CODEWITHSUNDEEP
encodingdecodingsteganography
Siya Mzam
Siya Mzam

Reputation: 4705

Recovering and Reordering Lost Bytes

When an image is sent to an application (e.g WhatsApp) over the network, the image is compressed to an extent.

How can I recover these lost bytes and when I do, how can I regain the order in which they were, originally?

Use case for this is in the application of Steganography. if I encode a message into a png, send it over WhatsApp, and download it back (comes back as jpeg in WhatsApp's case), convert it back to PNG, I cannot seem to decode the message again as I would with the picture that never went over the network.

Upvotes: 0

Views: 44

Answers (1)

Reti43
Reti43

Reputation: 9797

You're dealing with a noisy channel, which may intentionally or unintentionally alter your data in transit, so you need to ensure your algorithm is robust to that. In this case you want an algorithm robust to lossy recompression, assuming nothing else takes place, e.g., resizing, cropping, etc.

I would start with a literature review to find an algorithm that fits any other lower priority criteria you may have. Keep in mind that the algorithm will probably end up being more complex compared to simply altering pixel values directly, which can be done in a few lines of code. Especially if the algorithm is only applicable to jpeg images. And it's likely it'll implement some kind of error correction, which will decrease your message capacity.

Upvotes: 1

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