reversed word dictionary matching

src/matching.coffee

@@ -96,6 +96,7 @@ matching =
     matches = []
     matchers = [
       @dictionary_match
+      @reverse_dictionary_match
       @l33t_match
       @spatial_match
       @repeat_match
@@ -130,6 +131,20 @@ matching =
               matched_word: word
               rank: rank
               dictionary_name: dictionary_name
+              reversed: false
+    @sorted matches
+
+  reverse_dictionary_match: (password, _ranked_dictionaries = RANKED_DICTIONARIES) ->
+    reversed_password = password.split('').reverse().join('')
+    matches = @dictionary_match reversed_password, _ranked_dictionaries
+    for match in matches
+      match.token = match.token.split('').reverse().join('') # reverse back
+      match.reversed = true
+      # map coordinates back to original string
+      [match.i, match.j] = [
+        password.length - 1 - match.j
+        password.length - 1 - match.i
+      ]
     @sorted matches
 
   set_user_input_dictionary: (ordered_list) ->

src/scoring.coffee

@@ -228,8 +228,9 @@ scoring =
   dictionary_entropy: (match) ->
     match.base_entropy = @lg match.rank # keep these as properties for display purposes
     match.uppercase_entropy = @extra_uppercase_entropy match
-    match.l33t_entropy = @extra_l33t_entropy match
-    match.base_entropy + match.uppercase_entropy + match.l33t_entropy
+    match.reversed_entropy = match.reversed and 1 or 0
+    match.l33t_entropy = @extra_l33t_entropy(match)
+    match.base_entropy + match.uppercase_entropy + match.l33t_entropy + match.reversed_entropy
 
   START_UPPER: /^[A-Z][^A-Z]+$/
   END_UPPER: /^[^A-Z]+[A-Z]$/

test/test-matching.coffee

@@ -188,6 +188,24 @@ test 'dictionary matching', (t) ->
   t.end()
 
 
+test 'reverse dictionary matching', (t) ->
+  test_dicts =
+    d1:
+      123: 1
+      321: 2
+      456: 3
+      654: 4
+  password = '0123456789'
+  matches = matching.reverse_dictionary_match password, test_dicts
+  msg = 'matches against reversed words'
+  check_matches msg, t, matches, 'dictionary', ['123', '456'], [[1, 3], [4, 6]],
+    matched_word: ['321', '654']
+    reversed: [true, true]
+    dictionary_name: ['d1', 'd1']
+    rank: [2, 4]
+  t.end()
+
+
 test 'l33t matching', (t) ->
   test_table =
     a: ['4', '@']

test/test-scoring.coffee

@@ -342,6 +342,13 @@ test 'dictionary_entropy', (t) ->
   msg = "extra entropy is added for capitalization"
   t.equal scoring.dictionary_entropy(match), lg(32) + scoring.extra_uppercase_entropy(match), msg
 
+  match =
+    token: 'aaa'
+    rank: 32
+    reversed: true
+  msg = "1 bit of extra entropy is added for reversed words"
+  t.equal scoring.dictionary_entropy(match), lg(32) + 1, msg
+
   match =
     token: 'aaa@@@'
     rank: 32