Class: Zwiebel::Shake256

Inherits:
Object
  • Object
show all
Defined in:
lib/zwiebel/shake256.rb

Constant Summary collapse

HEX_CHARS = 
'0123456789abcdef'.freeze
PADDING = 
[31, 7936, 2031616, 520093696].freeze
SHIFT = 
[0, 8, 16, 24].freeze
RC = 
[
  1, 0, 32898, 0, 32906, 2147483648, 2147516416, 2147483648, 32907, 0, 2147483649,
  0, 2147516545, 2147483648, 32777, 2147483648, 138, 0, 136, 0, 2147516425, 0,
  2147483658, 0, 2147516555, 0, 139, 2147483648, 32905, 2147483648, 32771,
  2147483648, 32770, 2147483648, 128, 2147483648, 32778, 0, 2147483658, 2147483648,
  2147516545, 2147483648, 32896, 2147483648, 2147483649, 0, 2147516424, 2147483648
].freeze

Instance Method Summary collapse

Constructor Details

#initialize(bit_length:, message_type: "string") ⇒ Shake256

Returns a new instance of Shake256.



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# File 'lib/zwiebel/shake256.rb', line 29

def initialize(bit_length:, message_type: "string")
  @bit_length = bit_length
  @message_type = message_type
  @finalized = false
  @reset = true
  @block = 0
  @start = 0
  @block_count = (1600 - (256 << 1)) >> 5
  @byte_count = @block_count << 2
  @output_blocks = @bit_length >> 5
  @extra_bytes = (@bit_length & 31) >> 3
  @s = Array.new(50, 0)
  @blocks = Array.new(@block_count, 0)
end

Instance Method Details

#hexdigest(data) ⇒ Object 



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# File 'lib/zwiebel/shake256.rb', line 44

def hexdigest(data)
  return if data.nil?
  if @message_type == "string"
    data_codes = data.bytes
    length = data.length
  else
    data_codes = [data].pack("H*").bytes
    length = data_codes.length
  end

  index = 0
  i = nil
  while index < length
    if @reset
      @reset = false
      @blocks[0] = @block
      1.upto(@block_count + 1) do |x|
        @blocks[x] = 0
      end
    end
    i = @start
    while index < length && i < @byte_count
      code = data_codes[index]
      if @message_type == "string"
        if code < 0x80
          @blocks[i >> 2] |= code << SHIFT[i & 3]
          i += 1
        elsif code < 0x800
          @blocks[i >> 2] |= (0xc0 | (code >> 6)) << SHIFT[i & 3]
          i += 1
          @blocks[i >> 2] |= (0x80 | (code & 0x3f)) << SHIFT[i & 3]
          i += 1
        elsif code < 0xd800 || code >= 0xe000
          @blocks[i >> 2] |= (0xe0 | (code >> 12)) << SHIFT[i & 3]
          i += 1
          @blocks[i >> 2] |= (0x80 | ((code >> 6) & 0x3f)) << SHIFT[i & 3]
          i += 1
          @blocks[i >> 2] |= (0x80 | (code & 0x3f)) << SHIFT[i & 3]
          i += 1
        else
          code = 0x10000 + (((code & 0x3ff) << 10) | (data_codes[index += 1] & 0x3ff))
          @blocks[i >> 2] |= (0xf0 | (code >> 18)) << SHIFT[i & 3]
          i += 1
          @blocks[i >> 2] |= (0x80 | ((code >> 12) & 0x3f)) << SHIFT[i & 3]
          i += 1
          @blocks[i >> 2] |= (0x80 | ((code >> 6) & 0x3f)) << SHIFT[i & 3]
          i += 1
          @blocks[i >> 2] |= (0x80 | (code & 0x3f)) << SHIFT[i & 3]
          i += 1
        end
      else
        @blocks[i >> 2] |= code << SHIFT[i & 3]
        i += 1
      end
      index += 1
    end

    @last_byte_index = i

    if i >= @byte_count
      @start = i - @byte_count
      @block = @blocks[@block_count]
      0.upto(@block_count - 1) do |x|
        @s[x] ^= @blocks[x]
      end
      keccak(@s)
      @reset = true
    else
      @start = i
    end
  end

  finalize

  hex = ""
  i = 0
  j = 0
  s = @s
  block = nil
  while j < @output_blocks
    while i < @block_count && j < @output_blocks
      block = s[i]
      hex += HEX_CHARS[(block >> 4) & 0x0F] + HEX_CHARS[block & 0x0F] +
        HEX_CHARS[(block >> 12) & 0x0F] + HEX_CHARS[(block >> 8) & 0x0F] +
        HEX_CHARS[(block >> 20) & 0x0F] + HEX_CHARS[(block >> 16) & 0x0F] +
        HEX_CHARS[(block >> 28) & 0x0F] + HEX_CHARS[(block >> 24) & 0x0F]
      j += 1
      i += 1
    end

    if j % @block_count == 0
      s = s.dup
      keccak(s)
      i = 0
    end
  end

  if @extra_bytes > 0
    block = s[i]
    hex += HEX_CHARS[(block >> 4) & 0x0F] + HEX_CHARS[block & 0x0F]
    if @extra_bytes > 1
      hex += HEX_CHARS[(block >> 12) & 0x0F] + HEX_CHARS[(block >> 8) & 0x0F]
    end
    if @extra_bytes > 2
      hex += HEX_CHARS[(block >> 20) & 0x0F] + HEX_CHARS[(block >> 16) & 0x0F]
    end
  end

  hex
end