Module: DCase::Table

Includes:
Ext
Included in:
Crypto
Defined in:
lib/dcase/table.rb

Instance Method Summary collapse

Methods included from Ext

binary_path

Instance Method Details

#get_table(key) ⇒ Object 



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# File 'lib/dcase/table.rb', line 24

def get_table key
  table = Array.new(256, 0)
  decrypt_table = Array.new(256, 0)

  a = Digest::MD5.digest(key).unpack('Q<')[0]
  i = 0

  while i < 256
    table[i] = i
    i += 1
  end
  i = 1

  while i < 1024
    table = merge_sort(table, lambda { |x, y|
      a % (x + i) - a % (y + i)
    })
    i += 1
  end
  i = 0
  while i < 256
    decrypt_table[table[i]] = i
    i += 1
  end
  [ table, decrypt_table ]
end

#merge(left, right, comparison) ⇒ Object 



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# File 'lib/dcase/table.rb', line 64

def merge (left, right, comparison)
  result = []
  while (left.length > 0) and (right.length > 0)
    if comparison.call(left[0], right[0]) <= 0
      result.push left.shift()
    else
      result.push right.shift()
    end
  end
  result.push left.shift() while left.length > 0
  result.push right.shift() while right.length > 0
  result
end

#merge_sort(array, comparison) ⇒ Object 



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# File 'lib/dcase/table.rb', line 78

def merge_sort (array, comparison)
  return array if array.size < 2
  middle = (array.size / 2).ceil
  merge(merge_sort(array.slice(0, middle), comparison), merge_sort(array.slice(middle .. array.size), comparison), comparison)
end

#translate(table, buf) ⇒ Object 



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# File 'lib/dcase/table.rb', line 51

def translate(table, buf)
  table_ptr = FFI::MemoryPointer.new(:int, table.length)
  table_ptr.put_array_of_int32(0, table)

  buf_ptr = FFI::MemoryPointer.new(:string, buf.length)
  buf_ptr.put_bytes(0, buf)

  r = Ext.encrypt(table_ptr, buf_ptr, buf.length).get_bytes(0, buf.length)
  table_ptr.free
  buf_ptr.free
  r
end