Source code for nacl.public

# Copyright 2013 Donald Stufft and individual contributors
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# See the License for the specific language governing permissions and
# limitations under the License.
from __future__ import absolute_import
from __future__ import division

import nacl.c
import nacl.c.crypto_box

from nacl import encoding
from nacl.utils import EncryptedMessage, StringFixer, random

[docs]class PublicKey(encoding.Encodable, StringFixer, object): """ The public key counterpart to an Curve25519 :class:`nacl.public.PrivateKey` for encrypting messages. :param public_key: [:class:`bytes`] Encoded Curve25519 public key :param encoder: A class that is able to decode the `public_key` :cvar SIZE: The size that the public key is required to be """ SIZE = nacl.c.crypto_box_PUBLICKEYBYTES def __init__(self, public_key, encoder=encoding.RawEncoder): self._public_key = encoder.decode(public_key) if len(self._public_key) != self.SIZE: raise ValueError("The public key must be exactly %s bytes long" % self.SIZE) def __bytes__(self): return self._public_key
[docs]class PrivateKey(encoding.Encodable, StringFixer, object): """ Private key for decrypting messages using the Curve25519 algorithm. .. warning:: This **must** be protected and remain secret. Anyone who knows the value of your :class:`~nacl.public.PrivateKey` can decrypt any message encrypted by the corresponding :class:`~nacl.public.PublicKey` :param private_key: The private key used to decrypt messages :param encoder: The encoder class used to decode the given keys :cvar SIZE: The size that the private key is required to be """ SIZE = nacl.c.crypto_box_SECRETKEYBYTES def __init__(self, private_key, encoder=encoding.RawEncoder): # Decode the secret_key private_key = encoder.decode(private_key) # Verify that our seed is the proper size if len(private_key) != self.SIZE: raise ValueError( "The secret key must be exactly %d bytes long" % self.SIZE) raw_public_key = nacl.c.crypto_scalarmult_base(private_key) self._private_key = private_key self.public_key = PublicKey(raw_public_key) def __bytes__(self): return self._private_key @classmethod
[docs] def generate(cls): """ Generates a random :class:`~nacl.public.PrivateKey` object :rtype: :class:`~nacl.public.PrivateKey` """ return cls(random(PrivateKey.SIZE), encoder=encoding.RawEncoder)
[docs]class Box(encoding.Encodable, StringFixer, object): """ The Box class boxes and unboxes messages between a pair of keys The ciphertexts generated by :class:`~nacl.public.Box` include a 16 byte authenticator which is checked as part of the decryption. An invalid authenticator will cause the decrypt function to raise an exception. The authenticator is not a signature. Once you've decrypted the message you've demonstrated the ability to create arbitrary valid message, so messages you send are repudiable. For non-repudiable messages, sign them after encryption. :param private_key: :class:`~nacl.public.PrivateKey` used to encrypt and decrypt messages :param public_key: :class:`~nacl.public.PublicKey` used to encrypt and decrypt messages :cvar NONCE_SIZE: The size that the nonce is required to be. """ NONCE_SIZE = nacl.c.crypto_box_NONCEBYTES def __init__(self, private_key, public_key): if private_key and public_key: self._shared_key = nacl.c.crypto_box_beforenm( private_key.encode(encoder=encoding.RawEncoder), public_key.encode(encoder=encoding.RawEncoder), ) else: self._shared_key = None def __bytes__(self): return self._shared_key @classmethod def decode(cls, encoded, encoder=encoding.RawEncoder): # Create an empty box box = cls(None, None) # Assign our decoded value to the shared key of the box box._shared_key = encoder.decode(encoded) return box
[docs] def encrypt(self, plaintext, nonce, encoder=encoding.RawEncoder): """ Encrypts the plaintext message using the given `nonce` and returns the ciphertext encoded with the encoder. .. warning:: It is **VITALLY** important that the nonce is a nonce, i.e. it is a number used only once for any given key. If you fail to do this, you compromise the privacy of the messages encrypted. :param plaintext: [:class:`bytes`] The plaintext message to encrypt :param nonce: [:class:`bytes`] The nonce to use in the encryption :param encoder: The encoder to use to encode the ciphertext :rtype: [:class:`nacl.utils.EncryptedMessage`] """ if len(nonce) != self.NONCE_SIZE: raise ValueError("The nonce must be exactly %s bytes long" % self.NONCE_SIZE) ciphertext = nacl.c.crypto_box_afternm( self._shared_key, plaintext, nonce, ) encoded_nonce = encoder.encode(nonce) encoded_ciphertext = encoder.encode(ciphertext) return EncryptedMessage._from_parts( encoded_nonce, encoded_ciphertext, encoder.encode(nonce + ciphertext), )
[docs] def decrypt(self, ciphertext, nonce=None, encoder=encoding.RawEncoder): """ Decrypts the ciphertext using the given nonce and returns the plaintext message. :param ciphertext: [:class:`bytes`] The encrypted message to decrypt :param nonce: [:class:`bytes`] The nonce used when encrypting the ciphertext :param encoder: The encoder used to decode the ciphertext. :rtype: [:class:`bytes`] """ # Decode our ciphertext ciphertext = encoder.decode(ciphertext) if nonce is None: # If we were given the nonce and ciphertext combined, split them. nonce = ciphertext[:self.NONCE_SIZE] ciphertext = ciphertext[self.NONCE_SIZE:] if len(nonce) != self.NONCE_SIZE: raise ValueError("The nonce must be exactly %s bytes long" % self.NONCE_SIZE) plaintext = nacl.c.crypto_box_open_afternm( self._shared_key, ciphertext, nonce, ) return plaintext