# DownUnderCTF: masked-squares flag checker

> An official educational challenge investigation connects binary checks to equations and records an original-program validation.

- Type: Case study
- Targets: Binary
- Category: Official REA: case studies
- Relationship: Official REA case study
- Sources reviewed: 2026-10-15
- Added to the catalog: 2026-10-16
- Original resource: <https://rea.tools/showcase/ctf/>
- Primary source: <https://github.com/morluto/rea/blob/808339f0b1cf3837445f392b5d5f1f362d64a27d/website/evidence/ctf-masked-squares.md>
- Catalog page: <https://awesomerea.org/resources/rea-ctf-case/>
- Record JSON: <https://awesomerea.org/resources/rea-ctf-case/record.json>
- Chinese version: [简体中文](https://awesomerea.org/zh/resources/rea-ctf-case/index.md)

## Requirements & limits

- **Prerequisites:** Upstream case: public DownUnderCTF 2023 challenge, REA 4.1.0 and Ghidra 12.1.4 on Linux x64.
- **Testing evidence:** Target hash and source revision are documented; author-reported execution.

## Primary sources

1. <https://github.com/morluto/rea/blob/808339f0b1cf3837445f392b5d5f1f362d64a27d/website/evidence/ctf-masked-squares.md>

## More in Native binaries

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## About this entry

The description was reviewed against primary sources.
Original editorial content: MIT. Linked projects, papers and assets retain their own rights and licenses.