Implementation of the “ARCFOUR” algorithm (“alleged RC4 (tm)”). Implemented as described at: www.mozilla.org/projects/security/pki/nss/draft-kaukonen-cipher-arcfour-03.txt
“RC4” is a trademark of RSA Data Security, Inc.
Copyright August 2009, Brad Ediger. All Rights Reserved.
This is free software. Please see the LICENSE and COPYING files for details.
# File lib/prawn/security/arcfour.rb, line 12 def initialize(key) # Convert string key to Array of integers key = key.unpack('c*') if key.is_a?(String) # 1. Allocate an 256 element array of 8 bit bytes to be used as an S-box # 2. Initialize the S-box. Fill each entry first with it's index @sbox = (0..255).to_a # 3. Fill another array of the same size (256) with the key, repeating # bytes as necessary. s2 = [] while s2.length < 256 s2 += key end s2 = s2[0, 256] # 4. Set j to zero and initialize the S-box j = 0 (0..255).each do |i| j = (j + @sbox[i] + s2[i]) % 256 @sbox[i], @sbox[j] = @sbox[j], @sbox[i] end @i = @j = 0 end
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