>Allo messages will still be encrypted between the device and Google servers, and stored on servers using encryption that leaves the messages accessible to Google’s algorithms. 'using encryption that leaves the messages accessible to Google’s algorithms' So, not meaningfully encrypted at all then?
They could be using some form of homomorphic encryption here, in which case it would still be meaningfully encrypted.
So, in order to perform machine learning on terabytes of data, you need to flip terabits for every update of the homomorphic state machine.
That being said, I could imagine someone coming up with a homomorphic encryption algorithm that starts out with a few megabits of excess entropy and leaks entropy at a bounded rate while remaining more efficient at calculation, and where the initial state is set up cleverly such that after a bounded number of steps, the state machine starts making nonsense computations and stops leaking entropy. Though, this just feels very brittle to intentionally leak entropy, and I have no idea how anything remotely like this could be actually constructed.