Class: ToyOre::Scheme::OreScheme

Inherits:
Object
  • Object
show all
Defined in:
lib/toy_ore/scheme.rb

Instance Method Summary collapse

Constructor Details

#initialize(domain_size = 0..255) ⇒ OreScheme

Returns a new instance of OreScheme.



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# File 'lib/toy_ore/scheme.rb', line 115

def initialize(domain_size = 0..255)
  @domain_size = domain_size

  # PRF key - hash key
  @prf = (domain_size).to_a.shuffle()
  # PRP key - shuffle key
  @prp = (domain_size).to_a.shuffle()
end

Instance Method Details

#encrypt(plaintext) ⇒ Object 



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# File 'lib/toy_ore/scheme.rb', line 124

def encrypt(plaintext)
  iv = rand(@domain_size)

  # This represents all the values in the domain.
  # This is a small domain example.
  # This is 1 block, 1 byte, 8 bits, total value is 256.
  domain = (@domain_size).to_a

  # Array to hold the encrypted value of the cmp result for each value in the domain.
  encryptions = []

  domain.each do |d|
    # The offset is what ever index d (domain value) is in the shuffled PRP array.
    # If we used the plaintext value as the offset, this would give away the value of the plaintext.
    # Using the PRP, swaps the plaintext value for a random number in the PRP to store the encrypted
    # comparison result in the right ciphertext encryptions array.
    offset = @prp[d]

    # Compare the domain value to the plaintext value
    # We get -1, 0 or 1 here.
    cmp_result = ToyOre::Scheme.compare_plaintexts(d, plaintext)

    # At index offset in the encryptions array
    # set the xor'd value of (iv and value) xor'd with the cmp result
    # to the index at the offset value.

    # We store the encrypted value of the comparison result
    # in the encryptions array
    # at the index = to the offset.
    #
    # To encrypt we pass the random iv, the key is the value at the offset index in the
    # random shuffled key array.
    #
    #
    encryptions[offset] = ToyOre::Scheme.encrypt(iv, @prf[offset], cmp_result)
  end

  # The left ciphertext:
  # 1.  Stores the value of the offset.
  #
  #     The offset is the index of the encrypted comparison result,
  #     in the encryptions array.
  #
  # 2.  Stores the key that was used to encrypt the comparison result
  #     at the offset in the right ciphertext.
  #
  # The right ciphertext:
  #
  # 1.  Stores the IV used in the encryption
  # 2.  Stores an array of all encrypted comparison results.
  #
  #
  #
  OreCiphertext.new(@prp[plaintext], @prf[@prp[plaintext]], iv, encryptions)
end