Is there anything similar to a QR code that works offline?
Say I have a flyer that I want to discreetly distribute and there is no internet.
Is there something like a QR code that contains the data itself and not just a URL?
This way someone with no data plan could scan the icon/code with an app and the unrecognizable bits and bytes from the icon/code would show up on their screen as a .JPEG of a flyer or something.
I just read about the error correction in QRCode; that’s pretty clever. Could an oppressed class obscure QRCodes enough to hide information from the oppressors while still communicating information?
you’re looking for steganography; I’m not aware of any steganographic constructions involving qrcodes, but there could be some. generally speaking, stego becomes practical in settings where there is unimportant high-entropy data which can be replaced with an encoding of the (typically encrypted) hidden message without altering the “cover” message in a detectable way. it might seem like this is the case with qrcodes due to the error correction; if you change a few random parts of the qrcode, due to the error correction it might still decode properly. However, this is probably easily detectable if the adversary has a high-resolution image of a candidate “maybe stego” qrcode: if decoding and re-encoding it produces a different qrcode, that would indicate that there had been extra data hidden in the error correction. (or, using a more advanced decoder than the typical ones, they could also simply see what the error rate is.)