Method: Crypt::Gost#initialize

Defined in:
lib/extensions/crypt/crypt/gost.rb

#initialize(userKey) ⇒ Gost

Returns a new instance of Gost.



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# File 'lib/extensions/crypt/crypt/gost.rb', line 19

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