Adding Digital signature to Emails increase size

[Amihai Bareket]

I've been testing the use of digital signatures with Outlook 2003 & Exchange
2003.
I've noticed that when I sign an Email it increases it's size by 37%.
This can be quite large increase when dealing with Email that has large
attachments.

Is this a normal behavior or configuration problem?

 

[Vizvary Istvan III]

This is normal behavior. When you sign a message, you're actually making
a multipart/MIME message; one of the parts will be the signature. The
exact size expansion will vary depending on whether you're using clear
signing or opaque signing, and which parts of the certificate chain the
message includes.

In fact, the 37% factor suggests opaque sigining, which is usually encoded
with Base64.

Vizvary Istvan III
http://www.cryptigo.com