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What will really blow your mind is that you can cat a png and a zip together and the resulting file is both a valid png that looks identical to the image and a

What will really blow your mind is that you can cat a png and a zip together and the resulting file is both a valid png that looks identical to the image and a zip that contains the same contents as the archive.

Clewza313 5y ago
Mind. Blown. Only works if the PNG is first and the ZIP second though, because PNG reads front to back and ZIP reads back to front.
tinus_hn 5y ago
This is how these self extracting archives work, it’s just an exe (that allows adding random data to the end) and a zip (that allows random data to be prepended) added together.
- edub 5y ago
  more specifically the executable part contains the logic to decompress the remainder of the file, while still allowing a decompression program to be able to open and decompress the file (ignoring the executable portion of that file).
mike_d 5y ago
You might enjoy PoC||GTFO issue #10: > The polyglot file pocorgtfo10.pdf is valid as a PDF, as a ZIP file, and as an LSMV recording of a Tool Assisted Speedrun (TAS) that exploits Pokémon Red in a Super GameBoy on a Super NES. The result of the exploit is a chat room that plays the text of PoCkGTFO 10:3. https://www.alchemistowl.org/pocorgtfo/pocorgtfo10.pdf https://www.alchemistowl.org/pocorgtfo/pocorgtfo10.pdf
achairapart 5y ago
This may be also the trick used by the fantasy console PICO-8[0] which games run by png-based cartridges[1]. [0]: https://www.lexaloffle.com/pico-8.php https://www.lexaloffle.com/pico-8.php [1]: https://www.lexaloffle.com/bbs/?cat=7&carts_tab=1#sub=2&mode=carts&orderby=featured https://www.lexaloffle.com/bbs/?cat=7&carts_tab=1#sub=2&mode...
- dangerbird2 5y ago
  Apparently, Pico8 encodes the compressed app data directly in the PNG pixel data. They use 2 least significant bits of each color channel to encode a single byte of data per color. The pixel count of pico8 cartridges is what creates the console's 32,800 byte size limit. https://pico-8.fandom.com/wiki/P8PNGFileFormat https://pico-8.fandom.com/wiki/P8PNGFileFormat

Clewza313 5y ago

Mind. Blown. Only works if the PNG is first and the ZIP second though, because PNG reads front to back and ZIP reads back to front.

tinus_hn 5y ago

This is how these self extracting archives work, it’s just an exe (that allows adding random data to the end) and a zip (that allows random data to be prepended) added together.

edub 5y ago
more specifically the executable part contains the logic to decompress the remainder of the file, while still allowing a decompression program to be able to open and decompress the file (ignoring the executable portion of that file).

mike_d 5y ago

You might enjoy PoC||GTFO issue #10: > The polyglot file pocorgtfo10.pdf is valid as a PDF, as a ZIP file, and as an LSMV recording of a Tool Assisted Speedrun (TAS) that exploits Pokémon Red in a Super GameBoy on a Super NES. The result of the exploit is a chat room that plays the text of PoCkGTFO 10:3. https://www.alchemistowl.org/pocorgtfo/pocorgtfo10.pdf https://www.alchemistowl.org/pocorgtfo/pocorgtfo10.pdf

achairapart 5y ago

This may be also the trick used by the fantasy console PICO-8[0] which games run by png-based cartridges[1]. [0]: https://www.lexaloffle.com/pico-8.php https://www.lexaloffle.com/pico-8.php [1]: https://www.lexaloffle.com/bbs/?cat=7&carts_tab=1#sub=2&mode=carts&orderby=featured https://www.lexaloffle.com/bbs/?cat=7&carts_tab=1#sub=2&mode...

dangerbird2 5y ago
Apparently, Pico8 encodes the compressed app data directly in the PNG pixel data. They use 2 least significant bits of each color channel to encode a single byte of data per color. The pixel count of pico8 cartridges is what creates the console's 32,800 byte size limit. https://pico-8.fandom.com/wiki/P8PNGFileFormat https://pico-8.fandom.com/wiki/P8PNGFileFormat