Hi, On So, 2016-06-18 at 10:44 -0400, Theodore Ts'o wrote: > On Fri, Jun 17, 2016 at 03:56:13PM +0200, David Jaša wrote: > > I was thinking along the lines that "almost every important package > > supports FreeBSD as well where they have to handle the condition so > > option to switch to Rather Break Than Generate Weak Keys would be nice" > > - but I didn't expect that systemd could be a roadblock here. :-/ > > It wasn't just systemd; it also broke OpenWRT and Ubuntu Quantal > systems from booting. > > > I was also thinking of little devices where OpenWRT or proprietary > > Linux-based systems run that ended up with predictable keys way too > > ofter (or as in OpenWRT's case, with cumbersome tutorials how to > > generate keys elsewhere). > > OpenWRT and other embedded devices (a) generally use a single master > oscillator to drive everything, and (b) often use RISC architectures > such as MIPS. > > Which means that arguments of the form ``the Intel L1 / L2 cache > architecture is ****soooo**** complicated that no human could possibly > figure out how they would affect timing calculations, and besides, my > generator passes FIPS 140-2 tests (never mind AES(NSA_KEY, CNTR++) this > also passes the FIPS 140-2 statistical tests)'' --- which I normally > have trouble believing --- are even harder for me to believe. > > At the end of the day, with these devices you really badly need a > hardware RNG. and this. It seems much easier to me to embed AES(NSA_KEY, CNTR++) logic directly to HW RNG compared to tweaking of every microarchitecture to make jitter/maxwell/havege return known numbers that are going to be mixed with other entropy anyway (won't they?). So if I put the bits together correctly, HW RNG helps getting more random numbers but itself is insufficient to ensure that random numbers are truly random... Cheers, David Jaša > We can't generate randomness out of thin air. The only > thing you really can do requires user space help, which is to generate > keys lazily, or as late as possible, so you can gather as much entropy > as you can --- and to feed in measurements from the WiFi (RSSI > measurements, MAC addresses seen, etc.) This won't help much if you > have an FBI van parked outside your house trying to carry out a > TEMPEST attack, but hopefully it provides some protection against a > remote attacker who isn't try to carry out an on-premises attack. > > Cheers, > > - 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
