Re: AES with constant key

On 6 מרץ, 16:58, biject <biject.b...@xxxxxxxxx> wrote:
On Mar 6, 6:19 am, MajorSoul <MajorS...@xxxxxxxxx> wrote:

Hi,

Suppose I have a public AES engine with a constant key.
cleartext data comes to the engine, encrpyted with the same key all
the time and goes out ciphertext data to the sender.

can someone use the ciphertext data, my AES engine with constant key
to get back the cleartext data?

is this problem a famous crypto quesiton? if so, can you send me links
and ofcourse the answer :)

thanks,
MS

 Here is a link you might want as a starthttp://en.wikipedia.org/wiki/Unicity_distance

 As most here will immediately jump to and say its impossible to
randomly
guess all 256bit key to solve this problem.

 But if the message file you encrypt say with straight AES ECB mode
They could
problably guess the plain text a piece at a time to get the message by
trail and error. And thats if AES is perfect which is not likely. Very
few people do proper whitening and/or proper compression before the
encryption pass. Which would make this kind of attack much harder
to do.

  Its my belief that most crypto people spend there time on forums
like this
to trick people into using weak crypto so that the big 3 letter
agencies
can do there job of reading peoples mail.  Its real hard to test
crypto for
the small weakness they could be in it. So its best to make it as
secure as reasonablly possible in the Shanon sense before you use
the herd encryption method. As a first layer use your own method and
of course a bijective compressor as the very first past.

  Here is method that uses full size AES 256 where if you had the same
problem
as before its not likely even as weak as AES might be for an attacker
to
do anything similar to the above meothod

 make your key 3 times as long one for each pass of BICOM
pass one use BICOM  to compress and encrypt the plain text file
use UNBWTS on the result to further whiten the file.
Next pass do BICOM uncompress with the next key. and then
do a plain BWTS and compress encrypt again with the third
key.  Even if AES is weak every stage here is bijective and it
should result in a whitened compressed encrypted file that
will be harder to break even in the black box situation that you
mention.

David A. Scott
--
 My Crypto codehttp://bijective.dogma.net/crypto/scott19u.ziphttp://www.jim.com/jamesd/Kong/scott19u.zipold version
My Compression codehttp://bijective.dogma.net/
**TO EMAIL ME drop the roman "five" **
Disclaimer:I am in no way responsible for any of the statements
 made in the above text. For all I know I might be drugged.
As a famous person once said "any cryptograhic
system is only as strong as its weakest link"

Thanks for the response.

Lets make it easier. AES with 128 bit key. EBC mode.
I was shooting more into the direction of reformating an encrpyted
block and encrpyting it again to get the original clear text.

is that engine called oracle or something like that? do you have a
link which list attacks using oracls?

Thanks,
MS
.

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