[imperiopolis]

Yes, that is the work "individually" is doing here – multiple realms (services) could collude to combine shards and attempt to extract secrets.

However, programmable HSMs, with verifiable software (e.g. via a key ceremony), minimize this form of collusion. The shards they hold can't be extracted by a malicious operator, at least without substantial effort (requiring HSM hardware vulnerabilities).

[themoonisachees]

Interesting. Thanks for the explanations!