2-2-aesformsg.py

from Crypto.Cipher import AES
from Crypto.Hash import SHA256 as SHA


class myAES():
	def __init__(self, keytext, ivtext):
		hash = SHA.new()
		hash.update(keytext.encode('utf-8'))
		key = hash.digest()	
		self.key = key[:16]
		
		hash.update(ivtext.encode('utf-8'))
		iv = hash.digest()
		self.iv = iv[:16]
		
	
	def makeEnabled(self, plaintext):
		fillersize = 0
		textsize = len(plaintext)
		if textsize%16 != 0:
			fillersize = 16-textsize%16
			
		filler = '0'*fillersize
		header = '%d' %(fillersize)
		gap = 16-len(header)
		header += '#'*gap		
		
		return header+plaintext+filler
		

	def enc(self, plaintext):
		plaintext = self.makeEnabled(plaintext)
		aes = AES.new(self.key, AES.MODE_CBC, self.iv)		
		encmsg = aes.encrypt(plaintext.encode())
		return encmsg
		
		
	def dec(self, ciphertext):
		aes = AES.new(self.key, AES.MODE_CBC, self.iv)
		decmsg = aes.decrypt(ciphertext)
		
		header = decmsg[:16].decode()
		fillersize = int(header.split('#')[0])
		if fillersize != 0:
			decmsg = decmsg[16:-fillersize]
			
		return decmsg


def main():
	keytext = 'samsjang'
	iv = '1234'
	#msg = 'python35'
	msg = 'python35ab'
	
	myCipher = myAES(keytext, iv)	
	ciphered = myCipher.enc(msg)	
	deciphered = myCipher.dec(ciphered)
	print('ORIGINAL:\t%s' %msg)
	print('CIPHERED:\t%s' %ciphered)
	print('DECIPHERED:\t%s' %deciphered)

if __name__ == '__main__':
	main()