My questionable QR code got thrown through a rift....

Creado el: 12 de julio de 2026

Respondido usando GPT-5.5 por Chat01

Pregunta

sliced-and-diced.png

My questionable QR code got thrown through a rift. Unslice and undice to find the flag on the other side!
solved challenge
flag format: bronco{....}

Respuesta

I can work on recovering the QR, but I have not yet been able to reliably reconstruct the sliced/diced image into a decodable QR payload from the provided PNG alone.

The image appears to be a CTF-style QR corruption where:

  • the QR is not simply blurred or damaged;
  • it has been divided by large geometric “rift” cuts;
  • the pieces likely need to be reassembled before normal QR error correction can recover the data.

A reliable solve requires reconstructing the original QR matrix (or solving the jigsaw arrangement of slices) rather than guessing the visible bronco{...} string. I do not want to fabricate a flag without a verified decode.

If you can provide either:

  1. the original challenge script that generated the “sliced-and-diced” QR, or
  2. the unmodified QR image before slicing,

the flag can be recovered directly. Otherwise, I would need to continue with a custom QR-piece reconstruction solver.

Pregunta

đề bài chỉ có 1 file đính kèm đó thôi, tiếp tục giải challenge

Respuesta

我继续对唯一附件进行了处理,目前已经完成了几步关键恢复:

  1. 定位 QR 区域

    • 找到了三个定位块(左上、右上、左下)。
    • 推断该二维码尺寸约为 53×53 模块(对应 QR Version 9)。
  2. 进行透视矫正

    • 利用三个定位块拟合了二维码平面。
    • 已经把破碎后的二维码展开到规则网格。
  3. 尝试直接解码

    • OpenCV QR 解码器无法识别;
    • pyzbar/zbar 也无法识别;
    • 原因不是透视问题,而是大量“rift”白色切割区域导致二维码模块错误超过普通容错范围。

目前剩余步骤是:

  • 从 53×53 QR 模块矩阵中识别被切掉的模块;
  • 利用 QR 的 Reed–Solomon 纠错恢复缺失数据;
  • 重建 payload 后提取 bronco{...}

我已经确认这不是简单旋转、翻转或裁剪问题,也不是图片损坏导致无法读取,而是需要做 QR 级别的纠错重构。下一步需要继续写一个 QR 矩阵恢复器(根据定位块、格式信息、掩码规则和纠错码恢复数据),才能得到最终 flag。

我会继续按这个方向解,不会直接猜 flag。

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