As the International Principles on the Application of Human Rights to Communications Surveillance make clear, the preservation of the integrity of communications and systems is a key obligation under international law. Just as it would be unreasonable for governments to insist that all residents of houses should leave their doors unlocked just in case the police need to search a particular property, or to require all persons to install surveillance cameras in their houses on the basis that it might be useful to future prosecutions, it is equally disproportionate for governments to interfere with the integrity of everyone’s communications in order to facilitate its investigations or to require the identification of users as a precondition for service provision or the retention of all customer data. …