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Method and System for Enhancing Randomness and Increasing Bit Generation Rate in Hardware True Random Number Generator

IP.com Disclosure Number: IPCOM000248435D
Publication Date: 2016-Nov-29
Document File: 3 page(s) / 82K

Publishing Venue

The IP.com Prior Art Database

Abstract

A method and system is disclosed for enhancing the randomness by introducing extra jitter in the ring oscillator (ROSC) and increasing the bit generation rate of a true random number generator. The method and system provides a direct power supply noise injection scheme using a simple noise injection circuit to generate the power supply noise (PSN) and the direct PSN injection scheme is placed in a feedback loop which generates PSN of ROSCs by applying the random bit-streams and ROSC outputs to control the peak current of PSN randomly.

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Method and System for Enhancing Randomness and Increasing Bit Generation Rate in Hardware True Random Number Generator

High-quality random number generation is essential for security applications and hardware true random number generators (TRNG) exploiting physical statistical phenomena have been explored. Ring oscillator (ROSC) based TRNG, which harvests the jitter of the oscillator as the random source, is one of the popular circuits for generating truly random numbers.

The random period jitter of the oscillating signal comes from internal noises, such as, but not limited to, thermal noise, shot noise and random telegraph noise. Larger jitter generates output bit-streams with higher randomness and achieves a shorter jitter accumulation time. Although the ROSC-based TRNG can be easily fabricated with complementary metal-oxide semiconductor (CMOS) standard cells, the amount of internal noises for the source of the jitter is so small that a highly random bit-stream cannot be generated and also the jitter accumulation takes a long time. If the TRNG is read in succession too quickly to achieve a high bit rate, the ROSC exhibits highly predictable behavior that the distribution of 0s and 1s is skewed and the quality of randomness in the bit stream is low. Hence, extra jitter in the ROSC helps to enhance the randomness and increase the bit generation rate of ROSC-based TRNG.

Disclosed is a method and system for enhancing the randomness by introducing extra

jitter in the ROSC and increasing the bit generation rate of TRNG. The method and

system provides a direct power supply noise injection scheme using a simple noise injection circuit which has transistors connected between the power supply VDD of ROSCs and Ground GND to generate the power supply noise (PSN). The direct PSN injection scheme is placed in a feedback loop which generates PSN of ROSCs by applying the random bit-streams and ROSC outputs to control the peak current of PSN randomly.

Thus, random PSN is provided to ROSCs and the jitter in ROSCs is increased to enhance the randomness and increase the bit generation rate, with a small area overhead using a few transistors and AND gates.

FIG. 1 illustrates a block diagram of an example of a TRNG based on an array of 64 ring oscillators (ROSCs).

Figure 1

1


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As illustrated in FIG. 1, within ROSCs positioned next to one another, the ROSCs operate at different high frequencies, respectively, such that no two frequencies are harmonically related. That is, the ROSCs are independent of each other, and no integer multiple exists between the frequencies of any two ROSCs. By using ROSCs

with frequencies that are not harmonically related, the ROSCs may be housed in close proximity with one another without exhibiting injection locking effects that reduce randomness.

The output of each ROSC feeds into a multiple-level latch and the multiple-level latch includes two stages of 64 bit registers, where a digital bit representing each...