# Here we can encrypt a, for example, Word document using two different methods and decrypt it.

# Open my selected file: "First News File: The Australian Case":

file = open('R#_data.docx','rb')

content = file.read()

content

# Create new file to write original data into it:

file_out = open('New_R#_data.docx','wb')

doc = file_out.write(content)

# source: https://python-docx.readthedocs.io/en/latest/user/documents.html

# source: https://automatetheboringstuff.com/chapter13/

############################

### PART 1 - DATA DIGEST ###

############################

# Method 1: Using SHA 256 to Hash the file:

from Crypto.Hash import SHA256

hash_M1 = SHA256.new(data=content)

print(hash_M1.digest())

# b'\xf6\xddpY\xae\xb4R\xe6Hl\xc0W]Y]V?@y\x1fBL\xf3GS\xb6\xbc\x0e\xacax2'

print(hash_M1.hexdigest())

# f6dd7059aeb452e6486cc0575d595d563f40791f424cf34753b6bc0eac617832

# source: https://pycryptodome.readthedocs.io/en/latest/src/hash/sha256.html

# source: https://nitratine.net/blog/post/how-to-hash-files-in-python/

# Method 2: Using BLAKE2S to Hash the file:

from Crypto.Hash import BLAKE2s

hash_M2 = BLAKE2s.new(digest_bits=256)

hash_M2.update(content)

print(hash_M2.digest())

# b'\xa6\xd4\xd9c\x80mP\xd1\x88\xbd[\xbcm\xebYr{\xb9\x1fU\x0b\xdf\x9bc\xaf\x05\x80\xef8\x92\xa1\x81'

print(hash_M2.hexdigest())

# a6d4d963806d50d188bd5bbc6deb59727bb91f550bdf9b63af0580ef3892a181

# source: https://pycryptodome.readthedocs.io/en/latest/src/hash/blake2s.html

# source: https://nitratine.net/blog/post/how-to-hash-files-in-python/

################################

### PART 2 - DATA ENCRYPTION ###

################################

# Method 1: Encrypting using AES (CBC):

from Crypto.Cipher import AES

from Crypto.Util.Padding import pad

output_file = 'R#_AES.bin' # Output file

data = content # data doc

key = b'!SQS5342_LBO@S_B' # The key you generated

# Create cipher object and encrypt the data

cipher = AES.new(key, AES.MODE_CBC) # Create a AES cipher object with the key using the mode CBC

ciphered_data = cipher.encrypt(pad(data, AES.block_size)) # Pad the input data and then encrypt

file_out = open(output_file, "wb") # Open file to write bytes

file_out.write(cipher.iv) # Write the iv to the output file (will be required for decryption)

file_out.write(ciphered_data) # Write the varying length cipher text to the file (this is the encrypted data)

file_out.close()

# source: https://pycryptodome.readthedocs.io/en/latest/src/cipher/classic.html

# source: https://pycryptodome.readthedocs.io/en/latest/src/cipher/aes.html

# source: https://nitratine.net/blog/post/python-encryption-and-decryption-with-pycryptodome/

# Method 2: Encrypting using CAST Mode:

from Crypto.Cipher import CAST

output_file = 'R#_CAST.bin'

data = content

key = b'!SQS5342_LBO@S_B'

cipher = CAST.new(key, CAST.MODE_OPENPGP)

plaintext = content

msg = cipher.encrypt(plaintext)

file_out = open(output_file, "wb") # Open file to write bytes

#file_out.write(cipher.iv) # Write the iv to the output file (will be required for decryption)

file_out.write(ciphered_data) # Write the varying length cipher text to the file (this is the encrypted data)

file_out.close()

# source: https://pycryptodome.readthedocs.io/en/latest/src/cipher/cast.html

################################

### PART 3 - DATA DECRYPTION ###

################################

# Method 1: Decrypting Using AES (CBC):

from Crypto.Util.Padding import unpad

input_file = 'R#_AES.bin' # Input file

key = b'!SQS5342_LBO@S_B' # The key used for encryption (do not store/read this from the file)

# Read the data from the file

file_in = open(input_file, 'rb') # Open the file to read bytes

iv = file_in.read(16) # Read the iv out - this is 16 bytes long

ciphered_data = file_in.read() # Read the rest of the data

file_in.close()

cipher = AES.new(key, AES.MODE_CBC, iv=iv) # Setup cipher

original_data = unpad(cipher.decrypt(ciphered_data), AES.block_size) # Decrypt and then up-pad the result

file_out = open('R#_AES_decrypted.docx','wb')

doc1 = file_out.write(original_data)

assert content == original_data

# source: # https://nitratine.net/blog/post/python-encryption-and-decryption-with-pycryptodome/

# Method 2: Decrypting using CAST Mode:

input_file = 'R#_CAST.bin'

key = b'!SQS5342_LBO@S_B'

eiv = msg[:CAST.block_size+2]

ciphertext = msg[CAST.block_size+2:]

cipher = CAST.new(key, CAST.MODE_OPENPGP, eiv)

cast_D = cipher.decrypt(ciphertext)

file_out2 = open('R#_CAST_decrypted.docx','wb')

doc2 = file_out2.write(cast_D)

# source: https://pycryptodome.readthedocs.io/en/latest/src/cipher/cast.html

###########################################

### PART 4: Data Integrity Verification ###

###########################################

# Method 1: Using SHA 256 to Hash the Decrypted file:

from Crypto.Hash import SHA256

hash_D1 = SHA256.new(data=original_data) # from decryption

print(hash_D1.digest())

# Original file:

# b'\xf6\xddpY\xae\xb4R\xe6Hl\xc0W]Y]V?@y\x1fBL\xf3GS\xb6\xbc\x0e\xacax2'

# Decrypted file:

# b'\xf6\xddpY\xae\xb4R\xe6Hl\xc0W]Y]V?@y\x1fBL\xf3GS\xb6\xbc\x0e\xacax2'

print(hash_D1.hexdigest())

# Original file:

# f6dd7059aeb452e6486cc0575d595d563f40791f424cf34753b6bc0eac617832

# Decrypted file:

# f6dd7059aeb452e6486cc0575d595d563f40791f424cf34753b6bc0eac617832

# source: https://pycryptodome.readthedocs.io/en/latest/src/hash/hash.html

# Method 2: Using BLAKE2S to Hash the Decrypted file:

from Crypto.Hash import BLAKE2s

hash_D2 = BLAKE2s.new(digest_bits=256)

hash_D2.update(original_data)

print(hash_D2.digest())

# Original file:

# b'\xa6\xd4\xd9c\x80mP\xd1\x88\xbd[\xbcm\xebYr{\xb9\x1fU\x0b\xdf\x9bc\xaf\x05\x80\xef8\x92\xa1\x81'

# Decrypted file:

# b'\xa6\xd4\xd9c\x80mP\xd1\x88\xbd[\xbcm\xebYr{\xb9\x1fU\x0b\xdf\x9bc\xaf\x05\x80\xef8\x92\xa1\x81'

print(hash_D2.hexdigest())

# Original file:

# a6d4d963806d50d188bd5bbc6deb59727bb91f550bdf9b63af0580ef3892a181

# Decrypted:

# a6d4d963806d50d188bd5bbc6deb59727bb91f550bdf9b63af0580ef3892a181