# Project Frankenstein: Vol XXIX

### GCC-4241N Security State Machine & Hardware Proxies

Executive Summary:
This document outlines the complete structural map of the GCC-4241N's security mechanisms. Through differential memory analysis and assembly execution tracing, we have identified the Master SCSI Dispatcher, defeated RAM obfuscation techniques, and mapped the hardware proxies responsible for engaging the DVD descrambler and authentication flags. This intelligence forms the foundation for injecting the proprietary Xbox GDR-8050L authentication logic.

## 1. Memory Mirroring Architecture

The MN10300 processor implementation in this drive utilizes physical SRAM mirroring. The silicon maps a small physical address space across a much larger virtual window. This means that a memory read or write to `0x171F` or `0x3F1F` is physically accessing the identical cell at base address `0x071F`.

This architectural quirk initially produced false positives in differential scans. By focusing purely on the lowest base offsets, the true state machine variables were isolated.

## 2. RAM Execution & Obfuscation

The firmware employs a defense-in-depth strategy to hide cryptographic routines. Rather than executing directly from ROM, the system bootloader utilizes an aliased ROM mapping (`0xB01E0000`) to dynamically copy the security payload into RAM during initialization.

    40030287:    fc de 00 3a     mov     -1340261888,a2   ; A2 = 0xB01D3A00 (RAM Dest)
    40030290:    f1 e8           mov     d2,a0            ; A0 = Calculated Size
    40030299:    fc cd 08 78     mov     -1340114936,d1   ; D1 = 0xB01F7808 (ROM Source)
    4003029f:    cd 7e 7c c0     call    0x40037f1d       ; Execute memcpy()

The target payload executes from RAM at `0xB01D3A00`, but static analysis requires extracting the unencrypted source bytes from ROM address `0x40017808`.

## 3. The Hardware Proxies (Gatekeepers)

The firmware prevents tampering by abstracting direct memory writes to security registers. Instead of flipping bits directly, the state machine utilizes two "proxy" sequencer functions that interface with the internal ASIC to commit state changes.

### 3.1 The Authentication Flag (0x0662)

The cryptographic validation subroutine determines if a valid challenge response has been met. If successful, it calculates a 4-byte checksum, loads the authentication flag address (`0x0662`), and calls the proxy function at `0x4000c485`.

    40017813:    2c 62 06        mov     1634,d0          ; Load 0x0662
    40017816:    fc cd b0 d8     mov     55472,d1         ; Load State Buffer
    4001781a:    00 00
    4001781c:    dd 69 4c ff     call    0x4000c485       ; Execute State Commit

### 3.2 The Descrambler Enable Register (0x06EC)

Similarly, when Mode Select command `0x15` dictates a change in descrambler status, the jump table routes execution to a block that clears adjacent state values, writes the enable bit, and commits the change via the hardware sequencer proxy at `0x400110a2`.

    4001cd68:    00              clr     d0
    4001cd69:    03 e8 06        movhu   d0,(0x6e8)       ; Clear adjacent state
    4001cd6c:    03 ea 06        movhu   d0,(0x6ea)
    4001cd6f:    80 01           mov     1,d0             ; Enable bit (1)
    4001cd71:    02 ec 06        movbu   d0,(0x6ec)       ; Target Descrambler Reg
    4001cd74:    dd 2e 43 ff     call    0x400110a2       ; Execute ASIC Commit

## 4. Application Strategy for Injection

To successfully convert the GCC-4241N to accept original Xbox authentication, the following injection strategy must be employed:

1. Hook the Dispatcher: Intercept SCSI commands `0xAD` and `0x55` at the primary switchboard (`0x400011ef`) and redirect them to a custom memory block.
2. Inject Cryptography: Port the proprietary Xbox SHA1/RC4 challenge-response algorithm from the GDR-8050L firmware into the GCC-4241N.
3. Call Native Proxies: Upon successful calculation of the challenge response, the injected code must manually invoke `0x4000c485` to validate the Auth Flag and `0x400110a2` to engage the Descrambler.