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Over the last decade, advancements in performance and efficiency of portable computing devices have allowed them to provide much of the functionality previously restricted to larger computers. Instant communication, GPS navigation, remote banking, and even online shopping are only a few of the activities that can be performed from almost anywhere. However, these conveniences may come at the cost of physical security since portable devices are often operated in a public environment where there is a possibility of being physically exposed or obtained by untrustworthy users. While it is a common practice to secure the data that is transferred from one point to another, the contents of system memory often go unprotected. When physical access to a device is attained, this so called ``data-at-rest" can be exploited to reveal private information. Emails, GPS location data, financial transactions, etc. could be harmful if revealed to the wrong party. This thesis investigates the design trade-offs of obscuring data stored within low latency memory on an embedded device. This was achieved by implementing a parameterizable system based on the keystream cache concept. While this solution could be implemented for almost any embedded system, the design was evaluated using reconfigurable hardware in order to reduce development costs. A prototype was built and tested on an Altera FPGA development board where parameters of the architecture were varied to find a solution that reduced performance overhead, while minimizing hardware usage. The resulting application benchmarks show as little as 1% performance overhead while using minimal hardware resources.