Has Email Crypto Been Broken? No!

When the EFF (Electronic Frontier Foundation) announce that you should immediately uninstall a piece of software and stop using it, you take notice.

Lack of trust

We need to realise quite soon that email, as a concept, is old and cannot fit with our modern standards of security. Mostly, it is insecure and has low levels of trust. It also provides a mechanism for a large-scale data leakage from companies. So what are the alternatives? Well, apart from Signal and WhatsApp, PGP (Pretty Good Privacy) is one of the few methods around that can both protect and sign electronic mail.

But yesterday a new PGP vulnerability - EFAIL [here] - was announced by Sebastian Schinzel, and who is a computer security professor at Münster University of Applied Sciences. He defined that an attacker could intercept an encrypted email and can inject code into the encrypted message and which modifies the loading of external content (such as images and remote pages). This can then be used to compromise the local machine.

A few points here:

• The encryption and signing process has NOT been broken. The problem relates to the sloppiness of humans in coding the email clients. It is thus the email package which reads the email which has the problem. An easy fix is just to stop the loading of external content (which, in a secure infrastructure, is a good idea).
• The capturing of encrypted emails is actually a difficult thing to do, especially as they are likely to be sent over encrypted tunnels.
• Few people actually use PGP any more, as it's not an easy system to use. For many the focus is on Signal or WhatsApp, and which provide complete end-to-end encryption, with unique keys used for every connection.
• If you use OpenPGP properly, the exploit will have no relevance.

The EFF thus advised users that there are no current fixes and that they should uninstall PGP and S/MIME applications until the flaws are patched. While the EFF message looks alarmist, the vulnerability is nowhere on the scale of a Heartbleed or WannaCry, and could have limited scope for compromises of data.

The full details of the vulnerability will be released today (Tuesday), so I'll be posting details on the technical nature of it.

PGP (Pretty Good Privacy)

Phil Zimmerman came up with the best way to achieve both the signing of an email and to preserve the privacy with PGP:

With PGP, we sign a hash of the message with our private key, so that the other side can check the sender (and that the message hasn't been changed). We then create a new encryption key for every message, and then just need to encrypt this key with the other side's public key. The receiver then receives the message, and decrypts the email encryption key with her private key, and reads the message. After she takes a hash of the message, and then decrypts the encrypted hash with Bob's public key, and checks the result. If the values match, she has proven the sender and that the message hasn't been changed ...

So what has gone wrong in the adoption of secure email? Well, we haven't found a method where users can easily register their public keys, and for software to support the proper signing of email. Microsoft Exchange has never really properly supported signing and encryption, and it is left to third-party plug-ins, which aren't easy to use.

So, do you have a public key that you publicise? Here is my public key: 

https://asecuritysite.com/encryption/pgp1

 If you're interested in how to create one and encrypt data, here is a tutorial in using PGP:

https://asecuritysite.com/public/csn11123_lab08.pdf

For many, though, especially governments, the use of public keys for email is something that scares a whole lot of people.