How to Create an Encryption Program with Python

How to Create an Encryption Program with Python?


from Crypto.Hash import SHA256
from Crypto.Cipher import AES
import os, random, sys, pkg_resources

def encrypt(key, filename):
chunksize = 64 * 1024
outFile = os.path.join(os.path.dirname(filename), "(encrypted)"+os.path.basename(filename))
filesize = str(os.path.getsize(filename)).zfill(16)
IV = ''

for i in range(16):
IV += chr(random.randint(0, 0xFF))

encryptor = AES.new(key, AES.MODE_CBC, IV)

with open(filename, "rb") as infile:
with open(outFile, "wb") as outfile:
outfile.write(filesize)
outfile.write(IV)
while True:
chunk = infile.read(chunksize)

if len(chunk) == 0:
break

elif len(chunk) % 16 !=0:
chunk += ' ' *  (16 - (len(chunk) % 16))

outfile.write(encryptor.encrypt(chunk))


def decrypt(key, filename):
outFile = os.path.join(os.path.dirname(filename), os.path.basename(filename[11:]))
chunksize = 64 * 1024
with open(filename, "rb") as infile:
filesize = infile.read(16)
IV = infile.read(16)

decryptor = AES.new(key, AES.MODE_CBC, IV)

with open(outFile, "wb") as outfile:
while True:
chunk = infile.read(chunksize)
if len(chunk) == 0:
break

outfile.write(decryptor.decrypt(chunk))

outfile.truncate(int(filesize))

def allfiles():
allFiles = []
for root, subfiles, files in os.walk(os.getcwd()):
for names in files:
allFiles.append(os.path.join(root, names))

return allFiles


choice = raw_input("Do you want to (E)ncrypt or (D)ecrypt? ")
password = raw_input("Enter the password: ")

encFiles = allfiles()

if choice == "E":
for Tfiles in encFiles:
if os.path.basename(Tfiles).startswith("(encrypted)"):
print "%s is already encrypted" %str(Tfiles)
pass

elif Tfiles == os.path.join(os.getcwd(), sys.argv[0]):
pass
else:
encrypt(SHA256.new(password).digest(), str(Tfiles))
print "Done encrypting %s" %str(Tfiles)
os.remove(Tfiles)


elif choice == "D":
filename = raw_input("Enter the filename to decrypt: ")
if not os.path.exists(filename):
print "The file does not exist"
sys.exit(0)
elif not filename.startswith("(encrypted)"):
print "%s is already not encrypted" %filename
sys.exit()
else:
decrypt(SHA256.new(password).digest(), filename)
print "Done decrypting %s" %filename
os.remove(filename)

else:
print "Please choose a valid command."
sys.exit()


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