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

David Shaw dshaw at
Mon Sep 27 15:57:18 CEST 2010

On Sep 24, 2010, at 4:29 PM, Daniel Kahn Gillmor wrote:

> Are there other interpretations of the above results?  does anyone else
> want to post comparable data points on different hardware?  How powerful
> is a typical smartphone anyway?  What kind of a cutoff are people
> willing to accept in terms of CPU cycles per signature validated?  or am
> i measuring the wrong thing entirely?

Sort of, yes.  You are measuring verify performance.  At it happens, that is the operation that RSA really excels at, CPU-wise.  Try measuring signing or decryption performance instead.  People on smartphones don't just verify signatures :)

"Dreadfully" is a difficult thing to enumerate anyway.  For me, FWIW, it would be "over 1-2 seconds".


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