Where it matters.
I spoke to Dermot Turing and the other nice history guy present at a cyber networking about this the other day. They were both simultaneously horrified and confused though not disbelieving when I brought it up. They have no involvement in it I'm sure but obviously even being seen to hear these things is not good for their profile, obedience wise.
On my cryptography quasi conspiracy theory, where no cipher is secure if it's allowed to be used in public. Because the nation state will always demand a back door from the developers on pain of blocking exports of the tech otherwise. The state must have control over all communications as a first principle, they will say, is because of national security.
I'm not saying this is a good thing or bad thing. It is simply observed.
Still, this is all supposition from my own intuition. Remember how I told you about 'insight', from listening, learning about and watching Colossus running for a year - it was what was not being said that revealed the holes and delivered the insight. I do not have evidence.
In other words, the nation-state always demands the makers and developers of a new cipher give them a back door only where truly random numbers are used for perfect secrecy.
Pseudo-random numbers which are used to create a key stream in things like web browser security and pretty much everywhere else where speed is more important than perfect secrecy is where the hole is. In other words, the nation state already crack any cipher that uses a pseudo-random number(common everyday public applications )and do not need to demand a back door.
I'm ambivalent on Digital ID and CBDC etc for this very reason. They already have enough to get all they want without these. These tech propositions should be seen as yet more labour saving inventions rather than a threat to the people. The state can do you far more harm, in secret, if you disobey than having an explicit digital identity to use against you which you're aware of.
The Apple vs UK govt case last year was more 'evidence'. Apple file store must use perfect security (which would be unusual for file storage disk encryption), else there would be no need to demand a back door. Unless the UK civil service is dumb as shit, which we're certain of. Or the state is running a fear program psyop in plain sight, and it's all theatre being 'accidentally' shown to the people directly.