Arcfour

    # File lib/prawn/arcfour.rb, line 12
12:   def initialize(key)
13:     # Convert string key to Array of integers
14:     key = key.unpack('c*') if key.is_a?(String)
15: 
16:     # 1. Allocate an 256 element array of 8 bit bytes to be used as an S-box
17:     # 2. Initialize the S-box.  Fill each entry first with it's index
18:     @sbox = (0..255).to_a
19:     
20:     # 3. Fill another array of the same size (256) with the key, repeating
21:     #    bytes as necessary.
22:     s2 = []
23:     while s2.length < 256
24:       s2 += key
25:     end
26:     s2 = s2[0, 256]
27: 
28:     # 4. Set j to zero and initialize the S-box
29:     j = 0
30:     (0..255).each do |i|
31:       j = (j + @sbox[i] + s2[i]) % 256
32:       @sbox[i], @sbox[j] = @sbox[j], @sbox[i]
33:     end
34: 
35:     @i = @j = 0
36:   end

    # File lib/prawn/arcfour.rb, line 38
38:   def encrypt(string)
39:     string.unpack('c*').map{|byte| byte ^ key_byte}.pack('c*')
40:   end

    # File lib/prawn/arcfour.rb, line 45
45:   def key_byte
46:     @i = (@i + 1) % 256
47:     @j = (@j + @sbox[@i]) % 256
48:     @sbox[@i], @sbox[@j] = @sbox[@j], @sbox[@i]
49:     @sbox[(@sbox[@i] + @sbox[@j]) % 256]
50:   end