Hacking the Xbox

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Hacking the Xbox: An Introduction to Reverse Engineering
word on who can or cannot run programs on the console, and hackers
cannot modify games to insert viruses, Trojan horses, or back doors.
Saved games are also sealed using encryption, and as a result, it is
nominally impossible to hack a game and cheat by patching the executable
or by jacking up your character stats.
Clearly, a pivotal issue in hacking the Xbox console is their implementation
of the digital signature system. The Xbox uses a SHA-1 hash with 2048-bit
RSA keys, making the chance of a successful brute force attack very, very slim.
Of course, the probability is zero if you never try, but the odds are stacked
against you (see the sidebar “Very Difficult Problems”). You’ll have better
luck trying to win the lottery. This is by no mistake; the discovery of the
private key would make game copying trivial and developers would not have
to pay royalties to Microsoft (legally, they may be obligated but there is no
technical reason preventing them). Given that this key is probably worth a
few billion dollars to Microsoft, it is quite likely that no single human
knows the full key, as rubber-hose (beatings) and green-paper (bribery)
cryptanalysis techniques tend to be quite effective on humans. (Do not
discount real “brute force” as a possibility if you are trying to protect an
extremely valuable secret!) Products such as BBN’s SignAssure certificate
authority management system ensure the physical security of high-value
keys and implement secret-sharing schemes that require multiple trusted
users to activate the machine.
As mentioned previously, there are a few known viable attacks against RSA,
but not all of them apply in the Xbox scenario, as they rely on groups of
users or require chosen-ciphertext. In addition, the list of weaknesses is
widely known and most implementations of digital signatures implement
the proper countermeasures to protect against such attacks.
The Rest of the Picture
An effective security system needs good key management, strong
protocols, and in the case of the Xbox, physical security in addition to
strong ciphers and hashes.
Key management is perhaps one of the most difficult system implementation
tasks that face any security architect. Ultimately, the decryption keys need
to go into the hands of a user. The user interface must be designed so
that the average user with minimum training does not accidentally leak
key information. As ciphers become stronger, the easiest path of attack is
increasingly through the user. Eavesdropping through surveillance videos,
social engineering, or even analyzing the pattern of sounds made by the
keyboard as a password is typed will probably yield more information per
unit effort about a passphrase than cryptanalysis. Public key cryptography
partially helps solve the problem of key distribution, but public key
fingerprints should be compared in person to rule out the possibility of
man-in-the-middle attacks. Public key cryptography also does not
prevent someone with physical access to the client machine from eavesdropping
on the decrypted output.