The Internet’s two most widely used methods for encrypting e-mail–PGP and S/Mime–are vulnerable to hacks that can reveal the plaintext of encrypted messages, a researcher warned late Sunday night. He went on to say there are no reliable fixes and to advise anyone who uses either encryption standard for sensitive communications to remove them immediately from e-mail clients.
The flaws “might reveal the plaintext of encrypted emails, including encrypted emails you sent in the past,” Sebastian Schinzel, a professor of computer security at Münster University of Applied Sciences, wrote on Twitter. “There are currently no reliable fixes for the vulnerability. If you use PGP/GPG or S/MIME for very sensitive communication, you should disable it in your email client for now.”
Schinzel referred people this blog post published late Sunday night by the Electronic Frontier Foundation. It said: “EFF has been in communication with the research team, and can confirm that these vulnerabilities pose an immediate risk to those using these tools for email communication, including the potential exposure of the contents of past messages.”
The research team members have been behind a variety of other important cryptographic attacks, including one from 2016 called Drown, which decrypted communications protected by the transport layer security protocol. Other researchers behind the PGP and S/MIME research include Damian Poddebniak, Christian Dresen, Jens Müller, Fabian Ising, Simon Friedberger, juraj somorovsky, and Jörg Schwenk. Besides Münster University, the researchers also represent Ruhr-University and KU Leuven University.
Given the track record of the researchers and the confirmation from EFF, it’s worth heeding the advice to disable PGP and S/MIME in e-mail clients while waiting for more details to be released Monday night. Ars will publish many more details when they are publicly available.