Apple wants its users' secrets to be secret.
The UK wants the fact it wants Apple to reveal anyone's secrets to be secret.
Apple wants its users' secrets to be secret.
The UK wants the fact it wants Apple to reveal anyone's secrets to be secret.
The criminals per definition don't care what they use, as long as it's unbreakable, so in the event that strong encryption is outlawed, they'll just switch to illegal encryption, or any other form of secret communication.
If you implement a backdoor in iMessage, criminals will stop using that, and switch to Signal (they probably already have long before this), or setup private message services, or anything in between.
Governments falsely claim that they've always had the right to pry in your private data, but while they've always had the option (provided proper paperwork from courts) to tap your phone and read your mail, they've never been able to simply dig through everything you ever wrote at any point in time. All the so called privileges they had were reactive, going forward in time after they had proven in a court that you should be the target for investigation. If they purposely weaken encryption, they will have unrestricted access to everything you've ever said or written.
Worst case, Weakening encryption for the average user only leads to "minority report" style arrests, where you can be arrested for "thoughtcrime" for something you're written and never published, but because it's no longer a secret, "anybody" can read and interpret on it.
And maybe they are even more lazy than average people because that's why they became criminals in the first place.
I'm not too worried about your average "small scale" criminal suddenly becoming a criminal mastermind, but organized crime will certainly adopt safer ways of communicating, and those are the people you want to catch with electronic surveillance.
The small scale criminals usually leaves plenty of other clues that will allow the police to capture them.
With sufficient motivation (money is a great motivator), everything is possible, especially if not doing X will remove said money, and/or put you in jail.
It's not even like they need to fork Signal/Session, they could get by with GPG encrypting a gist and uploading that, sharing the link in signal or wherever.
As I initially wrote, weakening encryption only harms law abiding citizens, as everybody criminal probably faces much worse charges than breaking encryption laws.