class PDF::Reader::AesV2SecurityHandler
Decrypts data using the AESV2 algorithim defined in the PDF
spec. Requires a decryption key, which is usually generated by PDF::Reader::StandardKeyBuilder
Public Class Methods
new(key)
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# File lib/pdf/reader/aes_v2_security_handler.rb, line 14 def initialize(key) @encrypt_key = key end
Public Instance Methods
decrypt( buf, ref )
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7.6.2 General Encryption Algorithm
Algorithm 1: Encryption of data using the AES-128-CBC algorithm
version == 4 and CFM == AESV2
buf - a string to decrypt ref - a PDF::Reader::Reference
for the object to decrypt
# File lib/pdf/reader/aes_v2_security_handler.rb, line 27 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 ) } objKey << 'sAlT' # Algorithm 1, b) length = objKey.length < 16 ? objKey.length : 16 cipher = OpenSSL::Cipher.new("AES-#{length << 3}-CBC") cipher.decrypt cipher.key = Digest::MD5.digest(objKey)[0,length] cipher.iv = buf[0..15] cipher.update(buf[16..-1]) + cipher.final end