Develop a PDF failproof and hacking-proof "marking" software to be run on Linux machine

This project received 4 bids from talented freelancers with an average bid price of $438 USD.

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$250 - $750 USD
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Project Description

Hello everybody,


I have on my forum a database of files downloadable and uploadable by end users. I need a software application to “mark” every single file we have on our database with a specific and unique encrypted sequence, totally invisible to end user.

This sequence has then to be saved on a database and associated with the file itself. I will later use this information to check, when my users will upload new documents, whether these already are on our database or not.


• The software will run on a Linux machine

• The “mark” has not to affect the user experience in reading the pdf in any way

• I don’t need a DRM application. Files have to be fully open-able with no “expiration” date. I just need to mark each file “invisibly”.

• The software has to operate so that for those who want to hack or circumvent this encryption it is impossible to: 1) delete it with other PDF watermarking/unlocking softwares 2)reverse engineer the algorithm

• The software application has to be built under the “black box” principle: I provide some input, it provides us back with the output. These are the functions that we need 1)Checkfile 2)ProtectFile

1) Input: file_name; file_path

Output: Outcome (Y|N); steg_unique_sequence_found [if any]; duplicate_file_found [if any]; duplicate_file_path [if any];

2) Input: file_name; file_path

Output: Outcome (Y|N); Error [if any]; Outcome_file_path; outcome_file_name; outcome_file_specific sequence; steg_unique_sequence

• Encripted sequence has to be added to every single page

• The software has to be “fail proof” and work on any type of pdf (even protected ones), with pages of any dimension).


• I need the property of the source code of this application.

• I need a ready-to-use software with a proper instruction manual

• I need a developer with previous experience in programming and encryption algorithm

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