Class: HexaPDF::Encryption::RubyARC4

Inherits:
Object
  • Object
show all
Includes:
ARC4
Defined in:
lib/hexapdf/encryption/ruby_arc4.rb

Overview

Pure Ruby implementation of the general encryption algorithm ARC4.

Since this algorithm is implemented in pure Ruby, it is not very fast. Therefore the FastARC4 class based on OpenSSL should be used when possible.

For reference: This implementation is about 250 times slower than the FastARC4 version.

See: PDF2.0 s7.6.3

Instance Method Summary collapse

Methods included from ARC4

prepended

Constructor Details

#initialize(key) ⇒ RubyARC4

Creates a new ARC4 object using the given encryption key.



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# File 'lib/hexapdf/encryption/ruby_arc4.rb', line 55

def initialize(key)
  initialize_state(key)
  @i = @j = 0
end

Instance Method Details

#process(data) ⇒ Object Also known as: decrypt, encrypt

Processes the given data.

Since this is a symmetric algorithm, the same method can be used for encryption and decryption.



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# File 'lib/hexapdf/encryption/ruby_arc4.rb', line 64

def process(data)
  result = data.dup.force_encoding(Encoding::BINARY)
  di = 0
  while di < result.length
    @i = (@i + 1) % 256
    @j = (@j + @state[@i]) % 256
    @state[@i], @state[@j] = @state[@j], @state[@i]
    result.setbyte(di, result.getbyte(di) ^ @state[(@state[@i] + @state[@j]) % 256])
    di += 1
  end
  result
end