Thomas Sibley

One takeaway is that disrupting/breaking QRs with a minimum of edits (and with only a sharpie) is a _lot_ easier than adversarially modifying one to data under your control. The crucial format bits which specify the code's error correction level and mask pattern is only 15 bits (5 data + 10 ECC). It appears in duplicate in the code, but many of those 30 bits will be dark already and you can black out the rest. As the layout of the bits is linear, it's easier to black out multiple bits at once.

@virtuous_sloth@cosocial.ca Nod. My hope is to better understand just how challenging/not simple it might be and how much changes can be intentionally minimized. For example, it seems there's opportunity to help a tool minimize changes by marking up which bytes in the encoded data it can have free reign over (vs must keep the same). Imagine a QR code that points to a short URL and you can create your own short URL that's one character different.