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# -*- coding: utf-8 -*-
#
# PublicKey/DSA.py : DSA signature primitive
#
# Written in 2008 by Dwayne C. Litzenberger <dlitz@dlitz.net>
#
# ===================================================================
# 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.
# ===================================================================
"""DSA public-key signature algorithm."""
__revision__ = "$Id$"
__all__ = ['generate', 'construct', 'error']
from Crypto.Util.python_compat import *
from Crypto.PublicKey import _DSA, _slowmath, pubkey
from Crypto import Random
try:
from Crypto.PublicKey import _fastmath
except ImportError:
_fastmath = None
class _DSAobj(pubkey.pubkey):
keydata = ['y', 'g', 'p', 'q', 'x']
def __init__(self, implementation, key):
self.implementation = implementation
self.key = key
def __getattr__(self, attrname):
if attrname in self.keydata:
# For backward compatibility, allow the user to get (not set) the
# DSA key parameters directly from this object.
return getattr(self.key, attrname)
else:
raise AttributeError("%s object has no %r attribute" % (self.__class__.__name__, attrname,))
def _encrypt(self, c, K):
raise TypeError("DSA cannot encrypt")
def _decrypt(self, c):
raise TypeError("DSA cannot decrypt")
def _blind(self, m, r):
raise TypeError("DSA cannot blind")
def _unblind(self, m, r):
raise TypeError("DSA cannot unblind")
def _sign(self, m, k):
return self.key._sign(m, k)
def _verify(self, m, sig):
(r, s) = sig
return self.key._verify(m, r, s)
def has_private(self):
return self.key.has_private()
def size(self):
return self.key.size()
def can_blind(self):
return False
def can_encrypt(self):
return False
def can_sign(self):
return True
def publickey(self):
return self.implementation.construct((self.key.y, self.key.g, self.key.p, self.key.q))
def __getstate__(self):
d = {}
for k in self.keydata:
try:
d[k] = getattr(self.key, k)
except AttributeError:
pass
return d
def __setstate__(self, d):
if not hasattr(self, 'implementation'):
self.implementation = DSAImplementation()
t = []
for k in self.keydata:
if not d.has_key(k):
break
t.append(d[k])
self.key = self.implementation._math.dsa_construct(*tuple(t))
def __repr__(self):
attrs = []
for k in self.keydata:
if k == 'p':
attrs.append("p(%d)" % (self.size()+1,))
elif hasattr(self.key, k):
attrs.append(k)
if self.has_private():
attrs.append("private")
return "<%s @0x%x %s>" % (self.__class__.__name__, id(self), ",".join(attrs))
class DSAImplementation(object):
def __init__(self, **kwargs):
# 'use_fast_math' parameter:
# None (default) - Use fast math if available; Use slow math if not.
# True - Use fast math, and raise RuntimeError if it's not available.
# False - Use slow math.
use_fast_math = kwargs.get('use_fast_math', None)
if use_fast_math is None: # Automatic
if _fastmath is not None:
self._math = _fastmath
else:
self._math = _slowmath
elif use_fast_math: # Explicitly select fast math
if _fastmath is not None:
self._math = _fastmath
else:
raise RuntimeError("fast math module not available")
else: # Explicitly select slow math
self._math = _slowmath
self.error = self._math.error
# 'default_randfunc' parameter:
# None (default) - use Random.new().read
# not None - use the specified function
self._default_randfunc = kwargs.get('default_randfunc', None)
self._current_randfunc = None
def _get_randfunc(self, randfunc):
if randfunc is not None:
return randfunc
elif self._current_randfunc is None:
self._current_randfunc = Random.new().read
return self._current_randfunc
def generate(self, bits, randfunc=None, progress_func=None):
# Check against FIPS 186-2, which says that the size of the prime p
# must be a multiple of 64 bits between 512 and 1024
for i in (0, 1, 2, 3, 4, 5, 6, 7, 8):
if bits == 512 + 64*i:
return self._generate(bits, randfunc, progress_func)
# The March 2006 draft of FIPS 186-3 also allows 2048 and 3072-bit
# primes, but only with longer q values. Since the current DSA
# implementation only supports a 160-bit q, we don't support larger
# values.
raise ValueError("Number of bits in p must be a multiple of 64 between 512 and 1024, not %d bits" % (bits,))
def _generate(self, bits, randfunc=None, progress_func=None):
rf = self._get_randfunc(randfunc)
obj = _DSA.generate_py(bits, rf, progress_func) # TODO: Don't use legacy _DSA module
key = self._math.dsa_construct(obj.y, obj.g, obj.p, obj.q, obj.x)
return _DSAobj(self, key)
def construct(self, tup):
key = self._math.dsa_construct(*tup)
return _DSAobj(self, key)
_impl = DSAImplementation()
generate = _impl.generate
construct = _impl.construct
error = _impl.error
# vim:set ts=4 sw=4 sts=4 expandtab:
