X-Git-Url: https://git.njae.me.uk/?a=blobdiff_plain;f=cipherbreak.py;h=0ac8ae57f7ed11a443dfedc8366ddc51086eda8c;hb=a9d938167b636e599586ebbc5aeec75c877e120f;hp=b1af48c2e40d1ba60b948e75c758ab162f242233;hpb=14ac787d794684b5aceacb307d687597e464e7b4;p=cipher-tools.git

diff --git a/cipherbreak.py b/cipherbreak.py
index b1af48c..0ac8ae5 100644
--- a/cipherbreak.py
+++ b/cipherbreak.py
@@ -199,23 +199,27 @@ def keyword_break_worker(message, keyword, wrap_alphabet, fitness):
     return (keyword, wrap_alphabet), fit
 
 def monoalphabetic_break_hillclimbing(message, max_iterations=10000000, 
-        fitness=Pletters):
+        alphabet=None, fitness=Pletters):
     ciphertext = unaccent(message).lower()
-    alphabet = list(string.ascii_lowercase)
-    random.shuffle(alphabet)
-    alphabet = ''.join(alphabet)
+    if not alphabet:
+        alphabet = list(string.ascii_lowercase)
+        random.shuffle(alphabet)
+        alphabet = ''.join(alphabet)
     return monoalphabetic_break_hillclimbing_worker(ciphertext, alphabet,
                                                     max_iterations, fitness)
 
 def monoalphabetic_break_hillclimbing_mp(message, workers=10, 
-        max_iterations = 10000000, fitness=Pletters, chunksize=1):
+        max_iterations = 10000000, alphabet=None, fitness=Pletters, chunksize=1):
     worker_args = []
     ciphertext = unaccent(message).lower()
     for i in range(workers):
-        alphabet = list(string.ascii_lowercase)
-        random.shuffle(alphabet)
-        alphabet = ''.join(alphabet)
-        worker_args.append((ciphertext, alphabet, max_iterations, fitness))
+        if alphabet:
+            this_alphabet = alphabet
+        else:
+            this_alphabet = list(string.ascii_lowercase)
+            random.shuffle(this_alphabet)
+            this_alphabet = ''.join(this_alphabet)
+        worker_args.append((ciphertext, this_alphabet, max_iterations, fitness))
     with Pool() as pool:
         breaks = pool.starmap(monoalphabetic_break_hillclimbing_worker,
                               worker_args, chunksize)
@@ -464,6 +468,64 @@ def railfence_break(message, max_key_length=20,
                                for i in range(2, max_key_length+1)])
     return max(results, key=lambda k: k[1])
 
+def amsco_break(message, translist=transpositions, patterns = [(1, 2), (2, 1)],
+                                  fillstyles = [AmscoFillStyle.continuous, 
+                                                AmscoFillStyle.same_each_row, 
+                                                AmscoFillStyle.reverse_each_row],
+                                  fitness=Pbigrams, 
+                                  chunksize=500):
+    """Breaks an AMSCO transposition cipher using a dictionary and
+    n-gram frequency analysis
+
+    >>> amsco_break(amsco_transposition_encipher(sanitise( \
+            "It is a truth universally acknowledged, that a single man in \
+             possession of a good fortune, must be in want of a wife. However \
+             little known the feelings or views of such a man may be on his \
+             first entering a neighbourhood, this truth is so well fixed in \
+             the minds of the surrounding families, that he is considered the \
+             rightful property of some one or other of their daughters."), \
+        'encipher'), \
+        translist={(2, 0, 5, 3, 1, 4, 6): ['encipher'], \
+                   (5, 0, 6, 1, 3, 4, 2): ['fourteen'], \
+                   (6, 1, 0, 4, 5, 3, 2): ['keyword']}, \
+        patterns=[(1, 2)]) # doctest: +ELLIPSIS
+    (((2, 0, 5, 3, 1, 4, 6), (1, 2)), -709.4646722...)
+    >>> amsco_break(amsco_transposition_encipher(sanitise( \
+            "It is a truth universally acknowledged, that a single man in \
+             possession of a good fortune, must be in want of a wife. However \
+             little known the feelings or views of such a man may be on his \
+             first entering a neighbourhood, this truth is so well fixed in \
+             the minds of the surrounding families, that he is considered the \
+             rightful property of some one or other of their daughters."), \
+        'encipher', fillpattern=(2, 1)), \
+        translist={(2, 0, 5, 3, 1, 4, 6): ['encipher'], \
+                   (5, 0, 6, 1, 3, 4, 2): ['fourteen'], \
+                   (6, 1, 0, 4, 5, 3, 2): ['keyword']}, \
+        patterns=[(1, 2), (2, 1)], fitness=Ptrigrams) # doctest: +ELLIPSIS
+    (((2, 0, 5, 3, 1, 4, 6), (2, 1)), -997.0129085...)
+    """
+    with Pool() as pool:
+        helper_args = [(message, trans, pattern, fillstyle, fitness)
+                       for trans in translist.keys()
+                       for pattern in patterns
+                       for fillstyle in fillstyles]
+        # Gotcha: the helper function here needs to be defined at the top level
+        #   (limitation of Pool.starmap)
+        breaks = pool.starmap(amsco_break_worker, helper_args, chunksize) 
+        return max(breaks, key=lambda k: k[1])
+
+def amsco_break_worker(message, transposition,
+        pattern, fillstyle, fitness):
+    plaintext = amsco_transposition_decipher(message, transposition,
+        fillpattern=pattern, fillstyle=fillstyle)
+    fit = fitness(sanitise(plaintext))
+    logger.debug('AMSCO transposition break attempt using key {0} and pattern'
+                         '{1} ({2}) gives fit of {3} and decrypt starting: '
+                         '{4}'.format(
+                             transposition, pattern, fillstyle, fit, 
+                             sanitise(plaintext)[:50]))
+    return (transposition, pattern, fillstyle), fit
+
 
 def hill_break(message, matrix_size=2, fitness=Pletters, 
     number_of_solutions=1, chunksize=500):