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How to encrypt image with AES algorithm?
Possibly using a library.
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How much is the size difference (increase/decrease)after encryption?
There would be no significative difference (data must be aligned to encription block, for instance 16 bytes, so you may experience a maximum increase of 'block size'-1 bytes).
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Is it possible to perform encryption with java script ?
Yes, using, precisely, a library, see for instance, this
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question:
"Javascript AES encryption"[
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