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Implementation of AES as used by https://aesencryption.net
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#!/usr/bin/env python3 | |
# -*- coding: utf-8 -*- | |
# | |
# implementation of AES as used by https://aesencryption.net | |
# | |
# (c) 2018 Bernd Busse | |
from cryptography.hazmat.primitives.ciphers import Cipher | |
from cryptography.hazmat.primitives.ciphers.algorithms import AES | |
from cryptography.hazmat.primitives.ciphers.modes import CBC | |
from cryptography.hazmat.backends import default_backend | |
import base64 | |
import sys | |
AES_IV = b'\x31\x32\x33\x34\x35\x36\x37\x38\x62\x30\x7a\x32\x33\x34\x35\x6e' | |
class EncryptionError(RuntimeError): | |
pass | |
class DecryptionError(RuntimeError): | |
pass | |
def usage(executable): | |
sys.stderr.write("usage: {} -e KEY KEYSIZE TEXT\n".format(executable)) | |
sys.stderr.write(" {} -d KEY KEYSIZE CIPHER\n".format(executable)) | |
sys.stderr.flush() | |
def encrypt(password, message, keysize=128): | |
if keysize not in (128, 192, 256): | |
raise EncryptionError( | |
"Invalid key size: {} must be one of (128, 192, 256)" | |
.format(keysize)) | |
aes_key = (password + '\0' * ((keysize // 8) - len(password))).encode("utf-8") | |
cipher = Cipher(algorithm=AES(aes_key[:(keysize // 8)]), | |
mode=CBC(AES_IV), | |
backend=default_backend()) | |
cipher = cipher.encryptor() | |
count = 16 - (len(message) % 16) | |
c_text =cipher.update(message.encode("utf-8")) + cipher.update(count * bytes([count])) + cipher.finalize() | |
return base64.b64encode(c_text).decode("utf-8") | |
def decrypt(password, ciphertext, keysize=128): | |
if keysize not in (128, 192, 256): | |
raise DecryptionError( | |
"Invalid key size: {} must be one of (128, 192, 256)" | |
.format(keysize)) | |
aes_key = (password + '\0' * ((keysize // 8) - len(password))).encode("utf-8") | |
cipher = Cipher(algorithm=AES(aes_key[:(keysize // 8)]), | |
mode=CBC(AES_IV), | |
backend=default_backend()) | |
cipher = cipher.decryptor() | |
message = cipher.update(base64.b64decode(ciphertext)) + cipher.finalize() | |
message = message[:-message[-1]] | |
return message.decode("utf-8") | |
if __name__ == "__main__": | |
if len(sys.argv) != 5: | |
usage(sys.argv[0]) | |
exit(1) | |
if sys.argv[1] == "-e": | |
# Run encryption | |
cipher = encrypt(sys.argv[2], sys.argv[4], keysize=sys.argv[3]) | |
print("Ciphertext: {:s}".format(cipher)) | |
elif sys.argv[1] == "-d": | |
# Run decryption | |
plain = decrypt(sys.argv[2], sys.argv[4], keysize=sys.argv[3]) | |
print("Plaintext: {:s}".format(plain)) | |
else: | |
usage(sys.argv[0]) | |
exit(1) |
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