What's interesting is that approach (software-defined 'random' numbers to associate memory regions and valid pointers) provides only probabilistic memory safety. A malicious actor may find a way to spoof/guess the tag needed to access a particular piece of memory. Given Arm MTE has been breached in the last year, it's hard to argue that it's a good enough security guarantee. EMTE may fix issues (e.g. side-channels) but leaves open the probabilistic pathway (i.e. "guess the tag") which is a hole MTE isn't designed to try to close (so, a software breach on top of a chip with EMTE can't necessarily be argued to be a violation of the hardware's security properties, though it may exploit the architectural security hole).

In contrast, CHERI and OMA (Object Memory Architecture) are both providing hardware-enforced guarantees of memory safety properties - unbreakable even if the attacker has perfect knowledge - backed up by formal proofs of these claims.

CHERI offers referential and spatial safety as hardware guarantees, with temporal being achievable in software. OMA offers referential, spatial and temporal safety as hardware guarantees.