116 lines
3.5 KiB
Python
116 lines
3.5 KiB
Python
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#
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# DSA.py : Digital Signature Algorithm
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#
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# Part of the Python Cryptography Toolkit
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#
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# Written by Andrew Kuchling, Paul Swartz, and others
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#
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# ===================================================================
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# The contents of this file are dedicated to the public domain. To
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# the extent that dedication to the public domain is not available,
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# everyone is granted a worldwide, perpetual, royalty-free,
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# non-exclusive license to exercise all rights associated with the
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# contents of this file for any purpose whatsoever.
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# No rights are reserved.
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#
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
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# BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
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# ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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# SOFTWARE.
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# ===================================================================
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#
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__revision__ = "$Id$"
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from Crypto.PublicKey.pubkey import *
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from Crypto.Util import number
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from Crypto.Util.number import bytes_to_long, long_to_bytes
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from Crypto.Hash import SHA
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from Crypto.Util.py3compat import *
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class error (Exception):
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pass
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def generateQ(randfunc):
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S=randfunc(20)
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hash1=SHA.new(S).digest()
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hash2=SHA.new(long_to_bytes(bytes_to_long(S)+1)).digest()
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q = bignum(0)
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for i in range(0,20):
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c=bord(hash1[i])^bord(hash2[i])
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if i==0:
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c=c | 128
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if i==19:
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c= c | 1
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q=q*256+c
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while (not isPrime(q)):
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q=q+2
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if pow(2,159) < q < pow(2,160):
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return S, q
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raise RuntimeError('Bad q value generated')
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def generate_py(bits, randfunc, progress_func=None):
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"""generate(bits:int, randfunc:callable, progress_func:callable)
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Generate a DSA key of length 'bits', using 'randfunc' to get
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random data and 'progress_func', if present, to display
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the progress of the key generation.
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"""
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if bits<160:
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raise ValueError('Key length < 160 bits')
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obj=DSAobj()
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# Generate string S and prime q
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if progress_func:
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progress_func('p,q\n')
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while (1):
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S, obj.q = generateQ(randfunc)
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n=divmod(bits-1, 160)[0]
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C, N, V = 0, 2, {}
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b=(obj.q >> 5) & 15
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powb=pow(bignum(2), b)
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powL1=pow(bignum(2), bits-1)
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while C<4096:
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for k in range(0, n+1):
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V[k]=bytes_to_long(SHA.new(S+bstr(N)+bstr(k)).digest())
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W=V[n] % powb
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for k in range(n-1, -1, -1):
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W=(W<<160)+V[k]
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X=W+powL1
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p=X-(X%(2*obj.q)-1)
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if powL1<=p and isPrime(p):
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break
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C, N = C+1, N+n+1
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if C<4096:
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break
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if progress_func:
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progress_func('4096 multiples failed\n')
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obj.p = p
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power=divmod(p-1, obj.q)[0]
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if progress_func:
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progress_func('h,g\n')
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while (1):
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h=bytes_to_long(randfunc(bits)) % (p-1)
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g=pow(h, power, p)
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if 1<h<p-1 and g>1:
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break
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obj.g=g
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if progress_func:
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progress_func('x,y\n')
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while (1):
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x=bytes_to_long(randfunc(20))
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if 0 < x < obj.q:
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break
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obj.x, obj.y = x, pow(g, x, p)
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return obj
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class DSAobj:
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pass
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