This can be considered a follow up to Do randomized PIDs bring more security?
A major problem with random PIDs is that they repeat more quickly than sequential PIDs, but in cryptography, we can permute sequential PIDs with a secret key in such way that no one can predict it, essentially making it appear random - in an actual OS kernel, this key would be under system protection.
Next, for initial ~100 PIDs that're have reserved meanings (e.g. 1 for init and a few others for system processes), we can just reject a PID if it fall in that range - this is as if a process with that PID started, died, and then reborn with a different PID.
Q: is this idea adopted anywhere? are there other downsides of random PIDs not solved by generating them deterministically?