Project Frankenstein: Volume X

SHA1 & RC4 Cryptographic Engine Analysis

This volume provides a deep-dive analysis of the authentication routines extracted from the GDR-8050L donor. It details the mathematical flow, register usage, and memory requirements for the SHA1 and RC4 engines as they are ported to the GCC-4241N RAM Cave [cite: User Summary, GDR-8050L_Donor_Specification.html, Project_Frankenstein_Vol_VI_Addendum.html].

1. The SHA1 Hashing Engine

The SHA1 engine is the core of the console challenge response. It processes the 20-byte host challenge to generate a unique digest [cite: GDR-8050L_Donor_Specification.html, 129_perfect_trampoline_v18.py].

Metric	GDR-8050L Donor Value	Hybrid Payload Target
Routine Entry	`0x90008847` [cite: GDR-8050L_Donor_Specification.html]	`0x40008500` [cite: Project_Frankenstein_Vol_VI_Addendum.html]
Context Buffer	SRAM `0x4100` [cite: Project_Frankenstein_Vol_VI_Addendum.html]	DRAM `0x10CC0100` (Recommended) [cite: Project_Frankenstein_Vol_VI_Addendum.html]
Input Buffer	SDRAM `0x10C80000` [cite: 129_perfect_trampoline_v18.py]	SDRAM `0x10C80000` [cite: Project_Frankenstein_Vol_VI_Addendum.html]

Algorithm Lifecycle (MN103S)

Initialization: State variables (H0-H4) are set to standard SHA1 magic constants (e.g., 0x67452301).
Update: The 20-byte challenge from the console is padded and expanded into a 64-byte block.
Compression: The core loop executes 80 rounds of bitwise operations (AND, OR, XOR, ROTL) [cite: User Summary].
Finalization: The final 160-bit (20-byte) hash is written to the Response Context at 0x10C80014 [cite: Project_Frankenstein_Vol_VI_Addendum.html].

2. The RC4 Stream Cipher

RC4 is used to encrypt the communications channel between the drive and the console kernel once the initial hash is verified [cite: User Summary, GDR-8050L_Donor_Specification.html].

Feature	Location / Value
RC4 Logic Entry	`0x90008852` [cite: GDR-8050L_Donor_Specification.html]
S-Box Buffer	SRAM `0x4200` [cite: Project_Frankenstein_Vol_VI_Addendum.html]
Key Length	Typically 128-bit (16 bytes) or 160-bit (20 bytes) depending on game [cite: User Summary].

KSA (Key Scheduling Algorithm) Logic

The MN103S routine at 0x90008852 initializes a 256-byte S-Box permutation based on the session key. The S-Box is stored in internal SRAM for low-latency access during streaming [cite: GDR-8050L_Donor_Specification.html, Project_Frankenstein_Vol_VI_Addendum.html].

3. Integrated Handshake Flow

During the security handshake, the payload executes the following combined routine [cite: 129_perfect_trampoline_v18.py]:

; Pseudo-Code for Handshake Routine
1. Load Challenge from DRAM 0x10C80000
2. Call SHA1_Engine(0x40008500)
3. Call RC4_Initialize(Key = SHA1_Output)
4. Encrypt Security Sector Mirror (0x10C80040)
5. Signal "Ready" to Host via SRAM 0x2CC

4. Register Utilization (MN103S Calling Convention)

When calling these ported routines from your xbox_hybrid_payload.s, adhere to the 8050L register map to avoid corruption [cite: User Summary].

d0: Input data byte / XOR working register.
d1: Loop counter / bit-rotation offset.
a0: Pointer to Input Data (Challenge).
a1: Pointer to Working Context (SRAM Buffers).