Comments on: ECB vs CBC Encryption

By: Peter G.

Peter G. — Thu, 21 Feb 2013 11:39:47 +0000

Is it possible to get a visual feedback from a DES / T-DES OR DESX encryption as well?

By: Aaron Toponce

Aaron Toponce — Sun, 28 Oct 2012 14:43:47 +0000

Well, first all the commands are already in the post. You just need to reverse them. Second, because I took a bitmap header (54 bytes worth), and placed it on the encrypted data to create the image, there is irreversible data corruption on the encrypted data. For ECB, this won’t be a problem. For CBC, it will.

By: Shailja

Shailja — Sun, 28 Oct 2012 09:46:48 +0000

Can you tell me how to decrypt this image , because I tried but it shows some bad magic no
Please reply asap with the command

Thanks

By: Marcus Klaas

Marcus Klaas — Sat, 08 Sep 2012 16:11:45 +0000

Great post that explained EBC vs CBC really well. Thanks

By: Bryan

Bryan — Mon, 09 Jul 2012 02:57:46 +0000

This is a great demonstration, but I wonder if it might be made more accurate if the first 54 bytes of ubuntu.bmp were not included in the encryption. In the given example, the first 54 bytes are used in encryption, but then thrown away for visualization. It might be better to dd ubuntu.bmp to ubuntu-sans-header.bmp with bs=1 and skip=54. Perform encryption on ubuntu-sans-header.bmp and then append the 54 bytes from ubuntu.bmp as per the current example.

By: Aaron Toponce

Aaron Toponce — Mon, 04 Jun 2012 21:54:02 +0000

Yes. You’re absolutely correct. I’ll update the post. Thanks!

By: Martins Mozeiko

Martins Mozeiko — Sun, 03 Jun 2012 23:32:43 +0000

AES-256 doesn’t operate on 256-bit blocks at time. AES-128, 192 and 256 all operate on 128-bit blocks at time.
Only difference is in key size. That means expanded key size will be bigger and AES will use more rounds for AES-192/256 than for AES-128. 128 has 10 rounds, 192 has 12 rounds and 256 has 14 rounds

By: Jim

Jim — Sun, 26 Feb 2012 18:13:19 +0000

Fascinating. ECB looks like a terrible idea that should never be used to encrypt anything, as it makes no proper attempt to encrypt “whitespace”, or repeated runs of the same data in the input. The BMP clearly shows the effect, but other datasets (documents, audio, whatever) would be affected too.

By: Aaron Toponce

Aaron Toponce — Thu, 23 Feb 2012 02:15:07 +0000

Tiao- You need a browser that supports viewing bitmaps.

By: Tiao

Tiao — Thu, 23 Feb 2012 01:11:52 +0000

I cannot see the images in my bada phone.

By: Aaron Toponce

Aaron Toponce — Wed, 22 Feb 2012 12:12:48 +0000

shalombi- Yes, this isn’t a one-size-fits-all solution. And ECB definitely performs better than CBC in most cases. However, it is important to understand that patterns will emerge from the underlying data if you use ECB. It’s simple enough to do this same exercise on binary executables or text files, and see patterns emerge.

Regardless, the illustration with images is to help you understand what is happening with the different block modes.

By: shalombi

shalombi — Wed, 22 Feb 2012 07:56:06 +0000

ECB does preserve block structure which in the case of images reveals part of the information encrypted.
However this isn’t so much an issue with other types of data where the value lies in the data rather than the structure.

As explained CBC solves this by chaining the encryption but this comes with a performance hit.
So IMHO CBC isn’t a blanket solution but must be chosen carefully in regard with the task at hand.

http://www.cse.wustl.edu/~jain/cse567-06/ftp/encryption_perf/index.html#6

By: Ross

Ross — Wed, 22 Feb 2012 04:16:45 +0000

Very clever! Thanks for posting.

By: Aaron Toponce : Randomize First, Then Encrypt Your Block Device

Aaron Toponce : Randomize First, Then Encrypt Your Block Device — Mon, 20 Feb 2012 22:49:35 +0000

[...] blog post is in continuation of the previous post, where I showed why you should not use ECB when encrypting your data. Well, when putting down an [...]

By: anonymous

anonymous — Sat, 18 Feb 2012 15:45:07 +0000

Thanks for this illustration. That’s why some time ago i changed for IRC encryption from FiSH to mircryption which supports CBC