Start of an RSABackend interface
Only has key generation for now.
diff --git a/docs/hazmat/backends/interfaces.rst b/docs/hazmat/backends/interfaces.rst
index 5131ca1..444ecb4 100644
--- a/docs/hazmat/backends/interfaces.rst
+++ b/docs/hazmat/backends/interfaces.rst
@@ -191,3 +191,24 @@
the derived key. This is typically a password.
:return bytes: Derived key.
+
+
+.. class:: RSABackend
+
+ .. versionadded:: 0.2
+
+ A backend with methods for using RSA.
+
+ .. method:: generate_rsa_private_key(public_exponent, bit_length)
+
+ :param int public_exponent: The public exponent of the new key.
+ Often one of the small Fermat primes 3, 5, 17, 257 or 65537.
+
+ :param int bit_length: The length in bits of the modulus. Should be
+ at least 2048.
+
+ :return: A new instance of a
+ :class:`~cryptography.hazmat.primitives.interfaces.RSAPrivateKey`
+ provider.
+
+ :raises ValueError: If the public_exponent is not valid.