Yonggang Liu

Competitive Advantages: Low performance overhead, Performance overhead constant regardless of document length, Near-perfect accuracy. ??The embodiments present a new class of content masking defenses against the Portable Document Format (PDF) stan­dard. The defenses can identify attacks that cause documents to appear different than the underlying content extracted from the documents. A content masking defense method can include identifying a content masking attack by scanning a document file to extract a character code of a character appearing in the file. Next, the character is rendered based on a font that is embedded in the document file. Optical character recognition can be performed on the rendering, and a content masking attack can be identified based on a comparison of a result of the optical character recognition against the character code of the character.Online information tools compare documents using the underlying text. When documents are attacked the glyphs that display the underlying text change, thus when an OCR reads the document it doesn’t notice the similar text that’s displayed because the underlying text is different. Font verification technique ensures the content integrity of PDF files and protects against content masking attacks. This novel font verification validates the integrity of the embedded fonts andthe integrity of the file content with low performance overhead that is constant irrespective of the document length and with near-perfect accuracy. This has great potential to be used to validate any online documents.