Ленгауэр Артём ПИ20-3 Шифрование

Lab_work8.py

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+# 1) Написать функцию шифрования и дешифрования текста обобщенным шифром Цезаря.
+
+#import modules
+from typing import Counter
+
+print('\nРезультаты работы функций\n')
+
+#Examle of data to encrypt
+string = 'h e ll o world'
+
+#Enter your key here
+key = 2
+
+#encryption function
+def encrypt(key, data):
+
+    max = 65536
+    min = 0
+
+    #create list of coded letters
+    list_of_numbers = []
+    for letter in data:
+        code_letter = ord(letter)
+        list_of_numbers.append(code_letter)
+
+    #add key to each number
+    for number in range(len(list_of_numbers)):
+        #check for max number
+        if (list_of_numbers[number] + key) > max:
+            number_add = min #!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+            number_add = key - (max-list_of_numbers[number])
+            list_of_numbers[number] = min
+            list_of_numbers[number] += number_add
+        else:
+            list_of_numbers[number] = list_of_numbers[number] + key 
+
+    #transform list of numbers back into string
+    result = ''
+    for number in list_of_numbers:
+        result = result + str(chr(number))
+
+    return result
+
+#Decryption function
+def decrypt(key, data):
+
+    max = 65536
+    min = 0
+
+    #create list of coded letters
+    list_of_numbers_to_decode = []
+    for letter in data:
+        code_letter = ord(letter)
+        list_of_numbers_to_decode.append(code_letter)
+
+    #subtract key from each number
+    for number in range(len(list_of_numbers_to_decode)):
+        #check for min number
+        if (list_of_numbers_to_decode[number] - key) < min:
+            number_substract = key - list_of_numbers_to_decode[number]
+            list_of_numbers_to_decode[number] = max - number_substract
+        else:
+            list_of_numbers_to_decode[number] = list_of_numbers_to_decode[number] - key
+
+    #transform list of numbers back into string
+    result = ''
+    for number in list_of_numbers_to_decode:
+        result = result + str(chr(number))
+
+    return result
+
+#Examle of data to decrypt (In this case it is a data for back encrypted text to normal)
+string2 = encrypt(key,string)
+
+print('1 задание (Написать функцию шифрования и дешифрования текста обобщенным шифром Цезаря.)')
+print('Initial text: ', string)
+print('Encrypted text: ', encrypt(key,string))
+print('Decrypted text: ', decrypt(key,string2))
+
+
+
+
+
+# 2) Написать функцию, принимающую шифротекст, зашифрованный шифром из предыдущего задания и восстанавливающий текст, без знания ключа.
+
+string_to_hack = encrypt(key,string)
+
+
+#Function to hack encrypted text
+def Hack(data):
+    #find the most common element
+    counter = {}
+    for i in data: 
+        counter[i] = counter.get(i, 0) + 1
+    most_common_element = sorted([ (freq,word) for word, freq in counter.items() ], reverse=True)[:1][0][1]
+    number_of_the_most_common_element = ord(most_common_element)
+
+    #number of space
+    space = 32
+
+    #calculate key
+    key = number_of_the_most_common_element - space
+
+    return key
+
+print('\n2 задание (Написать функцию, принимающую шифротекст, зашифрованный шифром из предыдущего задания и восстанавливающий текст, без знания ключа.)')
+print('Encrypted text: ', string_to_hack)
+print('Decrypted text: ', decrypt(Hack(string_to_hack), string_to_hack) ) #Hack(string_to_hack) - key; string_to_hack - encrypted text
+
+
+
+
+#3)Реализовать в виде функций шифр Вернама.
+
+#Function to encrypt text
+def Ver1_enc(key, data):
+    key = key * (len(data) // len(key)) + key[:(len(data) % len(key))]
+    return ''.join(map(chr, [i ^ x for i, x in zip(map(ord, data), map(ord, key))]))
+
+#Function to decrypt texxt
+def Ver2_dec(key, data):
+    return Ver1_enc(key, data)
+
+#Vernam key
+ver_key = "1 2 6 4 3"
+
+#initial Vernam text
+ver_data = 'hello '
+
+#encrypted  Vernam text
+ver_data_enc = Ver1_enc(ver_key,ver_data)
+
+print('\n3 задание (Реализовать в виде функций шифр Вернама.)')
+print('inintial Vernam text: ', ver_data)
+print('encrypted Vernam text: ', Ver1_enc(ver_key,ver_data))
+print('decrypted Vernam text: ', Ver2_dec(ver_key, ver_data_enc))