Category Archives: entropy

Entropy and The Arduino: When Clock Jitter is Useful

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What do you do, when you need a random number in your programming? The chances are that you reach for your environment’s function to do the job, usually something like rand() or similar. This returns the required number, and you go happily on your way.

Except of course the reality isn’t quite that simple, and as many of you will know it all comes down to the level of randomness that you require. The simplest way to generate a random number in software is through a pseudo-random number generator, or PRNG. If you prefer to think in hardware terms, the …read more

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VU#817544: Windows 8 and later fail to properly randomize all applications if system-wide mandatory ASLR is enabled via EMET or Windows Defender Exploit Guard

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Microsoft Windows 8 introduced a change in how system-wide mandatory ASLR is implemented. This change requires system-wide bottom-up ASLR to be enabled for mandatory ASLR to receive entropy. Tools that enable system-wide ASLR without also setting bottom-up ASLR will fail to properly randomize executables that do not opt in to ASLR. Continue reading VU#817544: Windows 8 and later fail to properly randomize all applications if system-wide mandatory ASLR is enabled via EMET or Windows Defender Exploit Guard→

VU#817544: Windows 8 and later fail to properly randomize every application if system-wide mandatory ASLR is enabled via EMET or Windows Defender Exploit Guard

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Microsoft Windows 8 introduced a change in how system-wide mandatory ASLR is implemented. This change requires system-wide bottom-up ASLR to be enabled for mandatory ASLR to receive entropy. Tools that enable system-wide ASLR without also setting bottom-up ASLR will fail to properly randomize executables that do not opt in to ASLR. Continue reading VU#817544: Windows 8 and later fail to properly randomize every application if system-wide mandatory ASLR is enabled via EMET or Windows Defender Exploit Guard→

What is Entropy and How Do I Get More of It?

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Let’s start off with one of my favorite quotes from John von Neumann: “Any one who considers arithmetical methods of producing random digits is, of course, in a state of sin. For, as has been pointed out several times, there is no such thing as a random number — there are only methods to produce random numbers, and a strict arithmetic procedure of course is not such a method.”

What von Neumann is getting at is that the “pseudo” in pseudorandom number generator (PRNG) is really a synonym for “not at all”. Granted, if you come in the middle of …read more

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