def reencrypt(
self, rekey: Tuple[tuple, Tuple[bytes,
bytes]], ciphertext: Tuple[bytes,
bytes]
) -> Tuple[Tuple[bytes, bytes], Tuple[bytes, bytes]]:
"""
Re-encrypt for public key
rekey is (rk, encrypted_eph), same as output of rekey()
ciphertext is a tuple in the same format as output of encrypt()
Output is two tuples: data encrypted with an ephemeral key
and the ephemeral private key encrypted for recepient (Bob)
"""
rk, encrypted_eph = rekey
rk = umbral.RekeyFrag(rk[0],
ec.deserialize(self.pre.ecgroup, rk[1]),
pre=PRE)
ekey, edata = ciphertext
ekey = umbral.EncryptedKey(ekey=ec.deserialize(self.pre.ecgroup,
ekey[0]),
re_id=ekey[1])
ekey = self.pre.reencrypt(rk, ekey)
ekey = (ec.serialize(ekey.ekey), ekey.re_id)
return (ekey, edata), encrypted_eph
def decrypt(self,
edata: Tuple[bytes, bytes],
privkey: bytes = None) -> bytes:
"""
Decrypt data encrypted by ECIES
edata = (ekey, edata)
ekey is needed to reconstruct a DH secret
edata encrypted by the block cipher
privkey is optional private key if we want to use something else
than what keypair uses
"""
if isinstance(edata[0], tuple) and isinstance(edata[1], tuple):
# In case it was re-encrypted data
return self.decrypt_reencrypted(edata)
ekey, edata = edata
# When it comes to decrypt(), ekey[1] is always None
# we could use that and save 2 bytes,
# but it makes the code less readable
ekey = umbral.EncryptedKey(ekey=ec.deserialize(API.PRE.ecgroup,
ekey[0]),
re_id=ekey[1])
if privkey is None:
privkey = self._priv_key
else:
privkey = ec.deserialize(API.PRE.ecgroup, privkey)
key = self.pre.decapsulate(privkey, ekey)
cipher = SecretBox(key)
return cipher.decrypt(edata)
def combine(self,
shares: Tuple[Tuple[bytes, bytes], Tuple[bytes, bytes]]
) -> Tuple[Tuple[bytes, bytes], Tuple[bytes, bytes]]:
ekeys = [umbral.EncryptedKey(
ekey=ec.deserialize(self.pre.ecgroup, share[0][0][0]),
re_id=share[0][0][1])
for share in shares]
ekey = self.pre.combine(ekeys)
ekey = (ec.serialize(ekey.ekey), ekey.re_id)
# Everything except ekey is the same for all shares!
# TODO instead of trusting the first share, trust the majority
return (ekey, shares[0][0][1]), shares[0][1]
def ecies_reencrypt(
rekey: Union[bytes, umbral.RekeyFrag],
enc_key: Union[bytes, umbral.EncryptedKey],
) -> umbral.EncryptedKey:
"""
Re-encrypts the key provided.
:param rekey: Re-encryption key to use
:param enc_key: Encrypted key to re-encrypt
:return: The re-encrypted key
"""
if type(rekey) == bytes:
rekey = umbral.RekeyFrag(None, priv_bytes2ec(rekey))
if type(enc_key) == bytes:
enc_key = umbral.EncryptedKey(priv_bytes2ec(enc_key), None)
return PRE.reencrypt(rekey, enc_key)
