Method for inserting and extracting hidden information based on English PDF document

Abstract

The invention relates to a method for inserting and extracting hidden information based on an English PDF document. The inserting method comprises the steps that data streams of the PDF document are read in; hidden information to be inserted is read in and is converted into binary strings; the logic structure of the PDF document is analyzed, and objects of all page content streams are found out; the content streams of the objects of the page content streams are decompressed, an information header of certain bits is inserted in the page content streams to represent the length of the hidden information by modifying the expression mode of display character codes, and the hidden information converted into the binary strings is then inserted after the information header; the content streams are re-compressed and written in a document body; a cross-reference table and a document end are updated according to the change of the length of re-compressed content streams; the PDF document provided with the hidden information in an inserted mode is output. According to the method, the hidden information can be inserted in and extracted from the English PDF document, good visual imperceptibility is achieved, and common editing behaviors to the document are robust.

Description

technical field [0001] The invention relates to the field of multimedia signal processing, more specifically, to a method for embedding and extracting hidden information based on English PDF documents. Background technique [0002] In recent years, with the rapid development of network technology, people have begun to transmit and obtain information more and more through the Internet. At the same time, new office models such as e-commerce and e-government are being widely used, and more and more administrative and commercial documents, such as authorization letters, registration forms, contracts, invoices, etc., have begun to be circulated and transmitted in the form of electronic documents. However, in the open environment of the Internet, malicious acts such as copying and tampering always threaten the copyright ownership of electronic documents, and a large number of copyright theft, illegal transmission, information forgery and other problems emerge in endlessly. Based ...

AI Technical Summary

Problems solved by technology

[0004] Existing information hiding technologies based on PDF documents are easily destroyed by various daily reading operations and saving operations of documents, and the embedded hidden information is difficult to be completely extracted

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