CCI Reverse-Engineering & Validation Protocol

Project: Forza Motorsport | Platform: Xbox Original

01. Baseline Image Acquisition

Requirement: Establish a bit-perfect reference point.

Utilize ImgBurn or Xbox Backup Creator to generate a 1:1 Redump-verified ISO. This serves as the control variable for all binary comparisons.

Redump Hash: 4054a0568d49fb1224078ed1d1d7cab59287a8d5

Redump Trimmed Hash: de4e9780e8b704763a9ee694c1e4652c6d19b654

02. Variable Isolation (Repackinator)

Configure Repackinator to produce two distinct intermediate outputs to separate the scrubbing logic from the compression stage.

Output Name	Settings Configuration	Analytical Objective
Image A (Scrubbed ISO)	Enable: `Scrub` \| Disable: `Compress`	Isolates the sector-zeroing algorithm.
Image B (Final CCI)	Enable: `Scrub` \| Enable: `Compress`	Final production format for testing.

03. Differential Analysis & Verification

3.1 Compression Integrity

Decompress Image B (.cci) using a standard LZ4 command-line tool:

lz4 -d Forza.cci output_decompressed.iso

Validation: Perform a SHA-256 hash comparison between output_decompressed.iso and Image A. A match confirms CCI is an LZ4 stream of the scrubbed data.

04. CCI Header Specification

The first 32 bytes (0x00 - 0x1F) of a .cci file contain the Repackinator header. Open Image B in HxD to verify these fields:

Offset(h) 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F 00000000 43 43 49 00 01 00 00 00 [Block Size] [Total Size] ^ MAGIC ^ VER ^ 4 bytes ^ 8 bytes

Magic (00-03): Always 43 43 49 00 ("CCI\0").
Version (04-07): Typically 01 00 00 00 for current Repackinator builds.
Block Size (08-0B): The chunk size used for LZ4 compression (standard is 128KB).
Uncompressed Size (0C-13): Total size of the original scrubbed ISO in bytes.

05. Visual Hex Analysis (HxD)

Step 1: Open Baseline.iso and ImageA.iso in HxD.
Step 2: Press Ctrl+K to initialize comparison.
Step 3: Use F6 to identify offsets where random data in the Baseline becomes 0x00 in Image A.

06. Automated Verification Script

# CCI Integrity Verification Script
$ScrubbedISO = "ImageA.iso"
$DecompressedCCI = "output_decompressed.iso"

$HashA = (Get-FileHash $ScrubbedISO -Algorithm SHA256).Hash
$HashB = (Get-FileHash $DecompressedCCI -Algorithm SHA256).Hash

if ($HashA -eq $HashB) {
    Write-Host "SUCCESS: Bit-identical match confirmed." -ForegroundColor Green
} else {
    Write-Host "FAILURE: Hashes do not match." -ForegroundColor Red
}
        

Executive Summary: This protocol provides empirical proof of the CCI file structure: a specific metadata header, followed by a proprietary scrubbing pass, wrapped in industry-standard LZ4 compression.