Redaction

Redaction and security – Read this first

You can use PixEdit or PixView to redact, or censor, confidential information in a document by “blacking out” selected words or sentences. PixEdit and PixView offer a safe way to do this, even on documents that contains hidden OCR text. Even though PixEdit and PixView does this in a safe way, it is still recommended to read though the following information about security aspects of redaction.

Redaction directly on paper before scanning Avoid using ink for manual redaction directly on the original paper document. The reason is that modern software such as PixEdit® or PhotoShop® in some cases may be used to separate the ink redaction from the text if the document has been scanned in greyshade or full color mode. If the document has already been manually redacted, you may consider using PixEdit or PixView to re-redact after scanning to make sure that the ink cannot be removed digitally. If you do not want to re-redact, consider to scanning your document in pure black/white mode or reduce the color depth after scanning by using the PixEdit menu Image, Colors, Convert to black and white. Ink redactions in pure black and white documents are usually impossible to remove by digital means.

Digitally born documents Note that redaction by putting black color over sensitive words by the use of a word processor and then export the file to PDF is not a safe method. The reason is that some combinations of word processors and PDF export software may include the redacted text itself beneath the black color in the final PDF file. By the use of ordinary software, the black layer may easily be removed so that the redacted text is revealed. If you use PixEdit or PixView to redact digitally born documents however, the redacted text will be permanently removed.

Redacting using non-dedicated software Some general PDF editors may simply add a layer of black above text in scanned documents without removing the text itself. If you use a general PDF editor with unsuitable graphic tools for redacting, you should check if the redacted text as well as any invisible OCR layer is really gone after saving. PixEdit however, always permanently removes graphics as well as hidden OCR-text in scanned documents when you use, for example, filled rectangles. It is handier however, to use the dedicated redaction tool in PixEdit or PixView.

Partly translucent pages Note that when scanning partly translucent documents, some information may leak between opposite pages especially if you scan in grayscale or full color mode. This information leak may be almost invisible to the eye, and sometimes even undetectable. However, such faint information can be enhanced by modern software and be made readable by a technically skilled operator.

Figure: A real-world example of retrieved text from the opposite side of a thin, scanned front page. Only the front page was scanned. The text from the opposite page was enhanced and mirrored by PixEdit.

For the above reason, redacted, double sided, thin pages may create a special security problem. Please consider to scan such documents in black/white mode or to convert the scanned document to black/white using Image, Colors, Convert to black and white before or after redaction. As an alternative, use Image, Colors, Drop color and select white with a tolerance of 5%. This will usually remove any leaked graphics from opposite pages.

 Redacting

The redaction tool provides a safe way of censoring both digitally born and scanned documents. Any hidden OCR text as well as the graphic representation of the redacted text will be permanently removed. It will not be possible to retrieve the redacted text after saving a redacted document.

How to redact Activate the redaction tool and select the area you want to redact. The selected area will be blacked out. If you have PixEdit with the OCR option, PixEdit will offer you to search for other instances of the same word you have just redacted so that they can be redacted automatically. The tool style window must be visible in order to do this. Hit F10 if the tool style window is not visible. This option is not available in PixView. 

Instead of manually selecting the text to be redacted, you may type a word or text in the redaction tool style window and click the search button to display a list of candidates to be redacted. By default, all listed candidates will be selected and redacted when you click the “Redact selected” button.

When redacting documents that are not digitally born, PixEdit uses OCR-technology to search for candidates to be redacted. If the document has poor quality, the automatic search function may not find all candidates. It is therefore good practice to always check if all candidates have been found after automatic redaction.

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