What is the p≡p Engine?

The p≡p Engine is a Free Software library encapsulating implementations of:

• Key Management

  The p≡p Engine automatically manages keys using a pluggable crypto backend. The currently implemented backend is based on Sequoia PGP, and uses OpenPGP-format keys.

  p≡p for Email is interoperable with OpenPGP.

• Trust Rating

  The p≡p Engine sports a two phase trust rating system for messages: In phase one a rating is derived based on channel, crypto and key security. This is named "comm_types". In phase two these ratings are mapped to user-representable values mimicking the semantics of a traffic light.

• Abstract Crypto API

  The Abstract Crypto API provides functions to encrypt and decrypt data or full messages, without requiring an application programmer to understand the different applied formats and standards.

• Message Transports

  The p≡p Engine will sport a growing list of message transports, to support any widespread text-based messaging system such as E-Mail, SMS, XMPP and many more.

The p≡p Engine is written in C17 and is expected to run on any platform that conforms to the SUS/POSIX specification. Selected non-SUS platforms are supported as well (such as Microsoft Windows).

How can I use the p≡p Engine?

The entire p≡p stack including the p≡p Engine can be built with the pEp-build script https://codeberg.org/pEp/pEp-build/ on Unix machines.

(Some older build documentation, no longer supported or recommended, is also still available at https://codeberg.org/pEp/pEpEngine/wiki/adapter%3A%3Aadapter-build-instructions-version-3-x-draft )

The p≡p Engine is not meant to be used in application code directly. Instead, the p≡p Engine is meant to be used in conjunction with a so-called "adapter". An adapter provides an API in a programming language that best accomodates developers in their respective software development ecosystem. So, for example, a Java Native Interface adapter exists for development of apps for the Android mobile operating system, or a .NET adapter exists for development of applications on Microsoft Windows. Various adapters are also available at the link provided for the p≡p Engine's code above.

What is the current state of the project?

The p≡p Engine is production-ready. It is under active development by p≡p Apps. The most recent version of the source code can be obtained here: https://codeberg.org/pEp/. This is the only offical way to obtain a copy of the source code.

I would like to contribute to the p≡p Engine or a related project, where do I start?

First of all, excellent! You can find further information here: https://pep-project.org

Legal notes

The p≡p Engine is Copyright 2015-2025 by p≡p Apps, Switzerland. The source code of the p≡p Engine is licensed under the terms of the GNU General Public License version 3. Accompanying documentation is licensed under the terms of the Creative Commons Attribution-ShareAlike 3.0 Unported (CC BY-SA 3.0) License. Each file includes a notice near its beginning, that indicates the applicable license. If you wish to license the p≡p Engine under different terms, please contact us.

src/pEp_rmd160.c is adapted from LibTomCrypt by Tom St Denis and contributors, which was released by its authors into the public domain.

Contact

The p≡p team including the developers of the p≡p Engine can be reached as detailed at https://pep-project.org.