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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
10import time
11
12# Sets the constant for block's size to 16
13BLOCK_SIZE = 16
14
15# Sets the current directory to 'src' so it can run on all systems
16os.chdir(os.path.dirname(os.path.realpath(__file__)))
17
18# This is used when encoding plaintext when about to encrypt with AES
19def pad(size):
20    return size + (BLOCK_SIZE - len(size) % BLOCK_SIZE) * chr(BLOCK_SIZE - len(size) % BLOCK_SIZE)
21
22# Used to decode the ciphertext after it has been decoded with the secret key
23def reverse_pad(size):
24    return size[:-ord(size[len(size) - 1:])]
25
26# This is used to get text when it is called from any of the Get Functions below
27def get_text_from_file(filename):
28    my_file = open(filename)
29    file_text = my_file.read().replace('\n', '')
30    my_file.close()
31    return file_text
32
33# ----------------------------------------------------------------------------
34# All "Get" functions obtain the file's text drom the data folder when called
35def get_secret_key():
36    return get_text_from_file('../data/key.txt')
37
38def get_plaintext():
39    return get_text_from_file('../data/plaintext.txt')
40
41def get_ciphertext():
42    return get_text_from_file('../data/ciphertext.txt')
43
44def get_randomized_iv():
45    hex_str = get_text_from_file('../data/iv.txt')
46    return binascii.unhexlify(hex_str)
47# ----------------------------------------------------------------------------
48
49# Creates and returns a randomized IV
50def create_randomized_iv():
51    iv = Random.new().read(BLOCK_SIZE)
52    my_file = open('../data/iv.txt', 'w')
53    my_file.write(iv.hex())
54    my_file.close()
55    return iv
56
57# Creates and returns a randomized secret key
58def generate_key():
59    secret_key = hashlib.sha256(os.urandom(16)).digest()
60    my_file = open('../data/key.txt', 'w')
61    my_file.write(secret_key.hex())
62    my_file.close()
63    return secret_key
64
65# --- Encryption Function ---
66# Inputs: secret key, plaintext message
67# Outputs: ciphertext from provided secret key and message
68def encryption(key, plaintext, mode):
69    iv = create_randomized_iv()
70    ciphertext = AES.new(key, mode, iv).encrypt(pad(plaintext)).hex()
71    my_file = open('../data/ciphertext.txt', 'w')
72    my_file.write(ciphertext)
73    my_file.close()
74    return ciphertext
75
76# Encrypts plaintext using ECB with no writing to any files
77def enc_for_ecb(key, plaintext):
78    return encryption(key, plaintext, AES.MODE_ECB)
79
80# Encrypts plaintext using CBC with no writing to any files
81def enc_for_cbc(key, plaintext):
82    return encryption(key, plaintext, AES.MODE_CBC)
83
84# --- Decryption Function ---
85# Inputs: secret key, ciphertext, IV, and a mode type (CBC or ECB)
86# Outputs: decrypted ciphertext and stores value in appropriate file
87def decryption(key, ciphertext, iv, mode):
88    temp_cipher = AES.new(key, mode, iv)
89    plaintext_dec = reverse_pad(temp_cipher.decrypt(binascii.unhexlify(ciphertext))).decode('utf-8')
90    my_file = open('../data/result.txt', 'w')
91    my_file.write(plaintext_dec)
92    my_file.close()
93    return plaintext_dec
94
95def compare_aes_enc_modes():
96    for i in range(0, 3):
97        secret_key = generate_key()
98        plaintext = get_plaintext()
99        ecb_enc = enc_for_ecb(secret_key, plaintext)
100        cdc_enc = enc_for_ecb(secret_key, plaintext)
101        print('Encrptyion Rounnd ' + str(i+1))
102        print('Enc with ECB: ' + ecb_enc)
103        print('Enc with CBC: ' + cbc_enc)
104        print('\n')
105
106
107
108# ---------------------- Displayed output begins here ----------------------
109secret_key = generate_key()
110# EBC
111print('\n')
112ecb_enc = encryption(secret_key, get_plaintext(), AES.MODE_ECB)
113ecb_dec = decryption(secret_key, ecb_enc, get_randomized_iv(), AES.MODE_ECB)
114print('Encrypted with ECB: ' + ecb_enc)
115print('Decrypted with ECB: ' + ecb_dec)
116
117# CBC
118print('\n')
119cbc_enc = encryption(secret_key, get_plaintext(), AES.MODE_CBC)
120cbc_dec = decryption(secret_key, cbc_enc, get_randomized_iv(), AES.MODE_CBC)
121print('Enc with CBC: ' + cbc_enc)
122print('Decrypt with CBC: ' + cbc_dec)
123
124print('\n')
125compare_aes_enc_modes()
126print('\n')
127# ---------------------- End of output ----------------------
128# start of timing test
129time_vec = 0
130for i in range(0, 10000):
131    start = time.time()
132    cbc_enc = encryption(secret_key, get_plaintext(), AES.MODE_CBC)
133    end = time.time()
134    time_vec += (end-start)*1000 # convert to milliseconds
135
136average_enc_time = time_vec / 10000
137print("Average # of milliseconds elapsed for Encryption of 10000 samples: " + str(average_enc_time))
138
139time_vec2 = 0
140for i in range(0, 10000):
141    start = time.time()
142    cbc_dec = decryption(secret_key, cbc_enc, get_randomized_iv(), AES.MODE_CBC)
143    end = time.time()
144    time_vec2 += (end-start)*1000 # convert to milliseconds
145
146average_enc_time = time_vec2 / 10000
147print("Average # of milliseconds elapsed for Decryption of 10000 samples: " + str(average_enc_time))