 200
+
 def encrypt(k, m):
-    return ''.join(map(chr, [x + k for x in map(ord, m)]))
+    return ''.join(map(chr, [(x + k) % 65536 for x in map(ord, m)]))
+
+def decrypt(k, c):
+    return ''.join(map(chr, [(x - k) % 65536 for x in map(ord, c)]))
+
+encrypted = encrypt(2, STRING)
+print("-"*MUL)
+print(encrypted)
+print("-"*MUL)
+decrypted = decrypt(2, encrypted)
+print(decrypted)
+print("-"*MUL)
+
+def auto_decrypter(text):
+    container = []
+    for el in set(text):
+        container.append((el, text.count(el)))
+    container.sort(key = lambda x:x[1] , reverse = True)
+    shifts = [ord(" ") - ord(el[0]) for el in container]
+    for shift in shifts:
+        decrypted = encrypt(shift, text)
+        print(decrypted)
+        cmd = input("Если текст читаем - введите любой символ, иначе Enter!   ")
+        if cmd:
+            return shift
+
+    return None
+
+print("Свдиг: ", - auto_decrypter(encrypted))
+print("-"*MUL)
+
+def encrypt_Vernam(text, key = None):
+    text_len = len(text)
+    if not key:
+        key = ''.join([chr(random.randint(0,65535)) for _ in range(text_len)])
+    encrypted_text = ''.join([chr(ord(text[i])^ord(key[i])) for i in range(text_len)])
+    return encrypted_text, key
+
+encrypted, key = encrypt_Vernam(STRING)
+decrypted, key = encrypt_Vernam(encrypted, key)
+print(decrypted)
+print("-"*MUL)
+
+def encode_CPC(text, key = None, vector = None):
+    if key:
+        block_size = len(key)
+    else:
+        block_size= 32
+        key = ''.join([chr(random.randint(0,65535)) for _ in range(block_size)])
+    if not vector or (len(vector) != block_size):
+        vector = ''.join([chr(random.randint(0,65535)) for _ in range(block_size)])
+    return cipher_block_chaining(text, key, vector), key, vector
+
+
+def cipher_block_chaining(text, key, vector):
+    if not text:
+        return ""
+    block_size = len(key)
+    summary_text = encrypt_Vernam(text[:block_size], vector)[0]
+    encrypted = encrypt_Vernam(summary_text, key)[0]
+    return encrypted + cipher_block_chaining(text[block_size:], key, encrypted)
+
+def decode_CPC(encrypted, key, vector):
+    if not encrypted:
+        return ""
+    block_size = len(key)
+    block = len(encrypted) % block_size
+    block = block_size if not block else block
+    summary_text = encrypt_Vernam(encrypted[-block:], key)[0]
+    previous_vector = vector if len(encrypted) <= block_size else encrypted[- block - block_size: - block]
+    decrypted = encrypt_Vernam(summary_text, previous_vector)[0]
+    return decode_CPC(encrypted[:-block], key, vector) + decrypted
+
 
-print(encrypt(2, 'Hello!'))
+encrypted, key, vector = encode_CPC(STRING)
+decrypted = decode_CPC(encrypted, key, vector)
+print(decrypted)
+print("-"*MUL)