Class: ExtID::Type

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

Instance Method Summary collapse

Constructor Details

#initialize(prefix, key) ⇒ Type

Returns a new instance of Type.

Raises:

  • (ArgumentError) 


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# File 'lib/extid.rb', line 11

def initialize(prefix, key)
  raise ArgumentError, "key must be exactly 16 bytes" unless key.bytesize == 16

  @prefix = prefix + "_"
  @key = key
end

Instance Method Details

#decode(s) ⇒ Object

Raises:

  • (ArgumentError) 


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# File 'lib/extid.rb', line 35

def decode(s)
  raise ArgumentError, "invalid prefix" unless s.start_with?(@prefix)
  hex_ciphertext = s[@prefix.size..]
  ciphertext = [hex_ciphertext].pack("H*")

  cipher = OpenSSL::Cipher.new('AES-128-ECB')
  cipher.decrypt
  cipher.key = @key
  cipher.padding = 0

  plaintext = cipher.update(ciphertext) + cipher.final
  plaintext[0, 8].unpack("q>").first
end

#encode(n) ⇒ Object

Raises:

  • (ArgumentError) 


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# File 'lib/extid.rb', line 18

def encode(n)
  raise ArgumentError, "n is too small" unless n >= MinInt64
  raise ArgumentError, "n is too big" unless n <= MaxInt64

  binary_number = [n].pack("q>")
  raise ArgumentError, "n could not be encoded into 64-bit binary" unless binary_number.bytesize == 8
  plaintext = binary_number + "\x0\x0\x0\x0\x0\x0\x0\x0"

  cipher = OpenSSL::Cipher.new('AES-128-ECB')
  cipher.encrypt
  cipher.key = @key
  cipher.padding = 0

  ciphertext = cipher.update(plaintext) + cipher.final
  @prefix + ciphertext.unpack("H*").first
end