Encryption and Digital Signing Query

Hi Shane

Thanks for the reply re Microsoft Update.

A query regarding encryption and digital signing. I am using Thunderbird 2 and Avast! 4.7 Home Edition. I have Avast! signing clean messages in and out. If a mail is either Digitally Signed or Encrypted, then presumably it is signed and/or encrypted prior to the Avast virus check as no signing is carried out by Avast either in or out.

Am I right in thinking that the order of processing is:-

Out Thunderbird>CSE>Avast
In Avast>CSE>Thunderbird

and that once encrypted or prior to decrypting it’s pointless Avast checking for a virus.
Also that Avast could not add it’s signature once encrypted/digitally signed as it would invalidate the certificate upon receipt.

Regards V

Hi

The answer to this question depends really at which point an AV cans e-mail and/or adds a scanned report to the e-mail.

Different AVs scan at different points. SecureEmail encrypts and signs at the network level but again it depends on each AV if it will be able to scan, some scan with mail client plug-ins.

The next versions of Comodo Anti Virus and Comodo Anti Spam will work in conjunction with SecureEmail to ensure that virus/spam can be carried out before the mail is encrypted.

Kind Regards,
Shane.

Hi Shane,

I see what you are saying but surely Secure Email should be developed to be compatible with the majority of AV’s that have virus detection for mail and not solely for in-house developed software.

I assume Avast Mail Server is Network based too as it sits monitoring the ports. I am not saying that it is a Secure Email problem, it may well be a problem with Avast. I was asking the question to try and attain a better understanding of the way it worked and highlight a possible compatibility issue.

Regards, V

Hi valldemossa,

I’ll go over these one by one below:

”I see what you are saying but surely Secure Email should be developed to be compatible with the majority of AV’s that have virus detection for mail and not solely for in-house developed software.”

SecureEmail is a client based application. It encrypts email on the client before it travels to the server (over SMTP, and decryption for POP3 and IMAP).

CSE encrypt the e-mails using S/MIME, just after they leave the e-mail client, in the client PC’s network stack. It’s also possible to encrypt e-mails using Outlook’s and Thunderbird’s S/MIME features, which encrypt in the e-mail client before even entering the network stack, like this

Outlook/Thunderbird ← Outlook TB Encrypt here
ComoeoSecureEmail ← CSE encrypt here, if not already encrypted
NetowrkStack
Network
MailServer ← Server based AV.
Internet

If your client based AV encrypts using a mail client plug-in it will probably scan before the mail leaves the mail client. This can obviously only be done for mail clients where plug-ins are possible and the mail client supplies enough functionality, which are few. If you encrypt your mail on your client PC then any server AV will have problems decrypting it and scanning it. There are a great deal of reason to encrypt at the client and not on a server gateway, especially to allow full journey encryption. Here’s a good report to look at to which gives a number of reasons why:

In the future CSE enterprises edition will have a feature set rich enough to allow the server to decrypt the mail and scan for viruses etc but this requires a server component that is user private key aware. SE will supply a large number of configurations to suit the needs of each particular enterprise.

”I assume Avast Mail Server is Network based too as it sits monitoring the ports. I am not saying that it is a Secure Email problem, “

You are correct, it’s actually a point of AV detection problem. By the very nature of encrypting something you are hiding and securing it, the whole point of the exercise. This also ensure the mail cannot be edited and the contents are indeed what was intended by the sender.

“it may well be a problem with Avast. I was asking the question to try and attain a better understanding of the way it worked and highlight a possible compatibility issue.”

Comodo SE tries to position itself in client the LSP network stack after all AV but this is not guaranteed (for Windows technical reasons) and installing an AV with network monitoring such as LSP, after SE may cause AV to be carried out after SE has encrypted the data. By the way, if you take SE out of the equation completely and encrypt using Thunderbird or Outlook, then a network monitoring AV will have no chance to scan the e-mails anyway.

It’s really a question of network topology and client software topology. You really need an AV with a client plug-in if you are encrypting with Outlook/TB alone, the same applies to SE but in a slightly lesser extent.

Hope this helps

Kind Regards,
Shane.

Hi Shane,

Thanks very much for your time and effort in giving that explanation, a brilliant response and much appreciated.
The problem with supplying such a detailed explanation is that it leads to more questions. However I’ll leave you to carry on the good work.

Best regards, V