Ultra-low-cost True Randomness

Cryptocrat writes "Today I blogged about a new method for secure random sequence generation that is based on physical properties of hardware, but requires only hardware found on most computer systems: from standard PCs to RFID tags." Basically he's powercycling memory and looking at the default state of the bits, which surprisingly (to me anyway) is able to both to fingerprint systems, as well as generate a true random number. There also is a PDF Paper on the subject if you're interested in the concept.

Comments

Re:933245789124398

[BadAnalogyGuy]

23423483837223429723432891023478343589435892

You would expect that, you fucking pervert.

Oblig. XKCD

[IcedTeaisgood]

http://xkcd.com/221/

A VERY interesting idea...

[nweaver]

the true RNG properties rely on the fact that:

a: Many of the bits are sorta random, but physically random. So very biased coins, but true randomness.

b: With the right reduction function, you can turn a LOT (eg, 512 Kb) of cruddy random data to a small amount (128b-512b) of very high quality, well distributed random.

And the fingerprinting relies on the fact that:

a: Many other of the bits are physically random, but VERY VERY biased. So map where those are and record them and it is a very good fingerprint. And since it is all silicon process randomness going into that, it is pretty much a physically unclonable function.

Kevin Fu has some SMART grad students.

Our research group will answer questions soon...

[fubob]

We were surprised to suddenly get attention to this paper, but apparently Slashdot readers are watching the security seminar at UMass Amhest.

Anyhow, we will be answering questions in this thread. So if you have any questions, post them here and Dan Holcomb will get back to you as soon as he can.

Cheers,
-Kevin Fu

Re:Four

[ukatoton]

RTFA
There are 3 states the bits can fall into:

1. initially (almost) always 0
2. initially 0 or 1 with somewhat even probability
3. initially (almost) always 1

Using the bits that fall into category 2 to generate the number will result in a random number, as these are known to change randomly

since it is now known which bits will change with each power cycle, those bits can be used as a source of true randomness

Bits falling into the other two states are ignored for the random function and are used for the identification function.

Don't follow the hype. Does not apply to PC's.

[rpp3po]

The original paper is much better than CmdrTaco's quick conclusions.
The described method is ONLY for SRAM (statical RAM), no DRAM, no SDRAM. You can find this on RFID chips and in a CPU'S cache, not in RAM. As there is no way to access a CPU's cache uninitialized, I can't see why this should be useful.
If you have to modify a CPU first, to allow access to it's unitialized caches (think about all the unwanted implications), it's much cheaper to just give it a thermal diode and register to poll (as most modern CPU's already have).
After all the described method is just another way of collecting thermal noise. As RFID's are custom designs most of the time, also there it would be cheaper to just use a thermal diode.
The only application for this would be if you had to develop strong crypto for legacy RFID chips.
Slashdot stories get worse by the day.

Re:This is hardly random

[tlhIngan]

As an embedded engineer, I've encountered numerous cases where power cycling RAM did not alter the contents.

In fact, I've seen systems boot and run even after the power was cut for several seconds. Some types of SRAM and SDRAM have the ability to retain an (imperfect) memory image even at very low voltage levels. Sure, it's not guaranteed to be accurate by the manufacturer, but RAM "images" are a pretty well known phenomenon. In some cases, the contents of memory can be reconstructed even after the computer has been powered off and removed to a forensic laboratory.

This is not random at all. In fact, it's more likely to produce an easily exploitable RNG than anything else; I would not be at all surprised if the standard UNIX random number generator provided better security.

I've had this bite me, and exploited it.

It bit me when booting into Windows CE - you'd power cycle the thing, and the OS would boot with the old RAM disk you had - we'd gotten to the point where we'd have the bootloader wipe the kernel memory so the data structures were all corrupted by the time the OS was trying to decide between mounting the RAM disk (object store) and starting fresh. It turns out that the longer an image is unchanged in RAM, the more likely the cells woudl be biased such that if you cycle the power on them, they're more likely to lean towards the way they were before power was cut.

The time I exploited it, I didn't have any way of logging. Logging to serial port caused issues (timing-sensitive code), so I logged to memory (and no, I had no filesystem running, so I couldn't log to file). My trick was to simply log to a circular RAM buffer. When it crashed, I would just power cycle and dump the RAM buffer. Even though the data was fresh, it was enough to make out what my debug message was trying to say (almost always perfect). This was readable after a brief power cycle, and was still readable after turning power off for nearly a minute. The characters got corrupted, but since it was regular ASCII, you could still make out the words.

Old news - I have already been granted patents

[ironring]

This is a bit of old news. I have already authored and been granted several patents in this area.
6,906,962 Method for defining the initial state of static random access memory
6,828,561 Apparatus and method for detecting alpha particles
6,738,294 Electronic fingerprinting of semiconductor integrated circuits
I have several other ideas for application of this technology and would be happy to discuss if someone is interested.
Paul