how slow are 4Kbit RSA keys? [was: Re: multiple keys vs multiple identities]

David Smith Dave.Smith at
Mon Sep 27 11:12:41 CEST 2010

Daniel Kahn Gillmor wrote:
> On 09/24/2010 09:54 AM, David Shaw wrote:
>> It won't work with the current generation of OpenPGP smartcards.  It also 
>> will be dreadfully slow if you (or someone you are communicating with) ever
>> uses the key on a small machine (think smart phone).  If you are usually on
>> a "full power" computer, then they generally have the CPU to spare for this
>> sort of thing, and you'll rarely if ever notice a difference.
> i'm curious to see some quantitative data about what "dreadfully slow"
> means.

Not truly "quantitative, but I notice a significant difference between
encrypting emails to people with 1024-bit keys vs people with 4096-bit
keys.  I'd say that the difference is in the order 3-6 seconds.

I'm running GnuPG 1.4.x on a Sun Ultra10 with a 500 MHz CPU and 1 GB
RAM.  Yes, I know it's old.  :-)

We're forced to use 4096-bit keys because some of our customers require it.

More information about the Gnupg-users mailing list