Ring Oscillator-based Physically Unclonable Function (RO PUF) is widely concerned because of its simple structure and good properties. Unfortunately, in order to maintain high reliability, the traditional RO PUF can only extract 1 bit entropy by comparing the frequency's magnitude of two selected ring oscillators (ROs), which is far from enough, especially in PUF-based key generation scenarios. In this paper, we propose an efficient and concise RO PUF response generation scheme based on FPGA platform by using high-order difference method, which significantly improves the response generation rate and entropy extraction rate of an RO pair by the fine control of Programmable Delay Lines (PDLs) in Look-Up Tables (LUTs). In addition, we build loop delay models and conduct extensive experiments on Xilinx's 28nm FPGAs (Kintex-7, Virtex-7 and Zynq-7000) to prove the effectiveness of our scheme.

Flush based cache attacks have become a practical threat to data privacy and information security due to their advantages such as high accuracy and resolution. However, their accuracy and resolution still has room for improvement. In addition, although most of the attacks have been demonstrated on x86 processors, few of them have been executed on ARM devices. We propose a high accuracy, high resolution flush based cache attack, Flush+Time. This technique solves two important challenges for cache attacks on ARM: how to flush cache lines and how to achieve precise timing. Experiments show that Flush+Time increases accuracy from 95.1% of Flush+Reload, the most powerful general cache attack so far, to 99.3%. Flush+Time has a 30.5% higher resolution than Flush+Reload, but its execution time is only 0.59 times that of Spectre.

Key protection on mobile devices is attracting more attention with the rapid growth of mobile payment. There are many key protection methods proposed in academia from the following three aspects. The first is from algorithmic perspective, such as white-box cryptography. The second is from physical protection perspective, such as secure element (SE). The last is from key escrow perspective, such as cloud secure element (Cloud SE). The security of the white box cryptography has not yet reached an agreement in academia, and SE cannot defend against unknown side channel attacks in the future since it can hardly be updated. With regard to Cloud SE, the user has to totally trust the cloud, including the cloud provider, the cloud environment, etc. However, with the development of attack methods, the complete credibility of the cloud has gradually become an excessive requirement. In this paper, we propose KPaM, a low-cost and flexible key protection framework for mobile devices, which can mitigate the issues described above. The main idea of KPaM is inspired by emerging two-party computation algorithm. The private key is split into two parts, stored and used in the mobile device and the cloud respectively. The cloud does not store the complete key, so there is no need to worry about the abuse of the user's private key. On the mobile side, we get rid of SE and use TEE (trusted execution environment) to perform cryptographic operations and access control mechanism, which realizes the functions of secure storage and trust path. At last, we take SM2 algorithm as an example to validate KPaM and evaluate its security and efficiency.

SNOW 3G and ZUC are both the heart of secure algorithm sets in 3GPP LTE-Advanced, which is the potential candidate for 4G mobile broadband communication standard. In this paper, we optimize the implementation of the SNOW 3G and ZUC on FPGA, and also evaluate their performance. Our implementation of SNOW 3G reaches a little higher throughput than that of the best commercial IP core. Our optimized implementation of ZUC gives 40% performance improvement, compared with the best reported methods in terms of area-throughput ratio. Especially, compared with the ASIC implementation of ZUC in the most recent work in INDOCRYT 2011, the critical path of our architecture is 20% shorter than theirs. Our evaluation results show that both SNOW 3G and ZUC are flexible to balance different throughput with consumed area.