diff --git a/book/source/02-highlevel.md b/book/source/02-highlevel.md
index f6cb52c..ada30ae 100644
--- a/book/source/02-highlevel.md
+++ b/book/source/02-highlevel.md
@@ -64,8 +64,9 @@ Some implementations explored other non-standardized extensions. Notably, algori
 
 Today, multiple implementations of OpenPGP play important roles:
 
-- Proton Mail, which provides email encryption services for a large number of users, uses and maintains [OpenPGP.js](https://openpgpjs.org/) as well as [GopenPGP](https://gopenpgp.org/), an OpenPGP wrapper library written in golang.
 - The Mozilla Thunderbird email software uses [RNP](https://www.rnpgp.org/), a C++ implementation of OpenPGP.
+- [GNU Privacy Guard (GnuPG)](https://gnupg.org/), a key implementation of the OpenPGP standard, is integral to numerous critical infrastructures, most prominently in ensuring package integrity verification for Linux distributions.
+- Proton Mail, which provides email encryption services for a large number of users, uses and maintains [OpenPGP.js](https://openpgpjs.org/) as well as [GopenPGP](https://gopenpgp.org/), an OpenPGP wrapper library written in golang.
 - The RPM Package Manager software includes an OpenPGP backend based on [Sequoia PGP](https://sequoia-pgp.org/), a modern OpenPGP implementation written in Rust. The Fedora Linux operating system [uses Sequoia PGP in rpm](https://sequoia-pgp.org/blog/2023/04/27/rpm-sequoia/) since version 38.
 
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