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Diffstat (limited to 'frozen_deps/Crypto/PublicKey/DSA.py')
| -rw-r--r-- | frozen_deps/Crypto/PublicKey/DSA.py | 379 |
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diff --git a/frozen_deps/Crypto/PublicKey/DSA.py b/frozen_deps/Crypto/PublicKey/DSA.py new file mode 100644 index 0000000..648f4b2 --- /dev/null +++ b/frozen_deps/Crypto/PublicKey/DSA.py @@ -0,0 +1,379 @@ +# -*- 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. + +DSA_ is a widespread public-key signature algorithm. Its security is +based on the discrete logarithm problem (DLP_). Given a cyclic +group, a generator *g*, and an element *h*, it is hard +to find an integer *x* such that *g^x = h*. The problem is believed +to be difficult, and it has been proved such (and therefore secure) for +more than 30 years. + +The group is actually a sub-group over the integers modulo *p*, with *p* prime. +The sub-group order is *q*, which is prime too; it always holds that *(p-1)* is a multiple of *q*. +The cryptographic strength is linked to the magnitude of *p* and *q*. +The signer holds a value *x* (*0<x<q-1*) as private key, and its public +key (*y* where *y=g^x mod p*) is distributed. + +In 2012, a sufficient size is deemed to be 2048 bits for *p* and 256 bits for *q*. +For more information, see the most recent ECRYPT_ report. + +DSA is reasonably secure for new designs. + +The algorithm can only be used for authentication (digital signature). +DSA cannot be used for confidentiality (encryption). + +The values *(p,q,g)* are called *domain parameters*; +they are not sensitive but must be shared by both parties (the signer and the verifier). +Different signers can share the same domain parameters with no security +concerns. + +The DSA signature is twice as big as the size of *q* (64 bytes if *q* is 256 bit +long). + +This module provides facilities for generating new DSA keys and for constructing +them from known components. DSA keys allows you to perform basic signing and +verification. + + >>> from Crypto.Random import random + >>> from Crypto.PublicKey import DSA + >>> from Crypto.Hash import SHA + >>> + >>> message = "Hello" + >>> key = DSA.generate(1024) + >>> h = SHA.new(message).digest() + >>> k = random.StrongRandom().randint(1,key.q-1) + >>> sig = key.sign(h,k) + >>> ... + >>> if key.verify(h,sig): + >>> print "OK" + >>> else: + >>> print "Incorrect signature" + +.. _DSA: http://en.wikipedia.org/wiki/Digital_Signature_Algorithm +.. _DLP: http://www.cosic.esat.kuleuven.be/publications/talk-78.pdf +.. _ECRYPT: http://www.ecrypt.eu.org/documents/D.SPA.17.pdf +""" + +__revision__ = "$Id$" + +__all__ = ['generate', 'construct', 'error', 'DSAImplementation', '_DSAobj'] + +import sys +if sys.version_info[0] == 2 and sys.version_info[1] == 1: + from Crypto.Util.py21compat 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): + """Class defining an actual DSA key. + + :undocumented: __getstate__, __setstate__, __repr__, __getattr__ + """ + #: Dictionary of DSA parameters. + #: + #: A public key will only have the following entries: + #: + #: - **y**, the public key. + #: - **g**, the generator. + #: - **p**, the modulus. + #: - **q**, the order of the sub-group. + #: + #: A private key will also have: + #: + #: - **x**, the private key. + 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 sign(self, M, K): + """Sign a piece of data with DSA. + + :Parameter M: The piece of data to sign with DSA. It may + not be longer in bit size than the sub-group order (*q*). + :Type M: byte string or long + + :Parameter K: A secret number, chosen randomly in the closed + range *[1,q-1]*. + :Type K: long (recommended) or byte string (not recommended) + + :attention: selection of *K* is crucial for security. Generating a + random number larger than *q* and taking the modulus by *q* is + **not** secure, since smaller values will occur more frequently. + Generating a random number systematically smaller than *q-1* + (e.g. *floor((q-1)/8)* random bytes) is also **not** secure. In general, + it shall not be possible for an attacker to know the value of `any + bit of K`__. + + :attention: The number *K* shall not be reused for any other + operation and shall be discarded immediately. + + :attention: M must be a digest cryptographic hash, otherwise + an attacker may mount an existential forgery attack. + + :Return: A tuple with 2 longs. + + .. __: http://www.di.ens.fr/~pnguyen/pub_NgSh00.htm + """ + return pubkey.pubkey.sign(self, M, K) + + def verify(self, M, signature): + """Verify the validity of a DSA signature. + + :Parameter M: The expected message. + :Type M: byte string or long + + :Parameter signature: The DSA signature to verify. + :Type signature: A tuple with 2 longs as return by `sign` + + :Return: True if the signature is correct, False otherwise. + """ + return pubkey.pubkey.verify(self, M, signature) + + 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 k not in d: + 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") + # PY3K: This is meant to be text, do not change to bytes (data) + return "<%s @0x%x %s>" % (self.__class__.__name__, id(self), ",".join(attrs)) + +class DSAImplementation(object): + """ + A DSA key factory. + + This class is only internally used to implement the methods of the + `Crypto.PublicKey.DSA` module. + """ + + def __init__(self, **kwargs): + """Create a new DSA key factory. + + :Keywords: + use_fast_math : bool + Specify which mathematic library to use: + + - *None* (default). Use fastest math available. + - *True* . Use fast math. + - *False* . Use slow math. + default_randfunc : callable + Specify how to collect random data: + + - *None* (default). Use Random.new().read(). + - not *None* . Use the specified function directly. + :Raise RuntimeError: + When **use_fast_math** =True but fast math is not available. + """ + 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): + """Randomly generate a fresh, new DSA key. + + :Parameters: + bits : int + Key length, or size (in bits) of the DSA modulus + *p*. + It must be a multiple of 64, in the closed + interval [512,1024]. + randfunc : callable + Random number generation function; it should accept + a single integer N and return a string of random data + N bytes long. + If not specified, a new one will be instantiated + from ``Crypto.Random``. + progress_func : callable + Optional function that will be called with a short string + containing the key parameter currently being generated; + it's useful for interactive applications where a user is + waiting for a key to be generated. + + :attention: You should always use a cryptographically secure random number generator, + such as the one defined in the ``Crypto.Random`` module; **don't** just use the + current time and the ``random`` module. + + :Return: A DSA key object (`_DSAobj`). + + :Raise ValueError: + When **bits** is too little, too big, or not a multiple of 64. + """ + + # 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): + """Construct a DSA key from a tuple of valid DSA components. + + The modulus *p* must be a prime. + + The following equations must apply: + + - p-1 = 0 mod q + - g^x = y mod p + - 0 < x < q + - 1 < g < p + + :Parameters: + tup : tuple + A tuple of long integers, with 4 or 5 items + in the following order: + + 1. Public key (*y*). + 2. Sub-group generator (*g*). + 3. Modulus, finite field order (*p*). + 4. Sub-group order (*q*). + 5. Private key (*x*). Optional. + + :Return: A DSA key object (`_DSAobj`). + """ + 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: + |