class PDF::Reader::Rc4SecurityHandler
Decrypts data using the RC4 algorithim defined in the PDF
spec. Requires a decryption key, which is usually generated by PDF::Reader::StandardKeyBuilder
Public Class Methods
Source
# File lib/pdf/reader/rc4_security_handler.rb, line 15 def initialize(key) @encrypt_key = key end
Public Instance Methods
Source
# File lib/pdf/reader/rc4_security_handler.rb, line 28 def decrypt( buf, ref ) objKey = @encrypt_key.dup (0..2).each { |e| objKey << (ref.id >> e*8 & 0xFF ) } (0..1).each { |e| objKey << (ref.gen >> e*8 & 0xFF ) } length = objKey.length < 16 ? objKey.length : 16 rc4 = RC4.new( Digest::MD5.digest(objKey)[0,length] ) rc4.decrypt(buf) end
7.6.2 General Encryption Algorithm
Algorithm 1: Encryption of data using the RC4 algorithm
version <=3 or (version == 4 and CFM == V2)
buf - a string to decrypt ref - a PDF::Reader::Reference
for the object to decrypt