From 9b2768d943a452ce6b30c41906ec1aeed495f4b1 Mon Sep 17 00:00:00 2001
From: Andreas Bogk <andreas@pt141.(none)>
Date: Thu, 15 Jan 2009 17:21:19 +0100
Subject: A5/1 implementation in Python by Piotr.

---
 A5.1/python/A51_Tables/table_gen.py | 62 +++++++++++++++++++++++++++++++++++++
 1 file changed, 62 insertions(+)
 create mode 100644 A5.1/python/A51_Tables/table_gen.py

(limited to 'A5.1/python/A51_Tables/table_gen.py')

diff --git a/A5.1/python/A51_Tables/table_gen.py b/A5.1/python/A51_Tables/table_gen.py
new file mode 100644
index 0000000..0e22db3
--- /dev/null
+++ b/A5.1/python/A51_Tables/table_gen.py
@@ -0,0 +1,62 @@
+from a51 import *
+
+class table_gen:
+    def __init__(self, end_point_bit, max_chain_len, max_number_chains):
+        self.end_point_mask = (1 << end_point_bit) - 1
+        self.max_number_chains = max_number_chains
+        self.max_chain_len = max_chain_len
+        self.reduction_function = 0
+
+    def gen(self, reduction_function):
+        self.reduction_function = reduction_function
+        for chain_number in xrange(0,self.max_number_chains):
+            start_point = self._gen_start_point(chain_number)
+            (max_chain_len_exceed, end_point, chain_length) = self._gen_chain(start_point)
+
+            if max_chain_len_exceed == False:    #max_chain_len_exceed is looping
+                print (start_point, end_point, chain_length)
+
+    def _gen_start_point(self, chain_number):
+        start_point = ((chain_number+1) << (18+22))+((chain_number+1) << (18))+(chain_number+1)
+        return start_point  #TODO: find better method to generate start_points of chains
+
+    def _gen_chain(self, start_point): #a5_until_endpoint
+        alg = a51()
+        state = start_point
+        alg.set_state(state)
+
+        print "Generating a chain"
+
+        for chain_links in xrange(0, max_chain_len):
+            output = alg.gen_block(64)
+            print "State:%x -> Output:%x" % (state, output)
+            if self._is_endpoint(output):
+                return (False, output, chain_links)
+
+            state = self._reduction(output)
+            alg.set_state(state)
+
+        return (True, None, None)
+
+    def _is_endpoint(self, output):
+        if (output & self.end_point_mask) == 0:
+            return True
+        else:
+            return False
+
+    def _reduction(self, output):
+        return output ^ self.reduction_function
+
+def gen_tables(max_tables, end_point_bit, max_chain_len, max_number_chains):
+    generator = table_gen(end_point_bit, max_chain_len, max_number_chains)
+    for table_nr in xrange(1,max_tables):
+        reduction_function = table_nr
+        generator.gen(reduction_function)
+
+if __name__ == '__main__':
+    max_tables = 156
+    max_number_chains = 2000
+    end_point_bit = 27
+    max_chain_len = 2000
+
+    gen_tables(max_tables, end_point_bit, max_chain_len, max_number_chains)
-- 
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