diff options
Diffstat (limited to 'docs/hazmat/primitives/asymmetric')
| -rw-r--r-- | docs/hazmat/primitives/asymmetric/padding.rst | 22 | ||||
| -rw-r--r-- | docs/hazmat/primitives/asymmetric/rsa.rst | 89 |
2 files changed, 109 insertions, 2 deletions
diff --git a/docs/hazmat/primitives/asymmetric/padding.rst b/docs/hazmat/primitives/asymmetric/padding.rst index 89af7eaa..40084799 100644 --- a/docs/hazmat/primitives/asymmetric/padding.rst +++ b/docs/hazmat/primitives/asymmetric/padding.rst @@ -19,7 +19,8 @@ Padding PSS (Probabilistic Signature Scheme) is a signature scheme defined in :rfc:`3447`. It is more complex than PKCS1 but possesses a `security proof`_. - This is the `recommended padding algorithm`_ for RSA signatures. + This is the `recommended padding algorithm`_ for RSA signatures. It cannot + be used with RSA encryption. :param mgf: A mask generation function object. At this time the only supported MGF is :class:`MGF1`. @@ -32,12 +33,28 @@ Padding Pass this attribute to ``salt_length`` to get the maximum salt length available. +.. class:: OAEP(mgf, label) + + .. versionadded:: 0.4 + + OAEP (Optimal Asymmetric Encryption Padding) is a padding scheme defined in + :rfc:`3447`. It provides probabilistic encryption and is `proven secure`_ + against several attack types. This is the `recommended padding algorithm`_ + for RSA encryption. It cannot be used with RSA signing. + + :param mgf: A mask generation function object. At this time the only + supported MGF is :class:`MGF1`. + + :param bytes label: A label to apply. This is a rarely used field and + should typically be set to ``None`` or ``b""``, which are equivalent. + .. class:: PKCS1v15() .. versionadded:: 0.3 PKCS1 v1.5 (also known as simply PKCS1) is a simple padding scheme - developed for use with RSA keys. It is defined in :rfc:`3447`. + developed for use with RSA keys. It is defined in :rfc:`3447`. This padding + can be used for signing and encryption. Mask generation functions ~~~~~~~~~~~~~~~~~~~~~~~~~ @@ -60,3 +77,4 @@ Mask generation functions .. _`Padding is critical`: http://rdist.root.org/2009/10/06/why-rsa-encryption-padding-is-critical/ .. _`security proof`: http://eprint.iacr.org/2001/062.pdf .. _`recommended padding algorithm`: http://www.daemonology.net/blog/2009-06-11-cryptographic-right-answers.html +.. _`proven secure`: http://cseweb.ucsd.edu/users/mihir/papers/oae.pdf diff --git a/docs/hazmat/primitives/asymmetric/rsa.rst b/docs/hazmat/primitives/asymmetric/rsa.rst index 5074f1c5..862df635 100644 --- a/docs/hazmat/primitives/asymmetric/rsa.rst +++ b/docs/hazmat/primitives/asymmetric/rsa.rst @@ -116,6 +116,60 @@ RSA :raises ValueError: This is raised when the chosen hash algorithm is too large for the key size. + .. method:: decrypt(ciphertext, padding, backend) + + .. versionadded:: 0.4 + + Decrypt data that was encrypted with the public key. + + :param bytes ciphertext: The ciphertext to decrypt. + + :param padding: An instance of a + :class:`~cryptography.hazmat.primitives.interfaces.AsymmetricPadding` + provider. + + :param backend: A + :class:`~cryptography.hazmat.backends.interfaces.RSABackend` + provider. + + :return bytes: Decrypted data. + + :raises cryptography.exceptions.UnsupportedAlgorithm: This is raised if + the provided ``backend`` does not implement + :class:`~cryptography.hazmat.backends.interfaces.RSABackend` or if + the backend does not support the chosen hash or padding algorithm. + If the padding is + :class:`~cryptography.hazmat.primitives.asymmetric.padding.OAEP` + with the + :class:`~cryptography.hazmat.primitives.asymmetric.padding.MGF1` + mask generation function it may also refer to the ``MGF1`` hash + algorithm. + + :raises TypeError: This is raised when the padding is not an + :class:`~cryptography.hazmat.primitives.interfaces.AsymmetricPadding` + provider. + + :raises ValueError: This is raised when decryption fails or the data + is too large for the key size. If the padding is + :class:`~cryptography.hazmat.primitives.asymmetric.padding.OAEP` + it may also be raised for invalid label values. + + .. code-block:: python + + from cryptography.hazmat.backends import default_backend + from cryptography.hazmat.primitives import hashes + from cryptography.hazmat.primitives.asymmetric import padding + + plaintext = private_key.decrypt( + ciphertext, + padding.OAEP( + mgf=padding.MGF1(algorithm=hashes.SHA1()), + algorithm=hashes.SHA1(), + label=None + ), + default_backend() + ) + .. class:: RSAPublicKey(public_exponent, modulus) @@ -214,7 +268,42 @@ RSA too large for the key size. +Handling partial RSA private keys +--------------------------------- + +If you are trying to load RSA private keys yourself you may find that not all +parameters required by ``RSAPrivateKey`` are available. In particular the +`Chinese Remainder Theorem`_ (CRT) values ``dmp1``, ``dmq1``, ``iqmp`` may be +missing or present in a different form. For example `OpenPGP`_ does not include +the ``iqmp``, ``dmp1`` or ``dmq1`` parameters. + +The following functions are provided for users who want to work with keys like +this without having to do the math themselves. + +.. function:: rsa_crt_iqmp(p, q) + + .. versionadded:: 0.4 + + Generates the ``iqmp`` (also known as ``qInv``) parameter from the RSA + primes ``p`` and ``q``. + +.. function:: rsa_crt_dmp1(private_exponent, p) + + .. versionadded:: 0.4 + + Generates the ``dmp1`` parameter from the RSA private exponent and prime + ``p``. + +.. function:: rsa_crt_dmq1(private_exponent, q) + + .. versionadded:: 0.4 + + Generates the ``dmq1`` parameter from the RSA private exponent and prime + ``q``. + .. _`RSA`: https://en.wikipedia.org/wiki/RSA_(cryptosystem) .. _`public-key`: https://en.wikipedia.org/wiki/Public-key_cryptography .. _`use 65537`: http://www.daemonology.net/blog/2009-06-11-cryptographic-right-answers.html .. _`at least 2048`: http://www.ecrypt.eu.org/documents/D.SPA.20.pdf +.. _`OpenPGP`: https://en.wikipedia.org/wiki/Pretty_Good_Privacy +.. _`Chinese Remainder Theorem`: http://en.wikipedia.org/wiki/RSA_%28cryptosystem%29#Using_the_Chinese_remainder_algorithm |