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Non-forgeable turf/thread IDs: What can we assume re their size and properties?
In the security talk (circa slide 19, around 21 minutes in), a turf ID is shown as one field in a region descriptor. Turf IDs are also said to be non-forgeable, though how that’s achieved isn’t stated. If region descriptors must fit into the PLBs, the PLBs must either support variable sized descriptors (hard to do, while keeping the H/W fast and cheap) or must be fixed size.
If region descriptors are of fixed size and are constrained to be a single cache line each (true, or have I over-assumed?), then turf IDs are de-facto constrained in their length by the size of a cache line (on that Mill model), less the bits needed for the lower bound, upper bound and rights. If so, what is the minimum width (#bits) guaranteed for the turfID?
In general, short keys/hashes are less secure against attack, and a key length sufficient to be non-forgeable today is unlikely to remain so for very long. Are Mill turfIDs/ThreadIDs made non-forgeable via hash functions (as are the payloads in NaRs), or is there a different mechanism used to make turf (and thread) IDs unforgeable? What may we assume about the (minimum guaranteed) length and security properties of turf and thread IDs?