Recently, The Washington Post published an editorial suggesting that Apple, Google, and other smart phone manufacturers provide a golden key to allow law enforcement access to locked phones. “Golden Key,” of course, is just a euphemism for a backdoor. It's unlikely that any Irreal reader will fail to understand the implications of that but here's some ammunition for talking to Aunt Millie.
Chris Coyne has an excellent post that details the problem with this proposal. As he says, increasingly our phones store our digital lives and in the near future will be a transcript of our lives, even our non-digital lives. Coyne's major point is that once there's a backdoor, others will find and use it. That could be foreign powers, rogue government agents, or criminals.
Corey Doctorow makes the same point in The Guardian and says that we can be sure that corrupt public officials will sell us out just as they have before:
“The same forces that led to bent cops selling out the public’s personal information to Glen Mulcaire and the tabloid press will cause those cops’ successors to sell out access to the world’s computer systems, too, only the numbers of people who are interested in these keys to the (United) Kingdom will be much larger, and they’ll have more money, and they’ll be able to do more damage.”
This is the same point I made in a recent post: law enforcement will always abuse any surveillance power they're given. The only way to protect ourselves is to not give them those powers.
Law enforcement, of course, claims that if they can't break into our phones they will no longer be able to investigate pedophiles, kidnappers, terrorists, and drug dealers. Bruce Schneier puts the lie to that nonsense. He recounts several instances where law enforcement has made these claims and were later found to be lying and notes that of the 3,576 warrants issued for communication intercepts in 2013, exactly one involved kidnapping. He also notes that far from “going dark,” this is the golden age of surveillance for law enforcement. Schneier's post has lots of links to more background material and you should definitely read it.