{"id":14170,"date":"2020-12-22T18:40:23","date_gmt":"2020-12-22T23:40:23","guid":{"rendered":"http:\/\/www.iri.com\/blog\/?p=14170"},"modified":"2025-04-21T08:23:54","modified_gmt":"2025-04-21T12:23:54","slug":"masking-pdfs-and-images","status":"publish","type":"post","link":"https:\/\/www.iri.com\/blog\/data-protection\/masking-pdfs-and-images\/","title":{"rendered":"Masking PII in PDF & Image Files"},"content":{"rendered":"

IRI DarkShield<\/span><\/a> can search for, and mask, personally identifiable information (PII) and other sensitive data in many different file types, documents and databases on-premise or in the cloud. Among the file types supported are those in PDF and image formats, which are the focus of this article. Note that DarkShield can now also find and redact signatures in these sources as well<\/a>.<\/span><\/p>\n

As with other document types, DarkShield supports sensitive data discovery and protection in PDFs and images using masking functions specified as rules during data classification<\/a> in IRI Workbench. These <\/span>data masking <\/span>functions<\/span><\/a> include, but are not limited to, hashing, encryption, pseudonymisation, and black-box redaction.<\/span><\/p>\n

This article provides standalone examples of PDF masking and image masking via DarkShield Jobs, created through wizards in the IRI Workbench GUI for DarkShield<\/a>. For a more general discussion of using the GUI for all kinds of files, see this article<\/a>.<\/span><\/p>\n

Challenges with PDFs and Images<\/b><\/h5>\n

Searching and masking can at times present file-type-specific challenges. This is the result of files varying in their format, how data is stored in files, and the necessary techniques used to access and manipulate data in these files. Broadly speaking, PDF and image files can represent an outsized challenge for both search and masking operations.<\/span><\/p>\n

Search Challenges<\/b><\/h5>\n

Technical limitations around PDF and image files can hamper the ability of software to find and extract PII from them. More specifically, both the quality and format of the files can determine whether complications will arise during the search process.\u00a0\u00a0<\/span><\/p>\n

PII in images is translated to text using OCR (optical character recognition). The OCR model IRI ships with DarkShield can be used as is or fine-tuned (trained) to perform at a higher level of accuracy.\u00a0<\/span><\/p>\n

Low-quality images present a significant challenge. Specifically, images with low resolution, images containing multi-colored backgrounds, and text that cannot be easily read (e.g., in a very unique font or handwritten characters) may cause the OCR engine to stumble.<\/span><\/p>\n

Searching for PII in PDFs also has its own set of challenges. You may need to extract the PII either from within form fields (fairly straightforward), or from free-form text based on X,Y coordinate specifications. Unfortunately, there are several challenges with the latter.\u00a0<\/span><\/p>\n

The first problem is that because characters are X,Y coordinate positioned, the use of spaces and tabs is not guaranteed. Moreover, null values can be in different locations to represent that there are \u201cspaces\u201d in a line and\/or line breaks to indicate the end of a line or sentence.\u00a0<\/span><\/p>\n

Either way, this can result in sentences that are broken up incorrectly because of these faulty characters. That can disrupt content interpretation and thus the accuracy of Named Entity Recognition in searches.<\/span><\/p>\n

Another problem with PDF character reading is the possibility of slight differences in Y elevation of characters on the same line. This commonly occurs when there are subscripts and superscripts. This is a serious problem when extracting text that is above an underline.\u00a0\u00a0<\/span><\/p>\n

Consider this PDF from which text must be extracted for identification and\u00a0<\/span>masking to occur:\u00a0\u00a0<\/span><\/p>\n

\"\"<\/p>\n

Below is the PDF processor\u2019s extracted text that has difficulty reading words hovering above lines.<\/span><\/p>\n

\"\"<\/p>\n

Yet another problem is that PDFs can have images embedded within. That loops back to the problems with images.<\/span><\/p>\n

Recommendations<\/b><\/h5>\n

Some of the issues mentioned above can be alleviated by providing images with decent resolution quality and monochrome backgrounds (as much as possible). IRI also recommends modifying your DarkShield File Configurations as needed for a more tailored processing of these file types.<\/span><\/p>\n

File configurations for images that may help include:<\/span><\/p>\n