"We know of no case where such an addition of exceptional access capabilities has not resulted in weakened security."
That's the key takeaway from this essential Association for Computing Machinery editorial from crypto/security researchers Meredith Whittaker and Ben Laurie, writing some incredibly sensible, blunt material about the law enforcement initiatives all over the world to mandate weaker computer security to make it easier to spy on potential terrorists.
These risks are not theoretical: we know of no case where such an addition of exceptional access capabilities has not resulted in weakened security.
Take the Communications Assistance for Law Enforcement Act (CALEA), a 1994 law intended 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 exceptional access. 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 at least 100 other dignitaries and politicians, some of them US diplomats. It was these same capabilities 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 exceptional access weren't there, these breaches almost certainly wouldn't have happened.
In addition to the technical complexities, there is an inescapable policy question: how do we determine whose law enforcement and government should be allowed to use this exceptional access and for what purpose? Who are the "good guys," and according to whom? Should the Chinese, Canadian, US, and South Sudanese governments all be granted access under the same terms? Whose agendas and policies do we favor, and what does consensus look like? How can such a large and complicated decision-making process make room for the type of innovation that made the Internet what it is? How do we audit access and make room for democratic oversight? And, finally, how do we program millions of machines to respect the huge and dynamic complexity of such decisions, assuming such a process is even possible?
Wanting It Bad Enough Won't Make It Work: Why Adding Backdoors and Weakening Encryption Threatens the Internet [Meredith Whittaker and Ben Laurie/ACM]