Implementation of Chosen-Ciphertext Attacks against PGP and GnuPG
by Kahil Jallad, Jonathan Katz and Bruce Schneier
We recently noted that PGP and other e-mail encryption protocols are, in theory, highly vulnerable to chosen-ciphertext attacks in which the recipient of the e-mail acts as an unwitting "decryption oracle". We argued further that such attacks are quite feasible and therefore represent a serious concern. Here, we investigate these claims in more detail by attempting to implement the suggested attacks. On one hand, we are able to successfully implement the described attacks against PGP and GnuPG (two widely-used software packages) in a number of different settings. On the other hand, we show that the attacks largely fail when data is compressed before encryption.

Interestingly, the attacks are unsuccessful for largely fortuitous reasons; resistance to these attacks does not seem due to any conscious effort made to prevent them. Based on our work, we discuss those instances in which chosen-ciphertext attacks do indeed represent an important threat and hence must be taken into account in order to maintain confidentiality. We also recommend changes in the OpenPGP standard to reduce the effectiveness of our attacks in these settings.

Download the paper in PDF format here.

Spotlight

Biggest ever cyber security exercise in Europe is underway

Posted on 30 October 2014.  |  More than 200 organisations and 400 cyber-security professionals from 29 European countries are testing their readiness to counter cyber-attacks in a day-long simulation, organised by the European Network and Information Security Agency (ENISA).


Weekly newsletter

Reading our newsletter every Monday will keep you up-to-date with security news.
  



Daily digest

Receive a daily digest of the latest security news.
  

DON'T
MISS

Fri, Oct 31st
    COPYRIGHT 1998-2014 BY HELP NET SECURITY.   // READ OUR PRIVACY POLICY // ABOUT US // ADVERTISE //