Does DomainKeys hogs my server CPU ?

[infogalera]

Hi,

I have activated DomainKeys on all my server domains (about 50). Everything worked fine until one user send a message with a 8 Mb file attached to 50 destinations.

My served resulted complete unresponsable. Luckly I had "top" running in the ssh and i could monitor was happening.

A lot of "executable" processes were running concurrently like this:

3358 qmailq 17 0 3768 832 680 D 0.3 0.2 0:00.17 executable


Load average exceeded 100

top - 13:26:45 up 27 days, 21:55, 2 users, load average: 103.40, 75.55, 38.17


Is DomainKeys overloading the processor? I haven't changed anything else.


Best regards,
Alex

 

[wsani]

DomainKey is nothing but a string in the DNS zone.

 

[infogalera]

Hi

According Wikipedia:
http://en.wikipedia.org/wiki/DomainKeys

How it works
DomainKeys adds a header named "DomainKey-Signature" that contains a digital signature of the contents of the mail message. The default parameters for the authentication mechanism are to use SHA-1 as the cryptographic hash and RSA as the public key encryption scheme, and encode the encrypted hash using Base64.
The receiving SMTP server then uses the name of the domain from which the mail originated, the string _domainkey, and a selector from the header to perform a DNS lookup. The returned data includes the domain's public key. The receiver can then decrypt the hash value in the header field and at the same time recalculate the hash value for the mail body that was received, from the point immediately following the "DomainKey-Signature:" header. If the two values match, this cryptographically proves that the mail originated at the purported domain and has not been tampered with in transit.

Protocol overhead
DomainKeys requires cryptographic checksums to be generated for each message sent through a mail server, which results in computational overhead not otherwise required for e-mail delivery.

So, has the server to calculate the hash value for every message (including attached files?) ?