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.