05_PRACTICAL_REVERSE_ENG PORTAL
Week 4 Memory · Dual Sovereign Core (AR / EN)
⚡ BARE-METAL FILE HEADER DECODING & MAGIC NUMBERS
AYMAN ELMASRY
Computational Creative Director · AI Prompt Engineer
Founder of Ayman Elmasry LLC
🔒 ⚡ AEL Sovereign Seal (Active Master Verification)
{
  "ael_seal": "AEL CS Encyclopedia — © Ayman Elmasry",
  "owner": "Ayman Elmasry",
  "legal_entities": [
    "Ayman Elmasry LLC (UAE)",
    "Ayman Elmasry Advertising & Marketing (Egypt)"
  ],
  "syllabus_source": "Harvard CS50x 2026-2027",
  "domain": "Week 4 Memory: Bare-Metal File Header Decoding & Magic Numbers",
  "document_type": "05_Practical_Reverse_Eng",
  "methodology": "8-Stage Sub-Silicon Execution Paradigm",
  "system_version": "v3.0"
}

Practical Reverse Engineering: Bare-Metal Headers

Decoding JPEG Magic Numbers (Forensic Verification)

A legitimately formatted JPEG image file must universally initiate with a strict 4-byte hexadecimal header sequence: 0xFF, 0xD8, 0xFF. External file extensions can never be trusted. 

===================================================================================
             JPEG MAGIC NUMBER FORENSIC SIGNATURE MATRIX
===================================================================================

  [ BYTE 0 ]   :   0xFF  (1111 1111)
  [ BYTE 1 ]   :   0xD8  (1101 1000)
  [ BYTE 2 ]   :   0xFF  (1111 1111)
  [ BYTE 3 ]   :   0xE0 .. 0xEF  (Matches bitwise: (buffer[3] & 0xF0) == 0xE0)

===================================================================================

BITMAP Header Dissection (BMP Decoding Engine)

A bare-metal BMP file header comprises two strict C structs: BITMAPFILEHEADER (14 bytes) and BITMAPINFOHEADER (40 bytes). Uncompressed pixels are stored in reverse BGR byte order.

Forensic File Carving Protocols

When an OS deletes a file, it merely scrubs the base filesystem directory index, leaving data payloads intact. A file carving engine scans unindexed disk images for valid Magic Numbers to reconstruct lost assets.