def authenticate_subscribe(message)
      subscription = PrivatePub.subscription(:channel => message["subscription"], :timestamp => message["ext"]["private_pub_timestamp"])
      if message["ext"]["private_pub_signature"] != subscription[:signature]
        message["error"] = "Incorrect signature."
      elsif PrivatePub.signature_expired? message["ext"]["private_pub_timestamp"].to_i
        message["error"] = "Signature has expired."
      end
    end
def authenticate_subscribe(message)
      subscription = PrivatePub.subscription(:channel => message["subscription"], :timestamp => message["ext"]["private_pub_timestamp"])
      if message["ext"]["private_pub_signature"] != subscription[:signature]
        message["error"] = "Incorrect signature."
      elsif PrivatePub.signature_expired? message["ext"]["private_pub_timestamp"].to_i
        message["error"] = "Signature has expired."
      end
    end
Ensure the subscription signature is correct and that it has not expired.