✨ Adds sid to KeyAccess objects

[dmihalcik-virtru]

Proposed Changes

• This allows both copies and spits for keys.
• Adds a section on how they are to be used, with samples

Checklist

• A clear description of the change has been included in this PR.
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[strantalis]

@dmihalcik-virtru Is this the right way to think about this.

No Split ID

Same DEK is shared and not split

Same Split IDs

DEK is XOR'd

Group'd Split IDs

DEK is XOR'd once per group of split ids.

So you could have group kas working in group a but you might need to use local.hsm in group b?

[dmihalcik-virtru]

yes. A weakness of the proposed approach is you have to have there is the same split for different sets of KASes you want to share them with. Thus the 'hybrid' example still has to do two rewraps and an xor for accessing the DEK via the local server, even though that provides no additional security.