This library lets n parties who each have a set of k elements estimate how many disctinct elements they have without revealing the actual elements. We proposed this protocol in the paper:

Compare Before You Buy: Privacy-Preserving Selection of Threat Intelligence Providers
Jelle Vos (me), Zekeriya Erkin and Christian Doerr.

For a short overview of this work, have a look at our infographic!

You can build the project if you have cargo installed using cargo build --release.

After building, you should have a file called mpsu_ca which you can execute on a unix machine using ./mpsu_ca.

Many thanks to the authors of our dependencies. In particular, the those who developed the excellent curve25519-dalek crate that implements Curve25519 and the Ristretto encoding.