Researchers Build True Random Number Generator From Carbon Nanotubes (ieee.org)

Wave723 writes: IEEE Spectrum reports on a true random number generator that was created with single-walled semiconducting carbon nanotubes. Researchers at Northwestern University printed a SRAM cell with special nanotube ink, and used it to generate random bits based on thermal noise. This method could be used to improve the security of flexible or printed electronics. From the report: "Once Mark Hersam, an expert in nanomaterials at Northwestern University, and his team had printed their SRAM cell, they needed to actually generate a string of random bits with it. To do this, they exploited a pair of inverters found in every SRAM cell. During normal functioning, the job of an inverter is to flip any input it is given to be the opposite, so from 0 to 1, or from 1 to 0. Typically, two inverters are lined up so the results of the first inverter are fed into the second. So, if the first inverter flips a 0 into a 1, the second inverter would take that result and flip it back into a 0. To manipulate this process, Hersam's group shut off power to the inverters and applied external voltages to force the inverters to both record 1s. Then, as soon as the SRAM cell was powered again and the external voltages were turned off, one inverter randomly switched its digit to be opposite its twin again. 'In other words, we put [the inverter] in a state where it's going to want to flip to either a 1 or 0,' Hersam says. Under these conditions, Hersam's group had no control over the actual nature of this switch, such as which inverter would flip, and whether that inverter would represent a 1 or a 0 when it did. Those factors hinged on a phenomenon thought to be truly random -- fluctuations in thermal noise, which is a type of atomic jitter intrinsic to circuits." Hersam and his team recently described their work in the journal Nano Letters.

Comments

Summary fail

[Wdi]

The random generator passed only 9 of 15 standard randomness tests of NIST. Not surprising - it is unlikely that the two inverter branches are identical to the atom level, and that is a prerequisite that the thermal noise has exactly equal chance of flipping either branch.

Re:Summary fail

[Togden]

If it were truly random, surely it would pass the tests at random, and so really we should be checking that it passes different tests each time, except on occasion when it doesn't.

Nice save

[physicsphairy]

Researcher 1: "Our nanotube project is outputting completely garbage data. I guess this means we can't publish."
Researcher 2: "Or... can we?"