The Null Device

Security through randomness

Bruce Schneier has a post about an interesting way to beat buffer overrun attacks:
Fortunately, buffer-overflow attacks have a weakness: the intruder must know precisely what part of the computer's memory to target. In 1996, Forrest realised that these attacks could be foiled by scrambling the way a program uses a computer's memory. When you launch a program, the operating system normally allocates the same locations in a computer's random access memory (RAM) each time. Forrest wondered whether she could rewrite the operating system to force the program to use different memory locations that are picked randomly every time, thus flummoxing buffer-overflow attacks.
Memory scrambling isn't the only way to add diversity to operating systems. Even more sophisticated techniques are in the works. Forrest has tried altering "instruction sets", commands that programs use to communicate with a computer's hardware, such as its processor chip or memory.
This produces an elegant form of protection. If an attacker manages to insert malicious code into a running program, that code will also be decrypted by the translator when it is passed to the hardware. However, since the attacker's code is not encrypted in the first place, the decryption process turns it into digital gibberish so the computer hardware cannot understand it.

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