Abstract
Key generation is one of the essential components to secure Android devices. Generating a key needs random numbers. In order to acquire high-quality random numbers, a noise source with high-entropy is required. In this paper, we analyze the process scheduling information of Android system, and find that the rules of the PID calling order reflect the change of interruption times. A sequence of time t, which is required to increase the same number of interruptions, follows the negative exponential distribution. The sequence is a Poisson stream that owns a memoryless property, that is, each value of the sequence is only related to adjacent values. So, the increased number of interruption times during the identical time can be regarded as a noise source. Random numbers can be generated by preprocessing the noise source information, quantization and coding. Our experimental results show that random numbers with higher entropy can be obtained with mean non-uniform quantization, sampling per 1ms and suppressing the running of the ksoftirqdr process.