Help wanted with md2 hash algorithm

wjb131 at web.de wjb131 at web.de
Fri Jan 6 23:54:50 CET 2006


hi all,

below you find my simple python version of MD2 algorithm
as described in RFC1319  (http://rfc1319.x42.com/MD2).
It produces correct results for strings shorter than 16 Bytes and wrong
results for longer strings.

I can't find what's wrong.

Can anybody help?

Regards
Wolfgang

-------------------------------------

#--- MD2 validation data
md2_test = [
   ('', '8350e5a3e24c153df2275c9f80692773'),
   ("a", '32ec01ec4a6dac72c0ab96fb34c0b5d1'),
   ("abc", 'da853b0d3f88d99b30283a69e6ded6bb'),
   ("message digest", 'ab4f496bfb2a530b219ff33031fe06b0'),
   ("abcdefghijklmnopqrstuvwxyz",
    '4e8ddff3650292ab5a4108c3aa47940b'),
   ("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789",
    'da33def2a42df13975352846c30338cd'),

("12345678901234567890123456789012345678901234567890123456789012345678901234567890",

    'd5976f79d83d3a0dc9806c3c66f3efd8' )
    ]


#--- 256-byte "random" permutation constructed from the digits of pi
PI_SUBST = [41, 46, 67, 201, 162, 216, 124, 1, 61, 54, 84, 161, 236,
240, 6,
  19, 98, 167, 5, 243, 192, 199, 115, 140, 152, 147, 43, 217, 188,
  76, 130, 202, 30, 155, 87, 60, 253, 212, 224, 22, 103, 66, 111, 24,
  138, 23, 229, 18, 190, 78, 196, 214, 218, 158, 222, 73, 160, 251,
  245, 142, 187, 47, 238, 122, 169, 104, 121, 145, 21, 178, 7, 63,
  148, 194, 16, 137, 11, 34, 95, 33, 128, 127, 93, 154, 90, 144, 50,
  39, 53, 62, 204, 231, 191, 247, 151, 3, 255, 25, 48, 179, 72, 165,
  181, 209, 215, 94, 146, 42, 172, 86, 170, 198, 79, 184, 56, 210,
  150, 164, 125, 182, 118, 252, 107, 226, 156, 116, 4, 241, 69, 157,
  112, 89, 100, 113, 135, 32, 134, 91, 207, 101, 230, 45, 168, 2, 27,
  96, 37, 173, 174, 176, 185, 246, 28, 70, 97, 105, 52, 64, 126, 15,
  85, 71, 163, 35, 221, 81, 175, 58, 195, 92, 249, 206, 186, 197,
  234, 38, 44, 83, 13, 110, 133, 40, 132, 9, 211, 223, 205, 244, 65,
  129, 77, 82, 106, 220, 55, 200, 108, 193, 171, 250, 36, 225, 123,
  8, 12, 189, 177, 74, 120, 136, 149, 139, 227, 99, 232, 109, 233,
  203, 213, 254, 59, 0, 29, 57, 242, 239, 183, 14, 102, 88, 208, 228,
  166, 119, 114, 248, 235, 117, 75, 10, 49, 68, 80, 180, 143, 237,
  31, 26, 219, 153, 141, 51, 159, 17, 131, 20]


PADDING = ["".join(map(chr, [i]*i))  for i in range(17)]
SIZE = 16

#----------------------------------------------------------
def md2(m):

   ## (1) prepare message

   #--- append to m i byte with value i, len(m) % 16 == 0
   padLen = SIZE - len(m) % SIZE
   m += PADDING[padLen]

   #--- compute checksum C of m and append it to m
   C = [0] * SIZE
   L = 0
   for i in range(len(m) / SIZE):
      m16 = m[i*SIZE : (i+1)*SIZE]
      for j in range(SIZE):
         c = ord(m16[j])
         C[j] = PI_SUBST[ c ^ L ]
         L = C[j]
   C = "".join( map(chr, C) )
   m += C

   ## (2) compress message

   X = [0] * 48   # 'compressor'

   for i in range(len(m) / SIZE):

      # fill X
      m16 = m[i*SIZE : (i+1)*SIZE]
      X[16:32] = map(ord, m16)
      X[32:48] = [ a^b for (a,b) in zip(X[16:48], X[:16]) ]

      # compress m
      t = 0
      for j in range(18):
         for k in range(48):
            t = X[k] ^ PI_SUBST[t]
            X[k] = t
         t = (t+j) % 256

   X = "".join(map(lambda d: "%02x" % d, X[:SIZE]))
   return X


def test():
   for (i, j) in md2_test:
      md = md2(i)
      print "Message: %s" % i
      print "My   MD:%s" %  md
      print "Test MD:%s" %  j
      print "%s" % (md== j)
      print
      
if __name__ == "__main__":
   test()




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