Why AES based encryption is not recommended for encrypting images with high redundancy in their content? for example, the encryption of an image which shows a bird in the blue sky. Most of the pixels are blue in that case.
closed as not a real question by Paŭlo Ebermann♦ Oct 22 '12 at 19:08
It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center.If this question can be reworded to fit the rules in the help center, please edit the question.
What do you mean "AES is not recommended for highly-redundant images"?
Perhaps you're referring to "ECB mode is not recommended for highly-redundant images" (and yes, AES can be used for ECB mode).
Yes, AES in ECB mode is not recommended for highly-redundant images, because it doesn't disguise when two 128 bit plaintext blocks are exactly the same. Here is a famous example of a drawing of the Linux penguin encrypted using ECB mode:
As you can see, you can make out significant details of the original image.
AES in other modes (CBC, CFB, Ctr, GCM) doesn't have this weakness, and so are strongly preferred.