The new Xbox dashboard update also brings a few other surprises.



As you may know, Microsoft recently a new kernel update (2.0.15572.0).
Now, it looks like they also added a new key to their hash calculation for the rc4 key. So, DON'T UPDATE WITHOUT BACKING UP FIRST

That's right, seems that with the new recently released XBOX Dashboard update, Microsoft had some other suprises prepared.

According to Team-Xecuter, they basically killed the XOR Hack, so you shouldn't update to 15*** without backing up first!

Here's their explanation:

With the new 15*** update, M$ has added a new key to their hash calculation for the rc4 key. It's basically just the first 16 bytes of the header, which include the version number, entrypoint, and size. These are all per-CB, per-version, so we cannot take a keystream from a 15*** CBB and use it to make a 14*** CB because the CBA on 14*** is unable to calculate the rc4 key no matter what we change.

What this means:
In order to RGH2 an xbox with 15***, you need either:

1) The cpu_key

2) A previous exploitable dump from the SAME XBOX. Must fit one of the following:
- Phats: 14717, 14719
- Slims: 13146, 13599, 14699, 14717, 14719

Older dumps will NOT WORK with RGH2/RGH3 !

DO NOT UPDATE TO 15*** WITHOUT BACKING UP FIRST!

What do we do now:
We are looking into ways of exploiting the rc4.

To make it clear, the new way of generating the CBB decryption rc4 key is as follows:

Secret = CBA[0x10:0x20]
Digest = CBB[0x10:0x20] + CPU_Key + CBA[0:6] + 0×0000 + CBA[8:0x10]

def decrypt_CB_Cpu(CB):
assert cpukey
secret = CB_A[0x10:0x20]
h = hmac.new(secret,None, sha);
h.update(CB[0x10:0x20]);
h.update(cpukey);

v = struct.unpack(">h", CB_A[0x6:0x8])[0]
print " * checking flag: %X" % v
if( v & 0x1000):
print " ** Using new encryption scheme"
h.update(CB_A[0:0x6] + "\x00\x00" + CB_A[8:0x10]);

key = h.digest()[0:0x10]
CB = CB[0:0x10] +key+ RC4.new(key).decrypt(CB[0x20:])
return CB
So, there you go. You are now warned, and if you already updated, wait patiently!

NEWS SOURCE #1: News Article #3029 (via) EurAsia
NEWS SOURCE #2: How M$ killed the XOR hack (via) Team-Xecuter

Our thanks to 'Gauss' for this news item!