What is open-source encryption? A complete guide

What is open-source encryption, and why does it matter?

Open-source encryption means the code of the application or service protecting your data is publicly available for anyone to inspect and verify, so you don't have to rely solely on a company's claims.

Learn how open-source encryption works, how it’s reviewed, and why transparency plays a key role in digital security.

What is it?What makes encryption open-source Examples How it's verified FAQ

What is open-source encryption?

Open-source encryption refers to encryption software whose source code is publicly available for anyone to view, inspect, use, modify, and share under specific licensing terms. Instead of relying solely on what a company says about its security, you can see what independent experts, researchers, and developers have to say about how the encryption actually works.

This transparency sets open-source encryption apart from proprietary (closed-source) systems, where the code is kept private. Many believe this openness helps build trust because the security can be verified rather than hidden behind secrecy.

What makes encryption open-source

Peer review

Because the open-source code is publicly available, anyone can see how the encryption works.

Security experts from different backgrounds such as industry, academia, and independent communities can review the code, run audits, and find weaknesses more quickly than in closed development models.

Licensing

Open-source encryption software must be released under a license that defines how it can be legally used.

For example, if it can be used commercially, modified, combined with proprietary systems, or whether improvements must be shared back.

Common open-source licenses include the MIT License, Apache License 2.0, BSD licenses, and GNU General Public License (GPL).

Free to use and no vendor lock-in

Many open-source encryption tools are free to use, which makes strong security more accessible to people and organizations, including startups, nonprofits, and schools.

Since the code can be changed, organizations can adjust encryption tools to fit their needs and use them with their existing systems without relying on one vendor.

Examples of open-source encryption tools

Here are some popular open-source encryption tools used for protecting data, communications, and online privacy:

GnuPG (GNU Privacy Guard) is a widely used implementation of OpenPGP encryption for encrypting files, emails, and signing software releases. It’s popular among developers, journalists, and privacy-focused users. Proton apps use OpenPGP.js(nuova finestra) and GoOpenPGP, both of which are OpenPGP implementations.
VeraCrypt is a disk encryption tool derived from the older TrueCrypt project, which allows the creation of encrypted containers or full-disk encryption. It's often used for encrypting files and protecting sensitive data on laptops or external drives.
The Signal Protocol is an end-to-end encryption protocol use din secure messaging apps such as Signal.
WireGuard®(nuova finestra) is an open-source VPN protocol designed to secure network connections. It's often used in VPN services, corporate networks, and self-hosted privacy setups. Proton VPN uses WireGuard(nuova finestra).
OpenSSL is a foundational cryptographic library used by websites, servers, and apps which powers much of the HTTPS encryption across the internet.
Tor (The Onion Router) is a network that encrypts and routes traffic through multiple nodes to help anonymize internet activity and bypass censorship. You can access all Proton apps on Tor.

How open-source encryption is verified

Security audits

Independent security specialists review open-source encryption code to look for vulnerabilities, coding mistakes, or areas that don’t follow cryptographic best practices.

For example, an encryption library used in messaging apps might be audited to confirm it handles encryption keys safely.

Community scrutiny

Since open-source code is publicly available on platforms like GitHub(nuova finestra), any vulnerabilities can be identified and discussed openly.

Active communities often contribute fixes, clearer documentation, and performance improvements over time.

Bug bounty programs

To encourage independent security testing, some organizations run public bug bounty initiatives.

These programs allow security specialists to safely look for vulnerabilities, submit findings, and receive recognition or financial rewards.

Academic and standards review

Academic researchers analyze cryptographic designs, implementations, and real-world usage of open-source encryption in published studies and security conferences.

Standards organizations such as NIST, ISO/IEC, and the IETF develop guidelines that many projects follow.

Frequently asked questions

Is open-source encryption software secure?: One of the arguments made against open-source encryption software is that it’s less secure than proprietary software because anyone can contribute to it. This, however, isn’t the case.
Besides lowered costs and increased flexibility, open-source projects are more transparent about vulnerabilities as the source code is publicly accessible. Due to its open nature, anyone in the community can detect and resolve security flaws before they pose a serious threat to the wider community.
If you're a developer, you can review the code yourself, make modifications, and even release a custom version of the software. Open-source projects allow anyone with the technical expertise to fix broken code, whereas with proprietary software, only the vendor or company can examine and update it. As a result, open-source software is often more reliable and secure than proprietary software.
Is open-source encryption software good quality?: Although open-source software is available for modification by anyone, that doesn’t mean that every modification is accepted, which could result in a low-quality tool. In fact, most open-source projects use a workflow where a lead developer or a group of developers must sign off on all changes made to the code. Many open-source projects experience the same quality assurance checks as proprietary projects do, as they undergo code review and testing and adhere to consistent guidelines(nuova finestra).
Can you get technical support for open-source encryption software?: Open-source projects are surrounded by vibrant communities of developers and volunteers with a collective interest in creating a high-quality product. The larger the community, the more likely you are to find solutions for an issue you’re facing. Most open-source projects have dedicated forums where users can post questions and troubleshoot bugs through crowdsourcing.
When a project is open source, you can also look at the version history to get an idea of the time required to resolve a bug and receive an update. In addition, many tech companies use open-source code in their projects, which is a strong vote of confidence for continued support of larger open-source ventures.
Why is open source good for encryption?: By opening up the source code, anyone can directly verify that the encryption features are implemented correctly and no backdoors are built in. You can also hire third-party security firms to conduct independent audits.
Open-source encryption enables individuals, experienced developers, and cryptography experts to learn what algorithms are employed, how they work, and point out potential flaws and vulnerabilities. This transparency makes it possible to quickly resolve bugs and independently assess the security of an application, which leads to better privacy.

Take charge of your data

Proton was built to protect your data from the start. With end-to-end encryption, open-source apps, and independent audits, your information stays yours.

Start using Proton encryption today

Find out more about Proton security and compliance in our Trust Center.