I haven’t seen an off the shelf thing. It might be possible with PKI incantations but the first that comes to mind without a third party is homomorphic encrypti

I haven’t seen an off the shelf thing. It might be possible with PKI incantations but the first that comes to mind without a third party is homomorphic encryption. Libs like MS SEAL only do limited numeric operations. Without reading the research, that seems fine. Hash each name to a number. Encrypt, then do a compare. (Lots of hand waving here). Another possible scheme are things like the Google safe browsing update/client side protocol. There you’re working against hashes only. Depending on needs it may be good enough.