Information leakage through document redaction: Attacks and countermeasures

It has been recently demonstrated, in dramatic fashion, that sensitive information thought to be obliterated through the process of redaction can be successfully recovered via a combination of manual effort, document image analysis, and natural language processing techniques. In this paper, we examine what might be revealed through redaction, exploring how known methods might be employed to detect vestigial artifacts of the pre-redacted text. We discuss the process of redaction and circumstances under which sensitive information might leak, present an outline for experimental analyses of various approaches that could be used to recover redacted material, and describe a series of increasingly stringent countermeasures to address, and in some cases eliminate, the perceived threat