While attending a water class, I followed Discord to try and get an invitation code to play, but my reaction speed was too slow. By the time I saw the codes that were given directly or only masked a single digit, they were basically gone. However, I then saw the following riddle:
The result of scanning the code is: the invitation code is hidden "inside" the image.
OK, this successfully sparked my desire for a challenge 🤓
Although I knew it was unlikely to be something simply embedded visually in the image, I still stared at it for a minute. I also asked 4o to do some multimodal analysis, and as expected, the outcome was fruitless.
So it was likely hidden like a watermark (I can only guess since I don't know much about the related technology). AI suggested it might be LSB (Least Significant Bit) steganography, with the basic principle as follows:
It also recommended the Stegsolve tool. I have to praise devv.ai's 3.5 Sonnet + online search, which is really powerful. Then I searched online to see if there was a directly usable online version, and thus the main character of this episode arrived:
https://georgeom.net/StegOnline
The result was instant success... The process of cracking was not as difficult as I imagined, thanks to the kindness of the expert~