DEAD Sector Merger

A small tool for HDD firmware-module repair. Compares two binary dumps of the same module (or system file) sector-by-sector and produces a clean merged copy by:

• Taking the good sector from whichever copy has it when only one is DEAD
• Zero-filling any sector that is DEAD in both copies
• Flagging conflicts where both copies are readable but differ — output is produced in two versions (prefer-A and prefer-B) so the operator can compare

A "DEAD" sector is a 512-byte sector entirely filled with the repeating pattern DE AD DE AD ... — the standard fill an imager writes when a sector can't be read off the platter.

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Run locally

pip install -r requirements.txt
streamlit run streamlit_app.py

Open the URL Streamlit prints (typically http://localhost:8501).

Deploy

This is a single-file Streamlit app — drop it on Streamlit Community Cloud, Hugging Face Spaces, or any host that runs streamlit run streamlit_app.py.

requirements.txt only needs streamlit; everything else is in the Python standard library (zipfile, re, io).

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Usage

1. Enter the password at the gate.
2. Upload two binary dumps. Three ways:
   • Drop a ZIP containing exactly two files
   • Pick two files at once in the multi-file uploader
   • Upload them separately into the File A / File B slots
3. When uploading as a pair or ZIP, the app auto-assigns A and B by filename pattern. The detection priority is:
   1. copy1 / copy2 (lower number = A)
   2. _a / _b suffix (case-insensitive)
   3. Common-prefix files differing only by a trailing number
   4. Lowest standalone digit anywhere in the filename
   5. Case-insensitive alphabetical fallback Use the Swap A ↔ B button if it guessed wrong.
4. Click Process Files.
5. Review the summary stats, download merged_preferA.bin and/or merged_preferB.bin, and inspect specific sectors in the hex viewer.

The hex viewer color-codes each sector by its status (match / recovered / zeroed / conflict). Conflict sectors highlight the bytes that actually differ between A and B in yellow.

Constraints

• Both files must be exactly the same size in bytes
• File size must be a multiple of 512 (sector-aligned)
• ZIPs must contain exactly two files (hidden files and __MACOSX/ metadata are ignored)
• All processing happens on the server hosting the Streamlit app — files are not persisted after the session ends

Files in this repo

• streamlit_app.py — the app
• requirements.txt — Python deps
• dead-sector-merger.html — standalone browser version (no server required; opens directly in any browser; client-side processing only)
• test_a.bin, test_b.bin — synthetic test fixtures (8 sectors each, exercising every code path)
• test_pair.zip — the same fixtures bundled into a ZIP renamed module_copy1.bin / module_copy2.bin to demo the pattern detection
• expected_preferA.bin, expected_preferB.bin — what the merged downloads should look like for the test fixtures (bytewise diff = 512 bytes, the one conflict sector)
• checksum-research.md — notes on which drive architectures use module checksums and where their algorithms are (or are not) documented

Password

The app is gated by a single shared password defined at the top of streamlit_app.py as the PASSWORD constant. To change it, edit the constant. For production use you may prefer to read it from st.secrets instead.

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Built for $300 Data Recovery.