Class: KeySchedule

Inherits:
Object
  • Object
show all
Defined in:
lib/des/key_schedule.rb

Constant Summary collapse

PC_1_L = 
[57, 49, 41, 33, 25, 17, 9, 1, 58, 50, 42, 34, 26, 18, 10, 2, 59, 51, 43, 35, 27, 19, 11, 3, 60, 52, 44, 36]
PC_1_R = 
[63, 55, 47, 39, 31, 23, 15, 7, 62, 54, 46, 38, 30, 22, 14, 6, 61, 53, 45, 37, 29, 21, 13, 5, 28, 20, 12, 4]
PC_2 = 
[14, 17, 11, 24, 1, 5, 3, 28, 15, 6, 21, 10, 23, 19, 12, 4, 26, 8, 16, 7, 27, 20, 13, 2, 41, 52, 31, 37, 47,
55, 30, 40, 51, 45, 33, 48, 44, 49, 39, 56, 34, 53, 46, 42, 50, 36, 29, 32]
ROTATIONS = 
[1, 1, 2, 2, 2, 2, 2, 2,
1, 2, 2, 2, 2, 2, 2, 1]

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(key) ⇒ KeySchedule

Returns a new instance of KeySchedule.



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# File 'lib/des/key_schedule.rb', line 13

def initialize(key)
  @key = key

  # c[0] is the PC_1_L permutation of the key, c[1..16] are the results of each left shift.
  c = []
  # d[0] is the PC_1_R permutation of the key, d[1..16] are the results of each left shift.
  d = []
  # k[0..15] are the sub keys created by combining c[i] and d[i] and permuting with PC_2.
  k = []

  c << PC_1_L.collect { |p| key[p - 1] }
  d << PC_1_R.collect { |p| key[p - 1] }

  16.times do |i|
    c << c[i]
    d << d[i]

    ROTATIONS[i].times do
      c[i + 1] << c[i + 1].shift
      d[i + 1] << d[i + 1].shift
    end

    k << PC_2.collect { |p| (c[i + 1] + d[i + 1])[p - 1] }
  end

  @sub_keys = k
end

Instance Attribute Details

#key ⇒ Object (readonly)

Returns the value of attribute key.



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# File 'lib/des/key_schedule.rb', line 3

def key
  @key
end

#sub_keys ⇒ Object

Returns the value of attribute sub_keys.



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# File 'lib/des/key_schedule.rb', line 2

def sub_keys
  @sub_keys
end