def encrypt(cls, key, keyusage, plaintext, confounder):
ki = cls.derive(key, pack('>iB', keyusage, 0x55))
ke = cls.derive(key, pack('>iB', keyusage, 0xAA))
if confounder is None:
confounder = get_random_bytes(cls.blocksize)
basic_plaintext = confounder + _zeropad(plaintext, cls.padsize)
hmac = HMAC_HASH(ki.contents, basic_plaintext, cls.hashalgo)
return cls.basic_encrypt(ke, basic_plaintext) + hmac[:cls.macsize]
def encrypt(cls, key, keyusage, plaintext, confounder):
if confounder is None:
confounder = get_random_bytes(8)
ki = HMAC_HASH(key.contents, cls.usage_str(keyusage), hashes.MD5)
cksum = HMAC_HASH(ki, confounder + plaintext, hashes.MD5)
ke = HMAC_HASH(ki, cksum, hashes.MD5)
encryptor = Cipher(
ciphers.ARC4(ke), None, default_backend()).encryptor()
ctext = encryptor.update(confounder + plaintext)
return cksum + ctext