# Private Set Membership (PSM) | Cryptographic Protocol That Allows Clients To Privately Query

**URL:** <https://onehack.st/t/private-set-membership-psm-cryptographic-protocol-that-allows-clients-to-privately-query/206520>\
**Category:** Tools & Scripts\
**Tags:** tools\
**Created:** [November 10, 2021, 11:31am UTC](https://onehack.st/t/private-set-membership-psm-cryptographic-protocol-that-allows-clients-to-privately-query/206520 "2021-11-10T11:31:46Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![WhiteHat](https://onehack.st/user_avatar/onehack.st/whitehat/32/162514_2.png) [@WhiteHat](https://onehack.st/u/WhiteHat)\
**Post date:** [November 10, 2021, 11:31am UTC](https://onehack.st/t/private-set-membership-psm-cryptographic-protocol-that-allows-clients-to-privately-query/206520/1 "2021-11-10T11:31:46Z")

</div>

![image](https://onehack.st/uploads/default/original/3X/5/0/504052b39bfad3782e0cd2f6b0dc5e5ce697c23e.jpeg)

# Private Set Membership (PSM)

## Problem Statement

Private Set Membership (PSM) is a cryptographic protocol that allows clients to privately query whether the client’s identifier is a member of a set of identifiers held by a server in a privacy-preserving manner.

At a high level, PSM provides the following privacy guarantees:

- The server does not learn the client’s queried identifier in the plaintext.
- The server does not learn whether the client’s query results in a membership or non-membership determination.
- The querying client does not learn any information about the set of identifiers that are stored by the server beyond whether the querying client’s identifier is a member or not of the server-held set of identifiers. In other words, the querying client learns the bare minimum amount of information which is only the answer of the membership query.

## Dependencies

The Private Set Membership library requires the following dependencies:

- [Abseil](https://github.com/abseil/abseil-cpp) for C++ common libraries.
- [Bazel](https://github.com/bazelbuild/bazel) for building the library.
- [BoringSSL](https://github.com/google/boringssl) for underlying cryptographic operations.
- [GFlag](https://github.com/gflags/gflags) for flags. Needed to use glog.
- [GLog](https://github.com/google/glog) for logging.
- [Google Test](https://github.com/google/googletest) for unit testing the library.
- [Protocol Buffers](https://github.com/google/protobuf) for data serialization.
- [Shell](https://github.com/google/shell-encryption) for fully homomorphic encryption.
- [Tink](https://github.com/google/tink) for cryptographic PRNGs.

## How to build

In order to run this library, you need to install Bazel, if you don’t have it already. [Follow the instructions for your platform on the Bazel website. Make sure you are installing version 4.2.1 or above.] ([https://docs.bazel.build/versions/master/install.html](https://docs.bazel.build/versions/master/install.html))

You also need to install Git, if you don’t have it already. [Follow the instructions for your platform on the Git website.](https://git-scm.com/book/en/v2/Getting-Started-Installing-Git)

Once you’ve installed Bazel and Git, open a Terminal and clone the repository into a local folder.

Navigate into the `private-membership` folder you just created, and build the library and dependencies using Bazel. Note, the library must be built using C++17.

cd private-membership bazel build … --cxxopt=‘-std=c++17’

You may also run all tests (recursively) using the following command:

bazel test … --cxxopt=‘-std=c++17’

## Disclaimers

This is not an officially supported Google product. The software is provided as-is without any guarantees or warranties, express or implied.

## GitHub:

> **[GitHub - google/private-membership](https://github.com/google/private-membership)**
>
> Contribute to google/private-membership development by creating an account on GitHub.