ZRbpEGhu

1# Ryan Finley
2# 3/8/2018
3# AesEncryption.py
4
5import os
6import binascii
7import hashlib
8from Crypto import Random
9from Crypto.Cipher import AES
10
11# Sets the constant for block's size to 16
12BLOCK_SIZE = 16
13
14# Sets the current directory to 'src' so it can run on all systems
15os.chdir(os.path.dirname(os.path.realpath(__file__)))
16
17# This is used when encoding plaintext when about to encrypt with AES
18def pad(size):
19    return size + (BLOCK_SIZE - len(size) % BLOCK_SIZE) * chr(BLOCK_SIZE - len(size) % BLOCK_SIZE)
20
21# Used to decode the ciphertext after it has been decoded with the secret key
22def reverse_pad(size):
23    return size[:-ord(size[len(size) - 1:])]
24
25# This is used to get text when it is called from any of the Get Functions below
26def get_text_from_file(filename):
27    my_file = open(filename)
28    file_text = my_file.read().replace('\n', '')
29    my_file.close()
30    return file_text
31
32# ----------------------------------------------------------------------------
33# All "Get" functions obtain the file's text drom the data folder when called
34def get_secret_key():
35    return get_text_from_file('../data/key.txt')
36
37def get_plaintext():
38    return get_text_from_file('../data/plaintext.txt')
39
40def get_ciphertext():
41    return get_text_from_file('../data/ciphertext.txt')
42
43def get_randomized_iv():
44    hex_str = get_text_from_file('../data/iv.txt')
45    return binascii.unhexlify(hex_str)
46# ----------------------------------------------------------------------------
47
48# Creates and returns a randomized IV
49def create_randomized_iv():
50    iv = Random.new().read(BLOCK_SIZE)
51    my_file = open('../data/iv.txt', 'w')
52    my_file.write(iv.hex())
53    my_file.close()
54    return iv
55
56# Creates and returns a randomized secret key
57def generate_key():
58    secret_key = hashlib.sha256(os.urandom(16)).digest()
59    my_file = open('../data/key.txt', 'w')
60    my_file.write(secret_key.hex())
61    my_file.close()
62    return secret_key
63
64# --- Encryption Function ---
65# Inputs: secret key, plaintext message
66# Outputs: ciphertext from provided secret key and message
67def encryption(key, plaintext, mode):
68    iv = create_randomized_iv()
69    ciphertext = AES.new(key, mode, iv).encrypt(pad(plaintext)).hex()
70    my_file = open('../data/ciphertext.txt', 'w')
71    my_file.write(ciphertext)
72    my_file.close()
73    return ciphertext
74
75# Encrypts plaintext using ECB and CBC and stores each in a separate varaible
76# They are then returned as a tuple
77def enc_all(key, plaintext):
78    ecb_enc = encryption(key, plaintext, AES.MODE_ECB)
79    cbc_enc = encryption(key, plaintext, AES.MODE_CBC)
80    return (ecb_enc, cbc_enc)
81
82# --- Decryption Function ---
83# Inputs: secret key, ciphertext, IV, and a mode type (CBC or ECB)
84# Outputs: decrypted ciphertext and stores value in appropriate file
85def decryption(key, ciphertext, iv, mode):
86    temp_cipher = AES.new(key, mode, iv)
87    plaintext_dec = reverse_pad(temp_cipher.decrypt(binascii.unhexlify(ciphertext))).decode('utf-8')
88    my_file = open('../data/result.txt', 'w')
89    my_file.write(plaintext_dec)
90    my_file.close()
91    return plaintext_dec
92
93# Decrypts the 2 ciphertexts it recieves in the form of a tuple and returns them
94def decrypt_all(key, ciphertexts, iv):
95    (ecb, cbc) = ciphertexts
96    ecb_dec = decryption(key, ciphertext, iv, AES.MODE_ECB)
97    cbc_dec = decryption(key, ciphertext, iv, AES.MODE_CBC)
98    return (ecb_dec, cbc_dec)
99
100
101def compare_aes_enc_modes():
102    for i in range(0, 3):
103        sk = generate_key()
104        plaintext = get_plaintext()
105        (ecb_enc, cbc_enc) = enc_all(sk, plaintext)
106        print('Encrptyion Rounnd ' + str(i+1))
107        print('Enc with ECB: ' + ecb_enc)
108        print('Enc with CBC: ' + cbc_enc)
109        print('\n')
110
111sk = generate_key()
112
113# ---------------------- Displayed output begins here ----------------------
114# EBC
115print('\n')
116ecb_enc = encryption(sk, get_plaintext(), AES.MODE_ECB)
117ecb_dec = decryption(sk, ecb_enc, get_randomized_iv(), AES.MODE_ECB)
118print('Encrypted with ECB: ' + ecb_enc)
119print('Decrypted with ECB: ' + ecb_dec)
120
121# CBC
122print('\n')
123cbc_enc = encryption(sk, get_plaintext(), AES.MODE_CBC)
124cbc_dec = decryption(sk, cbc_enc, get_randomized_iv(), AES.MODE_CBC)
125print('Enc with CBC: ' + cbc_enc)
126print('Decrypt with CBC: ' + cbc_dec)
127
128print('\n')
129compare_aes_enc_modes()
130print('\n')