Exploiting power supply ramp rate for calibrating cell strength in SRAM PUFs
Exploiting power supply ramp rate for calibrating cell strength in SRAM PUFs
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利用电源斜坡速率来校准 SRAM PUF 中的单元强度
DOI：
10.1109/latw.2018.8349685
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发表时间：
2018
期刊：
影响因子：
--
通讯作者：
A. Chatterjee
中科院分区：
文献类型：
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作者：
Wendong Wang;A. Singh;Ujjwal Guin;A. Chatterjee
SRAM阵列对于物理上无倾斜的功能（PUF）特别有吸引力，因为SRAM阵列的每个制造副本在最初供电时都会显示出不同的内存模式。这是由于制造过程变化中单个存储单元中设备参数的随机差异。然而，在预期的工作电压和温度范围内，SRAM PUF响应的不稳定以及环境噪声和随着时间的变化的衰老是一个挑战。最近的建议旨在确定SRAM，最健壮或最强细胞中所有细胞的子集，并仅使用这些细胞来构建PUF。但是，在早期的工作中，SRAM供电的方式在很大程度上被忽略了。我们表明，SRAM电力状态在很大程度上取决于电源坡道的速率和方向。在不同的电力场景下获得了截然不同的电力状态。此外，在不同的坡道速率和方向下分析加电状态可以提供相当大的洞察力，以了解每个单个单元中的晶体管对不匹配，甚至不匹配的程度。由于这样的阈值电压不匹配是细胞电源偏置的关键，因此我们最终展示了如何利用此类实验以可靠地识别SRAM中最强大的强细胞用于PUF。可以期望这些单元在各种操作条件，噪声和设备降解范围内生成可靠的密钥，以实现加密操作。
SRAM arrays are particularly attractive for use as physically unclonable functions (PUFs) because each manufactured copy of an SRAM array displays a different memory pattern when initially powered-on. This is due to random differences in device parameters in individual memory cells from manufacturing process variations. However, instability in the SRAM PUF response over the expected range of operating voltages and temperature, as well as environmental noise and aging degradation over time, is a challenge. Recent proposals aim at identifying a subset of all the cells in an SRAM, the most robust or strong cells, and using only these to construct a PUF. However, the manner in which the SRAM is powered up has been largely ignored in earlier work. We show that the SRAM power-up state is strongly dependent on the power supply ramp rate and direction; very different power-up states are obtained under different power-on scenarios. Furthermore, analyzing the power-up states under different ramp rates and directions can provide considerable insight into which transistor pairs in each individual cell are mismatched, and even the extent of the mismatch. Since such threshold voltage mismatch is key to cell power-on bias, we finally show how such experiments can be exploited to reliably identify the most robust strong cells in SRAMs for use in PUFs. These cells can be expected to generating reliable keys for cryptographic operations across a wide range of operating conditions, noise and device degradation.