The Implementation Of TPM RNG Module

In order to develop trusted computing technology, TCG(Trusted Computing Group)defined TPM(Trusted Platform Module), which can provide safety storage and encryption function. This module is one microcontroller based on TCG industry standard. This controller is used to store password, digital certificate and cipher keys, and provides security certification, encryption and network connection service.As one of the main modules of TPM, RNG produces seed data for cipher, decipherment and key generation. It provides the internal random source for TPM, and TPM uses these random values for nonces, key generation and randomness in signatures.The requirement of high quality random numbers grows day by day, which results in true random number generator takes great attentions; And the appearance and development of system on a chip needs the realization of on-chip random number generator. Considering the two facts, this paper comes up with a new method of random number generator based on the noise source of Phase Locked Loop(PLL). The method can provide good properties: true randomness and easy to implementation and system integration.This method has three significant merits: (1)source of noise derives from physic phenomenon-jitter of PLL instead of free-running oscillator; 2) the primary data are processed by a won Neumann corrector, which removes the bias and improves the randomness of the data; 3)digital post-processing introduces LFSR and CASR arithmetic, which can better the statistic property of output of the random number generator, and assure that the generator possess true randomness and have a stable output of random numbers.In this paper, we have proposed a new method based on jitter of PLL and completed the design and test of the true random number generator. Furthermore, we get a conclusion about the properties of the generator by analyzing the statistic test results of the random outputs.It is an experiment of realizing random number generator based on PLL. The results can be used by TPM and referred by developers of high-quality random number generator.