#!/usr/bin/python

sig="""
-----BEGIN PGP SIGNED MESSAGE-----

# This program implements a hash function based entirely on modular
# exponentiation which was proposed by Adi Shamir. A prove of
# collision-resistance was presented by Ronald L. Rivest.
# (see: http://senderek.de/SDLH for details)
#
# The code was written by Ralf Senderek (27/7/2003)
# This  is  free software.
# Use this software on your own risk or not at all.
# There is NO warranty; not even for MERCHANTABILITY
# or FITNESS FOR A PARTICULAR PURPOSE.
"""
import sys

HashModulus = 127591803097286953893100494339441011348391052328504594272155043892693303336312481545545475054278478854524034312374432499270105554744411485832351021152505745773538402718187183756998476794675330042232393745790032655631295437331043707963163673832402724061250274903083004931263395006053506534674232415216812527609L
Min_Hashmodulus = 1024
HashModulusLength = 1024
Prime1 = 102639592829741105772054196573991675900716567808038066803341933521790711307779L
Prime2 = 106603488380168454820927220360012878679207958575989291522270608237193062808643L
# Both primes were taken from the RSA-155 factoring challenge Aug. 1999
Generator = Prime1 * Prime2        # 512 Bits
GeneratorLength = 512

################################################################

def ModExp (Base, Exp, Mod):

     Hash = 1

     X = Exp
     Factor = Base

     while X > 0 :
          Remainder = X % 2
          X = X / 2
          if Remainder == 1:
               Hash = Hash * Factor % Mod
          Factor = Factor * Factor %  Mod
     return Hash

################################################################

def slow_SDLH(Message) :

     Number = 0L
     index = 0
     while index < len(Message) :
          Number = Number * 256 + ord(Message[index])
          index = index + 1

     return ModExp(Generator, Number, HashModulus)

################################################################

def SDLH(Message) :

     # Calculates    hash(x) = Generator^x mod HashModulus
     #
     # Speeding up the computation by avoiding to convert the string into
     # a long integer
     # This code processes characters one by one using
     # two ModExp()-operations for every character

     # Hash = 1
     # for Character in Message:
     #  (1)    A = ModExp(Generator, ord(Character), HashModulus)
     #  (2)    B = ModExp(Hash, 256, HashModulus)
     #  (3)    Hash = (A * B) % HashModulus
     # return  Hash

     # Implementation with precomputed table

     # precomputing table for step (1)
     table = []
     table.append(1L)
     index = 1
     Number = 1L
     while index < 256 :
          Number = (Number * Generator) % HashModulus
          table.append(Number)
          index = index + 1

     # process the message character by character
     Hash = 1
     for Character in Message:
          A = table[ord(Character)]      # step (1)

          B = Hash                       # step (2)
          index = 8
          while index > 0 :
               B = (B * B)  % HashModulus
               index = index - 1

          Hash = (A * B) % HashModulus   # step (3)

     return  Hash

################################################################

def SDLH256(Message) :

     Hash256 = 0L
     X = SDLH(Message)
     Size = pow(2,256L)
     while X > 0 :
          Section = X % Size
          X = X / Size
          Hash256 = Hash256 ^ Section    # XOR operation
     return Hash256

################################################################

def read_keyfile(FileName) :
     import string
     global HashModulus, HashModulusLength, Generator, GeneratorLength
     global UserID

     try:
          FILE = open(FileName, "r")
          Key = FILE.readlines()
          FILE.close()
     except :
          print "Cannot open keyfile ", FileName
          sys.exit(2)

     if len(Key) >= 3 :
          try:
               if string.upper(Key[0][:11]) == "HASHMODULUS" and string.upper(Key[1][:9]) == "GENERATOR" :
                    HashModulus = long(Key[0][14:-1])
                    X = HashModulus
                    HashModulusLength = 0
                    while X > 0 :
                         X = X / 2
                         HashModulusLength = HashModulusLength + 1
                    Generator = long(Key[1][12:-1])
                    GeneratorLength = 0
                    X = Generator
                    while X > 0 :
                         X = X / 2
                         GeneratorLength = GeneratorLength + 1
                    if HashModulusLength < Min_Hashmodulus :
                         print "The Hashmodulus is too short!"
                         sys.exit(2)
                    if 2*GeneratorLength < Min_Hashmodulus :
                         print "The Generator is too short!"
                         sys.exit(2)
               else :
                    error()
               UserID = Key[2][:-1] + " (" + str(HashModulusLength) + "," + str(GeneratorLength) + ")"
          except:
               print "The neccessary key information is not available."
               sys.exit(2)
     else:
          error()
          sys.exit(2)

################################################################

def print_hash(Message, Filename) :

     if Bits == 256 :
          Hash = SDLH256(Text)
     else :
          if Mode == "fast" :
               Hash = SDLH(Text)
          else :
               Hash = slow_SDLH(Text)

     print Hash, Filename,
     print Bits, "bit"
     print


################################################################

def error() :
    print "The keyfile is corrupt.",
    print "It must consist of 3 lines (for example)."
    print ""
    print "Hashmodulus = 342345"
    print "Generator = 323471"
    print "User Identification String"
    print ""
    sys.exit(2)

################################################################
#   MAIN                                                       #
################################################################

Bits = HashModulusLength
Mode = "fast"
Key = "default"
UserID = "None"
HOME = "."

# look for a config file with hashkey information.
import os

if os.name == "posix":
     HOME = os.environ['HOME']
if os.path.exists(HOME + "/.hashkey") :
     read_keyfile(HOME + "/.hashkey")
     Key = "config"
else:
     print "No config file found."

if len(sys.argv) > 0 :
     if len(sys.argv) > 1 :
          if sys.argv[1] == "-256" :
               Bits = 256
               del sys.argv[1]
          if (len(sys.argv) > 1) and (sys.argv[1] == "-slow") :
               print "Slow hashing ..."
               Mode = "slow"
               del sys.argv[1]
          if (len(sys.argv) > 1 ) and (sys.argv[1] == "-key") and (len(sys.argv) >= 3) :
               read_keyfile(sys.argv[2])
               Key = "file"
               del sys.argv[1:3]

     if Bits != 256 :
           Bits = HashModulusLength
     if Key == "config":
           print "Using config file."
     if Key == "file":
           print "Using key file."
     if Key == "default":
           print "Using default values."
     print "User: ", UserID

     if (len(sys.argv) == 1) or (sys.argv[1] == "-"):
          F = sys.stdin
          Text = F.read()
          F.close()
          print_hash(Text, "stdin")
          sys.exit(0)
     else :
          for File in sys.argv[1:] :
               try:
                     F = open(File , "r")
                     Text = F.read()
                     F.close()
                     print_hash(Text, File)
               except:
                     print "Cannot open file ", File

else :
     print "usage: sdlh [-256] [-slow] [-key keyfile] file"

sys.exit(0)

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