WHAT THE SCANNER SEES
EXHIBIT 03
THE CORRECTION BUDGET
Damage can be data, until it is too much damage.
Reed-Solomon codewords let a reader repair limited symbol errors. Deliberate changes can carry a second signal, but every changed codeword spends part of the same budget needed for scratches, blur, and missing modules.
LIVE MULTI-BLOCK LAB / WAN-STYLE REGION OPTION
LIVE CORRECTION LAB
Spend the margin
One highlighted module is flipped in each selected codeword. ZXing independently decodes the modified matrix after every change.
The same number of altered codewords is distributed round-robin across Reed-Solomon blocks.
CORRECTION BUDGET—
WHAT CHANGED UNDERNEATH
WHAT A SECOND READER CAN RECOVER
HOW AN ANALYST CAN NOTICE
IDEA LINEAGE
Correctable changes became a family of channels.
- 2013-2018QR steganography literature
Use correctable module or codeword changes for secondary data, with different capacity and robustness tradeoffs.
Wan et al. - THIS LABBlock-local correction experiment
Hold the error count fixed, change only placement, and ask an independent decoder what survives.
FINDING
Error correction is a robustness reserve, not free capacity.
Changing a module in a distinct codeword creates a Reed-Solomon symbol error. A decoder can often restore the overt message while those errors remain within every block's correction limit. Hiding and environmental damage compete for that same finite margin.
Research basis: this generalized laboratory illustrates the family of correctable-change techniques cited in Chiang et al. (2013), Bui et al. (2014), Lin & Chen (2017), Huang et al. (2018), and Wan et al. (2017/2018). The lower-right data-region option follows Wan's spatial rule, while the spread/concentrate comparison isolates the paper's per-block limit. It does not reproduce the paper's maximum-region calculation for every QR version.
Read the research note