Added cycle finding function collision generator

cycle_finding_function_collision_generator.py

@@ -0,0 +1,49 @@
+from ethereum.utils import sha3
+import sys
+
+STEPLENGTH = 100
+
+dp = {}
+
+def step(inp):
+    return sha3('function_'+inp.encode('hex')+'()')[:4]
+
+def run_round(inp):
+    orig_inp = inp
+    for i in range(STEPLENGTH):
+        inp = step(inp)
+        if inp in dp.keys():
+            print 'Found!', i + 1, repr(inp)
+            return(True, i + 1, inp)
+    dp[inp] = orig_inp
+    return(False, None, inp)
+
+y = '\xff' * 4
+orig_y = y
+rounds = 0
+while 1:
+    print 'Running round', rounds
+    rounds += 1
+    x, t, y2 = run_round(y)
+    if x:
+        prev1, prev2 = y, dp[y2]
+        assert prev1 != prev2
+        # print '-----'
+        for i in range(STEPLENGTH - t):
+            # print repr(prev2)
+            prev2 = step(prev2) 
+        # print '-----'
+        for i in range(t):
+            # print repr(prev1), repr(prev2)
+            next1 = step(prev1)
+            next2 = step(prev2)
+            if next1 == next2:
+                print 'Found!'
+                print 'function_'+prev1.encode('hex')+'()'
+                print 'function_'+prev2.encode('hex')+'()'
+                sys.exit()
+            prev1, prev2 = next1, next2
+        # print repr(prev1), repr(prev2)
+        raise Exception("Something weird happened")
+    else:
+        y = y2