[HN Gopher] Hide a photo inside another photo
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       Hide a photo inside another photo
        
       Author : avestura
       Score  : 28 points
       Date   : 2022-04-28 20:35 UTC (2 hours ago)
        
 (HTM) web link (www.avestura.dev)
 (TXT) w3m dump (www.avestura.dev)
        
       | 1970-01-01 wrote:
       | Check out https://en.m.wikipedia.org/wiki/Steganography if this
       | is your thing
        
       | dennis-tra wrote:
       | Steganography is a very exciting topic and is not limited to
       | image data but can also be applied to, e.g., audio data.
       | 
       | I've done something similar in the past and embedded Merkle tree
       | nodes in an image to allow partial integrity validation. It was a
       | fun little project:
       | 
       | https://github.com/dennis-tra/image-stego
        
       | gregorymichael wrote:
       | "A picture of you, holding a picture of me, in the pocket of my
       | blue jeans."
        
       | noasaservice wrote:
       | Hmm.
       | 
       | So combined with Apple's CSAM scanner, you can put CSAM inside a
       | cat photo... And then anonymously leak the cat photo and tool to
       | show it's CSAM. And then the CSAM scanner will flag the hash and
       | alert the police of the user.
       | 
       | And the target victim would never know.
        
         | woodruffw wrote:
         | This is substantially more complicated than finding a collision
         | against the perceptual/"content aware" hash that Apple was
         | planning on using.
        
       | japhib wrote:
       | This is how PICO-8 game cartridges are contained in a small PNG
       | of the game itself!
       | 
       | https://www.lexaloffle.com/pico-8.php
       | 
       | https://robertovaccari.com/blog/2021_01_03_stegano_pico8/
        
         | dividuum wrote:
         | Interesting. I always thought they'd use some PNG chunk
         | (comment?) for that.
        
       | jstanley wrote:
       | Ages ago I made a tool that does a similar method (rewrite the
       | least-significant N bits of a pixel in the cover image with the
       | most-significant N bits of the corresponding pixel of the hidden
       | image). In my tool N is configurable.
       | 
       | The main pitfall is that it doesn't work very well if the output
       | is saved as a JPEG because of the compression.
       | 
       | I think OP's idea of encoding _all_ of the bits of the hidden
       | image, by using a cover image with more pixels, is a good
       | improvement: you get no loss of quality in the hidden image, and
       | you vastly reduce the loss of quality in the cover image.
       | 
       | https://incoherency.co.uk/image-steganography/
        
       | pmoriarty wrote:
       | Videos provide much more space to hide data in than your typical
       | images do.
       | 
       | I've always wondered if there was some way that hidden
       | information inside videos could be designed to survive the re-
       | encoding that youtube does when you upload a video.
       | 
       | Has anyone investigated this?
        
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       (page generated 2022-04-28 23:00 UTC)