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
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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.