Class: BiCrypt

Inherits:
Object show all
Defined in:
lib/more/facets/crypt.rb

Constant Summary collapse

ULONG = 
0x100000000

Instance Method Summary collapse

Constructor Details

#initialize(userKey) ⇒ BiCrypt

Returns a new instance of BiCrypt.



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# File 'lib/more/facets/crypt.rb', line 182

def initialize(userKey)

  # These are the S-boxes given in Applied Cryptography 2nd Ed., p. 333
  @sBox = [
    [4, 10, 9, 2, 13, 8, 0, 14, 6, 11, 1, 12, 7, 15, 5, 3],
    [14, 11, 4, 12, 6, 13, 15, 10, 2, 3, 8, 1, 0, 7, 5, 9],
    [5, 8, 1, 13, 10, 3, 4, 2, 14, 15, 12, 7, 6, 0, 9, 11],
    [7, 13, 10, 1, 0, 8, 9, 15, 14, 4, 6, 12, 11, 2, 5, 3],
    [6, 12, 7, 1, 5, 15, 13, 8, 4, 10, 9, 14, 0, 3, 11, 2],
    [4, 11, 10, 0, 7, 2, 1, 13, 3, 6, 8, 5, 9, 12, 15, 14],
    [13, 11, 4, 1, 3, 15, 5, 9, 0, 10, 14, 7, 6, 8, 2, 12],
    [1, 15, 13, 0, 5, 7, 10, 4, 9, 2, 3, 14, 6, 11, 8, 12]
  ]

  # These are the S-boxes given in the GOST source code listing in Applied
  # Cryptography 2nd Ed., p. 644.  They appear to be from the DES S-boxes
  # [13,  2,  8,  4,  6, 15, 11,  1, 10,  9,  3, 14,  5,  0, 12,  7 ],
  # [ 4, 11,  2, 14, 15,  0,  8, 13,  3, 12,  9,  7,  5, 10,  6,  1 ],
  # [12,  1, 10, 15,  9,  2,  6,  8,  0, 13,  3,  4, 14,  7,  5, 11 ],
  # [ 2, 12,  4,  1,  7, 10, 11,  6,  8,  5,  3, 15, 13,  0, 14,  9 ],
  # [ 7, 13, 14,  3,  0,  6,  9, 10,  1,  2,  8,  5, 11, 12,  4, 15 ],
  # [10,  0,  9, 14,  6,  3, 15,  5,  1, 13, 12,  7, 11,  4,  2,  8 ],
  # [15,  1,  8, 14,  6, 11,  3,  4,  9,  7,  2, 13, 12,  0,  5, 10 ],
  # [14,  4, 13,  1,  2, 15, 11,  8,  3, 10,  6, 12,  5,  9,  0,  7 ]

  # precalculate the S table
  @sTable = precalculate_S_table()

  # derive the 32-byte key from the user-supplied key
  userKeyLength = userKey.length
  @key = userKey[0..31].unpack('C'*32)
  if (userKeyLength < 32)
    userKeyLength.upto(31) { @key << 0 }
  end
end

Instance Method Details

#block_size ⇒ Object 



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# File 'lib/more/facets/crypt.rb', line 178

def block_size
  return(8)
end

#carefully_open_file(filename, mode) ⇒ Object 



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# File 'lib/more/facets/crypt.rb', line 362

def carefully_open_file(filename, mode)
  begin
    aFile = File.new(filename, mode)
  rescue
    puts "Sorry. There was a problem opening the file <#{filename}>."
    aFile.close() unless aFile.nil?
    raise
  end
  return(aFile)
end

#decrypt_block(block) ⇒ Object 



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# File 'lib/more/facets/crypt.rb', line 292

def decrypt_block(block)
  xl, xr = block.unpack('NN')
  xl, xr = decrypt_pair(xl, xr)
  decrypted = [xl, xr].pack('NN')
  return(decrypted)
end

#decrypt_file(cryptFilename, plainFilename) ⇒ Object 



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# File 'lib/more/facets/crypt.rb', line 383

def decrypt_file(cryptFilename, plainFilename)
  cryptFile = carefully_open_file(cryptFilename, 'rb')
  plainFile = carefully_open_file(plainFilename, 'wb+')
  decrypt_stream(cryptFile, plainFile)
  cryptFile.close unless cryptFile.closed?
  plainFile.close unless plainFile.closed?
end

#decrypt_pair(xl, xr) ⇒ Object 



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# File 'lib/more/facets/crypt.rb', line 262

def decrypt_pair(xl, xr)
  xr ^= f(xl+@key[0])
  xl ^= f(xr+@key[1])
  xr ^= f(xl+@key[2])
  xl ^= f(xr+@key[3])
  xr ^= f(xl+@key[4])
  xl ^= f(xr+@key[5])
  xr ^= f(xl+@key[6])
  xl ^= f(xr+@key[7])
  3.times {
    xr ^= f(xl+@key[7])
    xl ^= f(xr+@key[6])
    xr ^= f(xl+@key[5])
    xl ^= f(xr+@key[4])
    xr ^= f(xl+@key[3])
    xl ^= f(xr+@key[2])
    xr ^= f(xl+@key[1])
    xl ^= f(xr+@key[0])
  }
  return([xr, xl])
end

#decrypt_stream(cryptStream, plainStream) ⇒ Object 



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# File 'lib/more/facets/crypt.rb', line 344

def decrypt_stream(cryptStream, plainStream)
  # Cypher-block-chain mode
  chain = cryptStream.read(block_size())

  while (block = cryptStream.read(block_size()))
    decrypted = decrypt_block(block)
    plainText = decrypted ^ chain
    plainStream.write(plainText) unless cryptStream.eof?
    chain = block
  end

  # write the final block, omitting the padding
  buffer = plainText.split('')
  remainingMessageBytes = buffer.last.unpack('C').first
  remainingMessageBytes.times { plainStream.write(buffer.shift) }
end

#decrypt_string(cryptText) ⇒ Object 



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# File 'lib/more/facets/crypt.rb', line 401

def decrypt_string(cryptText)
  cryptStream = StringIO.new(cryptText)
  plainStream = StringIO.new('')
  decrypt_stream(cryptStream, plainStream)
  plainText = plainStream.string
  return(plainText)
end

#encrypt_block(block) ⇒ Object 



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# File 'lib/more/facets/crypt.rb', line 284

def encrypt_block(block)
  xl, xr = block.unpack('NN')
  xl, xr = encrypt_pair(xl, xr)
  encrypted = [xl, xr].pack('NN')
  return(encrypted)
end

#encrypt_file(plainFilename, cryptFilename) ⇒ Object 



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# File 'lib/more/facets/crypt.rb', line 374

def encrypt_file(plainFilename, cryptFilename)
  plainFile = carefully_open_file(plainFilename, 'rb')
  cryptFile = carefully_open_file(cryptFilename, 'wb+')
  encrypt_stream(plainFile, cryptFile)
  plainFile.close unless plainFile.closed?
  cryptFile.close unless cryptFile.closed?
end

#encrypt_pair(xl, xr) ⇒ Object 



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# File 'lib/more/facets/crypt.rb', line 239

def encrypt_pair(xl, xr)
  3.times {
    xr ^= f(xl+@key[0])
    xl ^= f(xr+@key[1])
    xr ^= f(xl+@key[2])
    xl ^= f(xr+@key[3])
    xr ^= f(xl+@key[4])
    xl ^= f(xr+@key[5])
    xr ^= f(xl+@key[6])
    xl ^= f(xr+@key[7])
  }
  xr ^= f(xl+@key[7])
  xl ^= f(xr+@key[6])
  xr ^= f(xl+@key[5])
  xl ^= f(xr+@key[4])
  xr ^= f(xl+@key[3])
  xl ^= f(xr+@key[2])
  xr ^= f(xl+@key[1])
  xl ^= f(xr+@key[0])
  return([xr, xl])
end

#encrypt_stream(plainStream, cryptStream) ⇒ Object 



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# File 'lib/more/facets/crypt.rb', line 313

def encrypt_stream(plainStream, cryptStream)
  # Cypher-block-chain mode

  initVector = generate_initialization_vector(block_size() / 4)
  chain = encrypt_block(initVector)
  cryptStream.write(chain)

  while ((block = plainStream.read(block_size())) && (block.length == block_size()))
    block = block ^ chain
    encrypted = encrypt_block(block)
    cryptStream.write(encrypted)
    chain = encrypted
  end

  # write the final block
  # At most block_size()-1 bytes can be part of the message.
  # That means the final byte can be used to store the number of meaningful
  # bytes in the final block
  block = '' if block.nil?
  buffer = block.split('')
  remainingMessageBytes = buffer.length
  # we use 7-bit characters to avoid possible strange behavior on the Mac
  remainingMessageBytes.upto(block_size()-2) { buffer << rand(128).chr }
  buffer << remainingMessageBytes.chr
  block = buffer.join('')
  block = block ^ chain
  encrypted = encrypt_block(block)
  cryptStream.write(encrypted)
end

#encrypt_string(plainText) ⇒ Object 



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# File 'lib/more/facets/crypt.rb', line 392

def encrypt_string(plainText)
  plainStream = StringIO.new(plainText)
  cryptStream = StringIO.new('')
  encrypt_stream(plainStream, cryptStream)
  cryptText = cryptStream.string
  return(cryptText)
end

#f(longWord) ⇒ Object 



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# File 'lib/more/facets/crypt.rb', line 233

def f(longWord)
  longWord = longWord % ULONG
  a, b, c, d = [longWord].pack('L').unpack('CCCC')
  return(@sTable[3][d] ^ @sTable[2][c] ^ @sTable[1][b] ^ @sTable[0][a])
end

#generate_initialization_vector(words) ⇒ Object

When this module is mixed in with an encryption class, the class must provide three methods: encrypt_block(block) and decrypt_block(block) and block_size()



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# File 'lib/more/facets/crypt.rb', line 303

def generate_initialization_vector(words)
  srand(Time.now.to_i)
  vector = ""
  words.times {
    vector << [rand(ULONG)].pack('N')
  }
  return(vector)
end

#precalculate_S_table ⇒ Object 



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# File 'lib/more/facets/crypt.rb', line 219

def precalculate_S_table()
  sTable = [[], [], [], []]
  0.upto(3) { |i|
    0.upto(255) { |j|
      t = @sBox[2*i][j % 16] | (@sBox[2*i+1][j/16] << 4)
      u = (8*i + 11) % 32
      v = (t << u) | (t >> (32-u))
      sTable[i][j] = (v % ULONG)
    }
  }
  return(sTable)
end