Tom Butcher
8f2d3a2489
- Created .gitignore to exclude build artifacts and dependencies. - Added package.json and package-lock.json for project dependencies and scripts. - Included pnpm workspace configuration for managing packages. - Implemented TypeScript configuration in tsconfig.json. - Added README.md with project description and usage instructions. - Introduced native code for DES encryption and decryption in C/C++. - Created initial decoded data structure for handling scan results. - Established basic file structure for decoded outputs and native builds.
68 lines
3.2 KiB
Markdown
68 lines
3.2 KiB
Markdown
# Decoded Pectus Clinic torso scan
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Source: `Pectus Clinic - Butcher, Thomas - Torso - Original 20181023, 165650.med`
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## What this file is
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This is a **TechMed 3D** proprietary `.med` scan (same family as `.iMed` from 3DsizeMe / My3DsizeMe).
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The filename and date match **Pectus Scan**, TechMed’s white-label iPad app for Pectus Services (App Store id 1435160086, first shipped 8 October 2018). This capture is from **23 October 2018, 16:56:50** — an original torso scan of **Thomas Butcher**, branded under **Pectus Clinic**.
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Capture hardware is an **Occipital Structure Sensor** on an iPad (structured-light surface scan, no X-ray/CT dose). Pectus Services then measured these files in their **T-Scan** tool to plan a T-Joe brace.
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Official open exports from MSoft / MSoft+ are STL, OBJ, PLY, VRML, ASCII, and AOP. This `.med` is the locked working copy, not those exports.
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## Patient / scan metadata (from the filename)
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| Field | Value |
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| --- | --- |
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| Practice / app brand | Pectus Clinic |
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| Patient | Butcher, Thomas |
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| Body part | Torso |
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| Scan type | Original |
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| Timestamp | 2018-10-23 16:56:50 |
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TechMed names files:
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`{Practice} - {Last}, {First} - {BodyPart} - {ScanType} {YYYYMMDD}, {HHMMSS}.med`
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## Binary layout
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Total size: **756,064 bytes**.
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| Offset | Length | Contents |
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| ---: | ---: | --- |
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| 0 | 565,512 | Encrypted payload (mesh and other records) |
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| 565,512 | 8 | Encrypted zero / fill block `7c1cddebb73720e0` |
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| 565,520 | 128 | Encrypted trailer (16 blocks; two identical) |
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| 565,648 | 190,352 | Encrypted zero padding (23,794 × the same 8-byte block) |
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| 756,000 | 64 | Raw zeros, not encrypted |
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The repeating tail is the giveaway: an **8-byte block cipher in ECB mode** encrypting a large preallocated zero buffer. AES is ruled out (16-byte blocks would not produce two identical 8-byte halves). XOR with that block does not reveal STL/OBJ/PLY/XML/JPEG/PNG.
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A size that fits the buffer:
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- **23,563 × 24-byte vertices** (position + normal) used
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- **31,500 × 24-byte slots** allocated (= 756,000 bytes)
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That is a plausible Structure Sensor torso cloud/mesh. Photos and landmark/measurement fields that 3DsizeMe normally stores would sit in the same encrypted payload.
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## What could not be recovered from the file alone
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The mesh coordinates, faces, colour, photos, and any in-file measurements are behind a vendor key that is not stored in the file. Common TechMed / Pectus / MSoft passwords and derived DES/3DES/Blowfish/CAST/TEA keys were tried against the known `E(0) = 7c1cddebb73720e0` pair; none matched.
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To get an open 3D file you need one of:
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1. **MSoft** (Qwadra / TechMed) — File → Save As → STL / OBJ / PLY. Pay-per-scan tokens exist if you do not have a licence.
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2. **Pectus Scan / 3DsizeMe / MSoft+** on the original iPad workflow, if it can re-open this `.med` and export.
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3. **Pectus Services T-Scan** or the clinic that took the scan — ask them to re-export STL/OBJ.
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Contacts: support@techmed3d.com, info@pectusservices.com.
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## Files written here
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- `metadata.json` — identity, software, hashes
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- `format_layout.json` — region map and cipher notes
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- `header_64b.hex.txt` — first 64 ciphertext bytes
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- `trailer_128b.hex.txt` — 128-byte trailer dump
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