Widevine L1 – Extracting Keybox from eMMC Dump (MSTAR Devices)

This guide explains how to identify and extract a Widevine L1 keybox from an eMMC dump, commonly found on MSTAR-based TVs and set-top boxes.

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📦 What You Need

• An eMMC dump (usually the largest file)
• Windows / Linux / macOS
• Hex editor or CLI tools:
  • strings
  • grep
  • xxd
• Provisioning script (can be used with VT)
• Basic understanding of DRM / Widevine flows

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2️⃣ Identifying the Correct eMMC Dump

✔ File Size

• Usually 4–8 GB
• Sometimes 15 GB+ (TV models)

➡️ Always pick the largest dump file

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✔ Detecting MSTAR Devices

Open the dump and check the beginning.

If it starts with: MBOOT

➡️ The device is using an MSTAR SoC
(common for TVs and set-top boxes)

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3️⃣ Locating the Widevine Keybox

❌ What Is NOT the Keybox

Ignore files or blocks like:

• bgroupcert.dat
• zgpriv.dat
• Dumps containing many MSTAR_SECURE blocks

➡️ Most of these are garbage / unrelated

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✅ How to Spot the Real Widevine Keybox

Search inside the dump for: MSTAR_SECURE

🔑 Key Insight: LENGTH MATTERS

A real Widevine keybox usually contains:

• ~6 lines of HEX data immediately after MSTAR_SECURE

Examples

3–4 lines ❌ Not a keybox Very large data ❌ Not a keybox ~6 lines ✅ Likely the real keybox

This is how experienced people recognize it instantly.

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4️⃣ build.prop — Why It’s Needed

build.prop is used to generate:

device_client_id_blob Search in the dump for: ro.build.fingerprint=

📋 Required Properties Mapping

device_client_id field build.prop property company_name ro.product.manufacturer model_name ro.product.model architecture_name ro.product.cpu.abi device_name ro.product.device product_name ro.product.name build_info ro.build.fingerprint

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⚠️ If build.prop Is Missing

• L1 will still work
• Metadata will be generic
• Lifetime remains unchanged (≈ 5 hours)

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🔐 MSTAR AES KEY

0007FF4154534D92FC55AA0FFF0110E0

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💬 Support & Discussion

Questions, suggestions, fixes, or issues:

👉 DRMLab Discord Server
https://discord.gg/bexEz5KypW

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🛠 Tools & Scripts

🔗 https://git.drmlab.io

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⚠️ Disclaimer

This information is provided for educational and research purposes only.
You are responsible for how you use it.