AES and DSA speeds

Hello.

I have a very practical question. One year ago we developed an embedded
system which had to perform DSA signatures by software on some messages
(about 100 bytes long).

We used 512 bits key for this. This takes our modest general-purpose CPU
about 10 seconds per message.

Now, we have to encrypt some of these messages. We are planning to use
AES with 128 or 256 bits keys.

And the question is: approximately, how much time should we expect this
encryption to take? Much more than 10 seconds? Much less? Same order of
magnitude?

When I first met encryption 10 years ago, it was "popular wisdom" that
simmetric key algorithms (like DES) were faster than public key ones
(like DSA or RSA). But AES was inexistent then, and I don't know if its
speed compares favourably to DES's speed or not.

I know that the correct answer depends on the implementation, so I am
asking only for a rough estimate.

Pointers are welcome. Many thanks.

Re: AES and DSA speeds

Ignacio G.T. wrote:
<...>
> Now, we have to encrypt some of these messages. We are planning to use
> AES with 128 or 256 bits keys.
>
> And the question is: approximately, how much time should we expect this
> encryption to take? Much more than 10 seconds? Much less? Same order of
> magnitude?

I've seen an estimate that AES runs four times faster than DES. The
length of the key has only a little impact on speed.

-- Lassi

Re: AES and DSA speeds

Ignacio G.T. wrote:
> system which had to perform DSA signatures by software on some messages
> (about 100 bytes long).
> We used 512 bits key for this. This takes our modest general-purpose CPU
> about 10 seconds per message.
> Now, we have to encrypt some of these messages. We are planning to use
> AES with 128 or 256 bits keys.
> And the question is: approximately, how much time should we expect this
> encryption to take? Much more than 10 seconds? Much less? Same order of
> magnitude?

Please explain, what kind of CPU you're using.

Yours,
VB.
--
Wenn Du "Ich sehe die Mathematik als einzigen Bereich an, wo es klare
Beweise gibt." und "Ich fuehle mich in einem Anzug unwohl." als Aussagen
mit aequivalentem Meinungsinhalt betrachtest, hast Du mit Deinem Gleichnis
recht. (Michail Bachmann zu Thomas Wallutis in d.a.s.r)

Re: AES and DSA speeds

Lassi Hippeläinen escribió:
> Ignacio G.T. wrote:
> <...>
>> Now, we have to encrypt some of these messages. We are planning to use
>> AES with 128 or 256 bits keys.
>>
>> And the question is: approximately, how much time should we expect
>> this encryption to take? Much more than 10 seconds? Much less? Same
>> order of magnitude?
>
> I've seen an estimate that AES runs four times faster than DES. The
> length of the key has only a little impact on speed.
>

Thanks, Lassi. Remember where did you see that?

Re: AES and DSA speeds

Ignacio G.T. wrote:

> Lassi Hippeläinen escribió:
>> Ignacio G.T. wrote:
>> <...>
>>> Now, we have to encrypt some of these messages. We are planning to use
>>> AES with 128 or 256 bits keys.
>>>
>>> And the question is: approximately, how much time should we expect
>>> this encryption to take? Much more than 10 seconds? Much less? Same
>>> order of magnitude?
>>
>> I've seen an estimate that AES runs four times faster than DES. The
>> length of the key has only a little impact on speed.
>>
>
> Thanks, Lassi. Remember where did you see that?

It was many years ago, probably in sci.crypt, when I was still keeping an
eye on how the story AES unfolds. Try asking there. You can probably find
an implementor with personal experience.

-- Lassi

Re: AES and DSA speeds

AES 2 runs about 4 times as fast too.