basic functionalty

modules/Crypto/PublicKey/_DSA.py

@@ -0,0 +1,115 @@
+
+#
+#   DSA.py : Digital Signature Algorithm
+#
+#  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__ = "$Id$"
+
+from Crypto.PublicKey.pubkey import *
+from Crypto.Util import number
+from Crypto.Util.number import bytes_to_long, long_to_bytes
+from Crypto.Hash import SHA1
+from Crypto.Util.py3compat import *
+
+class error (Exception):
+    pass
+
+def generateQ(randfunc):
+    S=randfunc(20)
+    hash1=SHA1.new(S).digest()
+    hash2=SHA1.new(long_to_bytes(bytes_to_long(S)+1)).digest()
+    q = bignum(0)
+    for i in range(0,20):
+        c=bord(hash1[i])^bord(hash2[i])
+        if i==0:
+            c=c | 128
+        if i==19:
+            c= c | 1
+        q=q*256+c
+    while (not isPrime(q)):
+        q=q+2
+    if pow(2,159L) < q < pow(2,160L):
+        return S, q
+    raise RuntimeError('Bad q value generated')
+
+def generate_py(bits, randfunc, progress_func=None):
+    """generate(bits:int, randfunc:callable, progress_func:callable)
+
+    Generate a DSA key of length 'bits', using 'randfunc' to get
+    random data and 'progress_func', if present, to display
+    the progress of the key generation.
+    """
+
+    if bits<160:
+        raise ValueError('Key length < 160 bits')
+    obj=DSAobj()
+    # Generate string S and prime q
+    if progress_func:
+        progress_func('p,q\n')
+    while (1):
+        S, obj.q = generateQ(randfunc)
+        n=divmod(bits-1, 160)[0]
+        C, N, V = 0, 2, {}
+        b=(obj.q >> 5) & 15
+        powb=pow(bignum(2), b)
+        powL1=pow(bignum(2), bits-1)
+        while C<4096:
+            for k in range(0, n+1):
+                V[k]=bytes_to_long(SHA1.new(S+bstr(N)+bstr(k)).digest())
+            W=V[n] % powb
+            for k in range(n-1, -1, -1):
+                W=(W<<160L)+V[k]
+            X=W+powL1
+            p=X-(X%(2*obj.q)-1)
+            if powL1<=p and isPrime(p):
+                break
+            C, N = C+1, N+n+1
+        if C<4096:
+            break
+        if progress_func:
+            progress_func('4096 multiples failed\n')
+
+    obj.p = p
+    power=divmod(p-1, obj.q)[0]
+    if progress_func:
+        progress_func('h,g\n')
+    while (1):
+        h=bytes_to_long(randfunc(bits)) % (p-1)
+        g=pow(h, power, p)
+        if 1<h<p-1 and g>1:
+            break
+    obj.g=g
+    if progress_func:
+        progress_func('x,y\n')
+    while (1):
+        x=bytes_to_long(randfunc(20))
+        if 0 < x < obj.q:
+            break
+    obj.x, obj.y = x, pow(g, x, p)
+    return obj
+
+class DSAobj:
+    pass
+