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#
# pubkey.py : Internal functions for public key operations
#
# Part of the Python Cryptography Toolkit
#
# Written by Andrew Kuchling, Paul Swartz, and others
#
# ===================================================================
# The contents of this file are dedicated to the public domain. To
# the extent that dedication to the public domain is not available,
# everyone is granted a worldwide, perpetual, royalty-free,
# non-exclusive license to exercise all rights associated with the
# contents of this file for any purpose whatsoever.
# No rights are reserved.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
# BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
# ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.
# ===================================================================
#
__revision__ = "$Id$"
import types, warnings
from Crypto.Util.number import *
# Basic public key class
class pubkey:
"""An abstract class for a public key object.
:undocumented: __getstate__, __setstate__, __eq__, __ne__, validate
"""
def __init__(self):
pass
def __getstate__(self):
"""To keep key objects platform-independent, the key data is
converted to standard Python long integers before being
written out. It will then be reconverted as necessary on
restoration."""
d=self.__dict__
for key in self.keydata:
if d.has_key(key): d[key]=long(d[key])
return d
def __setstate__(self, d):
"""On unpickling a key object, the key data is converted to the big
number representation being used, whether that is Python long
integers, MPZ objects, or whatever."""
for key in self.keydata:
if d.has_key(key): self.__dict__[key]=bignum(d[key])
def encrypt(self, plaintext, K):
"""Encrypt a piece of data.
:Parameter plaintext: The piece of data to encrypt.
:Type plaintext: byte string or long
:Parameter K: A random parameter required by some algorithms
:Type K: byte string or long
:Return: A tuple with two items. Each item is of the same type as the
plaintext (string or long).
"""
wasString=0
if isinstance(plaintext, types.StringType):
plaintext=bytes_to_long(plaintext) ; wasString=1
if isinstance(K, types.StringType):
K=bytes_to_long(K)
ciphertext=self._encrypt(plaintext, K)
if wasString: return tuple(map(long_to_bytes, ciphertext))
else: return ciphertext
def decrypt(self, ciphertext):
"""Decrypt a piece of data.
:Parameter ciphertext: The piece of data to decrypt.
:Type ciphertext: byte string, long or a 2-item tuple as returned by `encrypt`
:Return: A byte string if ciphertext was a byte string or a tuple
of byte strings. A long otherwise.
"""
wasString=0
if not isinstance(ciphertext, types.TupleType):
ciphertext=(ciphertext,)
if isinstance(ciphertext[0], types.StringType):
ciphertext=tuple(map(bytes_to_long, ciphertext)) ; wasString=1
plaintext=self._decrypt(ciphertext)
if wasString: return long_to_bytes(plaintext)
else: return plaintext
def sign(self, M, K):
"""Sign a piece of data.
:Parameter M: The piece of data to encrypt.
:Type M: byte string or long
:Parameter K: A random parameter required by some algorithms
:Type K: byte string or long
:Return: A tuple with two items.
"""
if (not self.has_private()):
raise TypeError('Private key not available in this object')
if isinstance(M, types.StringType): M=bytes_to_long(M)
if isinstance(K, types.StringType): K=bytes_to_long(K)
return self._sign(M, K)
def verify (self, M, signature):
"""Verify the validity of a signature.
:Parameter M: The expected message.
:Type M: byte string or long
:Parameter signature: The signature to verify.
:Type signature: tuple with two items, as return by `sign`
:Return: True if the signature is correct, False otherwise.
"""
if isinstance(M, types.StringType): M=bytes_to_long(M)
return self._verify(M, signature)
# alias to compensate for the old validate() name
def validate (self, M, signature):
warnings.warn("validate() method name is obsolete; use verify()",
DeprecationWarning)
def blind(self, M, B):
"""Blind a message to prevent certain side-channel attacks.
:Parameter M: The message to blind.
:Type M: byte string or long
:Parameter B: Blinding factor.
:Type B: byte string or long
:Return: A byte string if M was so. A long otherwise.
"""
wasString=0
if isinstance(M, types.StringType):
M=bytes_to_long(M) ; wasString=1
if isinstance(B, types.StringType): B=bytes_to_long(B)
blindedmessage=self._blind(M, B)
if wasString: return long_to_bytes(blindedmessage)
else: return blindedmessage
def unblind(self, M, B):
"""Unblind a message after cryptographic processing.
:Parameter M: The encoded message to unblind.
:Type M: byte string or long
:Parameter B: Blinding factor.
:Type B: byte string or long
"""
wasString=0
if isinstance(M, types.StringType):
M=bytes_to_long(M) ; wasString=1
if isinstance(B, types.StringType): B=bytes_to_long(B)
unblindedmessage=self._unblind(M, B)
if wasString: return long_to_bytes(unblindedmessage)
else: return unblindedmessage
# The following methods will usually be left alone, except for
# signature-only algorithms. They both return Boolean values
# recording whether this key's algorithm can sign and encrypt.
def can_sign (self):
"""Tell if the algorithm can deal with cryptographic signatures.
This property concerns the *algorithm*, not the key itself.
It may happen that this particular key object hasn't got
the private information required to generate a signature.
:Return: boolean
"""
return 1
def can_encrypt (self):
"""Tell if the algorithm can deal with data encryption.
This property concerns the *algorithm*, not the key itself.
It may happen that this particular key object hasn't got
the private information required to decrypt data.
:Return: boolean
"""
return 1
def can_blind (self):
"""Tell if the algorithm can deal with data blinding.
This property concerns the *algorithm*, not the key itself.
It may happen that this particular key object hasn't got
the private information required carry out blinding.
:Return: boolean
"""
return 0
# The following methods will certainly be overridden by
# subclasses.
def size (self):
"""Tell the maximum number of bits that can be handled by this key.
:Return: int
"""
return 0
def has_private (self):
"""Tell if the key object contains private components.
:Return: bool
"""
return 0
def publickey (self):
"""Construct a new key carrying only the public information.
:Return: A new `pubkey` object.
"""
return self
def __eq__ (self, other):
"""__eq__(other): 0, 1
Compare us to other for equality.
"""
return self.__getstate__() == other.__getstate__()
def __ne__ (self, other):
"""__ne__(other): 0, 1
Compare us to other for inequality.
"""
return not self.__eq__(other)
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