You are right about AES-CBC. Palatalization of block encryption is not really possible. If you want to encrypt blocks in parallel then you should use AES-CTR.
Kris --------- Original Message -------- From: [email protected] To: Erwann Abalea <[email protected]> Cc: [email protected] Subject: Re: [openssl-users] specifying the number of rounds that I would like to use with AES-192-CBC Date: Mar 13, 2013 10:18 PM > I'm quite new to openSSL and AES and cryptography as a whole, so > please forgive my "stupid" questions. > > I've read that because of the way that the AES-CBC works that it > depends on the result from the previous round in order to encrypt the > current round that it is inherently not well suited for > parallelization; which I am then guessing that it is very possible > that it would run (a LOT) slower on GPGPU than it would on an AES-NI > enabled CPU. Would that be a fair and safe assumption? > > I'm also looking online and through the man pages and it seems like > that people are invoking the aesni by using the command: > > openssl -engine aesni -evp aes-256-cbc ... > > what's the '-evp' flag for? > > On Wed, Mar 13, 2013 at 12:12 PM, Erwann Abalea > <[email protected]> wrote: > > GPGPU isn't natively supported. You can write your own engine if you want, > > but I think memory transfers will dominate the cost. > > AES-NI is natively supported (I get about 550MB/s on my i5 M540 @2.53 GHz > > for 8k blocks). > > > > -- > > Erwann ABALEA > > > > Le 13/03/2013 16:49, Ewen Chan a écrit : > >> > >> Would it be faster to encrypt/decrypt AES-256-CBC with an AES-NI > >> enabled CPU or would it faster do it with a GPGPU? > >> > >> Does OpenSSL even support GPU acceleration? > >> > >> On Wed, Mar 13, 2013 at 11:44 AM, Ewen Chan <[email protected]> wrote: > >>> > >>> Thanks. > >>> > >>> On Wed, Mar 13, 2013 at 10:56 AM, Erwann Abalea > >>> <[email protected]> wrote: > >>>> > >>>> The algorithm "Rijndael" has some knobs you can turn to tune. > >>>> The standard "AES" has these parameters fixed in stone. > >>>> > >>>> AES-192 is effectively "less secure" than AES-256 because of the key > >>>> length > >>>> and number of rounds. > >>>> But "less secure" may be "secure enough". In fact, AES-128 is secure > >>>> enough > >>>> for most uses. > >>>> Number of rounds is important for AES security as it is for any other > >>>> algorithm (think about attacks on reduced-rounds AES/SHA/whatever). > >>>> > >>>> -- > >>>> Erwann ABALEA > >>>> > >>>> Le 13/03/2013 15:31, Ewen Chan a écrit : > >>>> > >>>>> So the algorithms include the number of rounds? I thought that it > >>>>> would only describe the math process and that it would be independent > >>>>> of the number of rounds (so long as you meed Rijndael's "minimum" - > >>>>> which is what the current number of rounds is set/default as). > >>>>> > >>>>> I did not know that. Hmmm....thanks. > >>>>> > >>>>> Does this mean that a AES-192-CBC is less secure than an AES-256-CBC > >>>>> because of the key length and the number of rounds associated with > >>>>> that; or am I understanding that wrong - that the number of rounds has > >>>>> less-so to do with the security of the algorithm compared to the key > >>>>> length? > >>>>> > >>>>> On Wed, Mar 13, 2013 at 10:24 AM, Erwann Abalea > >>>>> <[email protected]> wrote: > >>>>>> > >>>>>> If you change the number of rounds, then it's not AES anymore, but a > >>>>>> custom > >>>>>> Rijndael. > >>>>>> Reading the source code, it appears there's no support for that in > >>>>>> OpenSSL > >>>>>> (and poking inside an AES_KEY to change the number of rounds probably > >>>>>> won't > >>>>>> work). > >>>>>> > >>>>>> -- > >>>>>> Erwann ABALEA > >>>>>> > >>>>>> Le 13/03/2013 14:32, Ewen Chan a écrit : > >>>>>> > >>>>>>> There's a file that I want to encrypt using AES-192-CBC but with 19 > >>>>>>> rounds rather than the default 12-rounds. > >>>>>>> > >>>>>>> Is there a way for me to specify the number of rounds that I would > >>>>>>> like to use with the AES-192-CBC? (and override the algorithm > >>>>>>> defaults)? > >>>>>>> > >>>>>>> Is that something that I can within the openssl command itself (to > >>>>>>> encrypt a file) or is the process much more involved than that? And > >>>>>>> requires programming/scripting? > >>>>>> > >>>>>> > >> ______________________________________________________________________ > >> OpenSSL Project http://www.openssl.org > >> User Support Mailing List [email protected] > >> Automated List Manager [email protected] > >> > > > ______________________________________________________________________ > OpenSSL Project http://www.openssl.org > User Support Mailing List [email protected] > Automated List Manager [email protected] > Sent to you using Uebimiau Webmail version 3.11 Developed by Dave and Todd at http://www.manvel.net and http://www.tdah.us ______________________________________________________________________ OpenSSL Project http://www.openssl.org User Support Mailing List [email protected] Automated List Manager [email protected]
