单词本：unencumbered

因为非对称加解密计算量很大，对于那些资源有限的工业设备来说，可能负担不起。

NIST 的电网安全指南(The Smart Grid Interoperability Panel–Smart Grid Cybersecurity Committee 2014)就提到：

A trustworthy and unencumbered implementation of cryptography that is suitable (both computationally and resource-wise) for deployment in the smart grid would benefit all stakeholders in smart grid deployments.

这里， unencumbered 的意思是没障碍、没负担的意思。指南后面还提到：

The preconfigured SA class solution, for all but the smallest systems, is likely to be excessively costly, subject to human error, and encumbered with significant vulnerabilities due to the replication of so many credentials.

这里，encumbered 则是有负担的、有障碍的。

encumber 是个及物动词，意思是阻塞、妨碍、拖累。比如 You shouldn’t let those heavy books encumber you. 你不该让这些沉重的书拖累你的学习。

而 cumber 则是不及物动词，比如 He does’t want to cumber with anyone! 他不想拖累任何人。

cumber 可能最早源自拉丁语 cumulus ，堆积的意思。 cumulus 还是积云的意思。

References