Proton Mail’s open-source encryption library, OpenPGPjs, has passed an independent security audit

Irina Marcopol

Share this page

At Proton Mail, our goal is to make encryption as widespread and accessible as possible. We believe a key step toward that is having well-maintained, robust, and secure open source encryption libraries(new window). This is the goal of our efforts on the OpenPGPjs encryption(new window) library, which is today used by hundreds of applications (including Proton Mail) serving millions around the world. As the maintainer of OpenPGPjs, we are responsible for making sure the library is up to date and secure, as well as offering basic support to developers who wish to use it.

In March 2018, we released Version 3.0 of OpenPGPjs(new window). With this major update, OpenPGPjs is even more powerful, secure, and efficient. As part of this update, the OpenPGPjs developer community commissioned an independent security audit from the well-respected security firm Cure53(new window). Independent security audits are an important way to ensure there are no vulnerabilities that could be exploited by attackers.

Summer 2018 Security Audit Coverage

The version 3.0 release brought many new features and improvements, such as support for elliptic curve cryptography(new window) (ECC), which uses smaller signing and encryption keys compared with RSA cryptography(new window) (what Proton Mail uses now), making it a faster and more efficient alternative.

The new version also adds compression, which reduces the size of data before encryption to save space (and time) during encryption and transmission. OpenPGPjs now also offers support for AEAD(new window) (Authenticated Encryption with Associated Data). This protocol provides confidentiality, integrity, and authenticity guarantees on encrypted data, so that when you decrypt data, you can be sure this was the exact same data encrypted by your sender, and you can be sure that it was indeed encrypted by that sender. For those who are interested, you can find the full technical details of OpenPGPjs Version 3.0 here(new window).

The Cure53 team focused on a couple of these new features while also taking a closer look at some key aspects of OpenPGPjs’ crypto implementations. In particular, the audit focused on the following:

  • AEAD encrypted packets
  • EAX, GCM, OCB
  • CMAC
  • All cryptographic primitive implementations: AES, AES-EAX, AES-GCM, AES-CBC, ED25519, C25519, ECDSA, HMAC, P256, P384, P521, SECP256K1
  • Prime number handling
  • Date support in signatures
  • Cryptographic API exposure via different providers

OpenPGPjs Audit Results

We are pleased to receive a highly positive result from the audit. No major issues were discovered. In their summary, Cure53 provided the following feedback(new window):

“Tested cryptographic implementations were top notch and excellent quality given the platform. The only limitations come from the platform itself (JavaScript/web), which do not allow for side channel resistance or reliable constant time operations. Overall however this is an exceptional library for JavaScript cryptography.”

As OpenPGPjs forms the foundation of Proton Mail’s encryption, this result provides extra certainty that Proton Mail’s cryptography is properly protecting users as intended. Working with the open source community is an important part of what we do at Proton Mail, and we will continue to build out the OpenPGPjs library. We are grateful to the Proton community for supporting us in these efforts.

Sign up and get a free secure email account from Proton Mail.

We also provide a free VPN service(new window) to protect your privacy.

Proton Mail and Proton VPN are funded by community contributions. If you would like to support our development efforts, you can upgrade to a paid plan or donate. Thank you for your support!

Protect your privacy with Proton
Get a free account

Share this page

Irina Marcopol

Irina is one of Proton's longest-serving team members, charged with strengthening and growing our brand and the Proton community. With a background in visual design, events management, and digital marketing, she strongly supports the protection of private data and contributes to building a better internet for generations to come.

Related articles

The first month of 2023 has brought brutal layoffs from Big Tech, a potential ban of TikTok in the US, and another Twitter breach. But the biggest development of this new year has to be the ascent of ChatGPT.  The chatbot can produce remarkably huma
Hackers were able to steal account details from over 200 million Twitter users and posted the database on a hacking forum in early January 2023. These details include users’ email addresses and Twitter handles, allowing people to potentially identify
From your online shopping receipts to financial statements, your emails contain a great deal of sensitive information about your life, interests, and daily schedule. If you’re concerned about your online privacy, it’s therefore vital to keep your inb
At Proton, we’re committed to building privacy-focused products that are convenient to use and improve your productivity. Last year, we released the new mobile apps for Proton Calendar and Proton Drive, letting you manage your schedule and upload imp
Most email services aren’t secure and limit attachment file sizes, but there are ways to send large files securely. If you’ve ever tried attaching multiple images or video files to an email, you’ll know that it doesn’t always work. We explain ways t
Email wasn’t initially designed to be secure. From spam and phishing attempts to malware, unethical marketers and cybercriminals try to undermine the security and privacy of your inbox every day. Since your inbox stores plenty of sensitive informatio