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divviup / janus

Experimental implementation of the Distributed Aggregation Protocol (DAP) specification.
Mozilla Public License 2.0
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`janus_client` should have preferences for HPKE configurations #857

Closed tgeoghegan closed 1 year ago

tgeoghegan commented 1 year ago

As of DAP-03, aggregators may advertise multiple HPKE configurations for a given task. janus_client needs to decide what HPKE config to use when presented with a list. I think by default, we could choose whichever one we think is fastest (though that will vary based on e.g. whether AES is accelerated on the platform), but we might want to allow clients to configure allow- or deny-lists. For example, some clients might only allow NIST cryptography and thus will want to stick to P-256 and AES.

divergentdave commented 1 year ago

In particular, we need to add the rest of the HPKE KEM codepoints to our HpkeKemId enumeration, and then discard keys we don't support (P-384, P-521, and X448) when filtering through a HpkeConfigList.