On Fri, Feb 08, 2013 at 11:04:54PM +0100, Stephan Mueller wrote: > * an array of statistical test suites pass the output of the entropy > collector > (again, the output is not mangled with cryptography) You're not mangling the output with cryptography, but you are doing some mangling in jitterentropy_cpu_jitter(). So let's be clear about what the heart of your entropy source is: You're getting the nanoseconds out of clock_gettime(CLOCK_REALTIME), and then mixing it using XOR and a ROL(3) into a 64-bit buffer, and interspersing the calls to clock_gettime() with schedule(). So what a code breaker at the NSA would probably try to do first is to measure is whether there is any kind of bias or non-entropy in the nanoseconds returned by CLOCK_REALTIME after calls to schedule(). If they can find any kind of bias, they can use that to calculate what kind of patterns or non-random bits might end up showing up after you do your non-cryptographic mangling. For that reasons, what I would suggest doing first is generate a series of outputs of jitterentropy_get_nstime() followed by schedule(). Look and see if there is any pattern. That's the problem with the FIPS 140-2 tests. Passing those tests are necessary, but *NOT* sufficient to prove that you have a good cryptographic generator. Even the tiniest amount of post-processing, even if they aren't cryptographic, can result in an utterly predictable series of numbers to pass the FIPS 140-2 tests. Regards, - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-crypto" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
