An extended version of this piece was originally published December, 2015, on the Association for Computing Machinery's Huffington Post blog. It has been excerpted and updated slightly here to speak to the recent news around Apple and the FBI's request for backdoor access.
We are not here to debate whether such access is useful from a policy perspective, i.e. whether it would work to stop bad guys. While a critical conversation that raises many questions, we leave that to others. We are here to review the technical realities, and to explore the impact and potential danger of such proposals from this perspective.
The ability to secure Internet technologies — to ensure that the right people gain access to the right things, and the wrong people don't — is what makes online banking and commerce possible, and is what allowed the Internet to become an unprecedented driver of economic and social change. This point is not up for debate. What we now need to understand is that the call to provide law enforcement (or anyone) exceptional access to communications and content poses a grave threat to the sustainability and future of the Internet: it is simply not possible to give the good guys the access they want without letting the bad guys in. There's nothing new or novel in this statement. Experts have been saying the same thing for 20 years. But while the message is old, with the integration of Internet technologies into nearly all aspects of life, the stakes are higher than they've ever been.
Machines don't know a bad guy from a good guy. Machines respond as they've been programmed to respond. Programming them (with new software, or otherwise) to open up to third parties cannot be guaranteed to limit access to only those intended: it limits access to anyone who is able to make a request in a way that the machine responds to. In the case of Apple, the FBI is requesting new software that would enable them to crack an iPhone user's password and bypass the security measures in place to prevent such intrusion. Were Apple to build such software, it would create a "backdoor" into one criminal's iPhone, and any other iPhone model with which the software requested can be used. Apple is being asked to give the FBI — and anyone else who obtains the software in question — a ticket to exceptional access.
The risks are not theoretical: we know of no case where adding extraordinary access capabilities to a system has not resulted in weakened security.
Take the case of the Communications Assistance for Law Enforcement Act (CALEA), a 1994 law designed to make it easier for US law enforcement to tap phone conversations. Under this law, telephone companies had to design their systems to allow wiretapping — adding a vector for extraordinary access (similar in kind to what's being requested of Apple). It was due to CALEA-mandated wiretapping capabilities that, in 2012 all of the Department of Defense's phone switches were reported to be vulnerable. Similar capabilities, built to comply with CALEA-like laws, were exploited to eavesdrop on the phone conversations of Greece's Prime Minister and those of at least 100 other dignitaries and politicians, some of them US diplomats. It was these same mechanisms that were used to illegally tap phone conversations of at least 5000 people in Italy. In the Greek case, it's unclear who did it. In the Italian case, the crime appears to have been authorized by a high-ranking official at the Italian SISMI military intelligence agency. From our perspective it doesn't matter — if the means for extraordinary access weren't there, these crimes almost certainly wouldn't have happened.