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

[Vjaceslavs Klimovs]

On 27/09/10 16:21, Jameson Rollins wrote:
> On Mon, 27 Sep 2010 15:56:52 +0200, Vjaceslavs Klimovs <vklimovs at gmail.com> wrote:
>> I did some quick tests on Nokia N900 (600 MHz ARM CPU), with gnupg
>> 1.4.6, here is what I got:
>>
>> Encrypting and signing, 2048 bit RSA keys:
>>
>> real    0m 2.50s
>> user	0m 0.50s
>> sys	0m 0.02s
>>
>> Decrypting and verifying, 2048 bit RSA keys:
>>
>> real	0m 1.74s
>> user	0m 0.41s
>> sys	0m 0.04s
>>
>> Encrypting and signing, 4096 bit RSA keys:
>>
>> real    0m 3.58s
>> user	0m 1.92s
>> sys	0m 0.06s
>>
>> Decrypting and veryfying, 4096 bit RSA keys:
>>
>> real	0m 3.80s
>> user	0m 1.89s
>> sys	0m 0.03s
>>
>> Is one second considered a rule of thumb limit? That would mean that
>> 4096 keys are not suitable for widespread use yet.
> 
> Then by that logic neither are 2048 bit keys.
> 
> jamie.

2048 bit keys are suitable - it's "user+sys" what matters in this case,
but not "real" by all means, as that includes waiting for passphrase
input too.