class PDF::Reader::SecurityHandlerFactory

def self.standard_v5?(encrypt)
  return false if encrypt.nil?
  filter = encrypt.fetch(:Filter, :Standard)
  version = encrypt.fetch(:V, 0)
  revision = encrypt.fetch(:R, 0)
  algorithm = encrypt.fetch(:CF, {}).fetch(encrypt[:StmF], {}).fetch(:CFM, nil)
  (filter == :Standard) && (encrypt[:StmF] == encrypt[:StrF]) &&
      ((version == 5) && (revision == 5 || revision == 6) && (algorithm == :AESV3))
end