Re: AES counter mode

Kostantinos Koukopoulos <[email protected]> writes:

>Thank you for your quick answer. One clarification, with CBC I can start/stop
>the process if I save the last ciphertext block along with key and IV,
>correct? 

Yes.  Well, the previous ciphertext block is the IV, so all you need is the
key, there's no need to maintain an explicit IV.

>Also am I wrong to say that I cannot encrypt the plaintext blocks in parallel
>since I need to have already encrypted all previous blocks to encrypt the
>next one?

Yes.  OTOH unless you're using specialised crypto hardware you can't do much
in parallel for CTR either, you're still only doing on ECB block at a time.
Intel has published whitepapers showing impressive results from
parallelisation with e.g. 6 cores and 12 threads, but it's unclear whether you
could ever do that in a real-world environment, you'd need to grab control of
every thread on every core for your own use which I suspect no OS would let
you do.

(Also, CBC mode can be run in parallel for decryption, it's only encryption
that's serialised).

Peter.

_______________________________________________
Cryptlib mailing list
[email protected] via Mail: [email protected]
Archive: ftp://ftp.franken.de/pub/crypt/cryptlib/archives/
http://news.gmane.org/gmane.comp.encryption.cryptlib
Posts from non-subscribed addresses are blocked to prevent spam, please
subscribe in order to post messages.