Represents the "StrF" entry of the encryption dictionary object.

It is an optional entry defined as part of the PDF 1.5 specification.

It contains a string representing a PDF name object.

The PDF specification states that this item assumes a value of "Identity" if no value has been provided.

For definitive details see:.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 20, page 57.

Adobe Supplement to the ISO 32000, BaseVersion: 1.7, ExtensionLevel: 3; Table: 3.18, page 14.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 20, page 72.