I have a problem about PDF file encryption using php.
Case: Let's say I have a local system (web based) to upload and download files, such as 4sh*red (dot) com, but it just allows PDF file. A user sign up and login to download the PDF files using his or her own personal computer. After users downloaded a PDF file from my system, the file can be viewed only on computer where they downloaded the file. But, if another user copy it (I mean: downloaded PDF file) to another computer, the file can't be viewed on that computer.
Note: I don't mean here about protecting the PDF files using password because nowadays there are a lot of softwares used to remove PDF's password protection. But, the file can't be viewed at all if copied to another computer.
Can we do that in php? If yes, do you know any algorithm to solve the case?
I really appreciate your response or answers.
Thank you.
The PDF format is an open format by Adobe. This means there are a lot of programs out there that can read it and quite same that can modify it.
If you write your own program and add some stuff to the PDF, then maybe you can do this.
Another question is - why don't you just make the document visible in the web browser to the user? Of course there's still going to be a way around for savvy users to get it, but most noobs wouldn't know how and you can easily close the simplest blocks (like right click / save).
What maybe interesting to do is what a lot of companies are doing with videos nowadays: you can dynamically add some hidden or visible 'info' to a PDF that identifies who you sent it to. In that way, if the PDF shows up somewhere else - you know who spread it.... Again - PDF is an open format, so anyone can always erase whatever you write in the main contents, so you'd have to add a hidden image to the content or something.
Related
I have a Notes app that was designed for the browser, not the client. It allowed upload of files into the documents, so nearly all the documents have files. The files are stored in the NSF as $FILE and displayed in the documents as links.
I am using Adobe Acrobat Pro to create PDFs from the documents and need to include the file attachments within the PDFs, however the PDFs just include links to the files, not the attachments. Can I write an agent to run against the documents to get those files and embed them within the documents? When I view those documents through the client, I see all of the HTML etc. and then at the bottom of the document, the file attachments appear. When I view these same documents in the browser, the file attachments do not appear. If I could merely ensure that they are there, then when running the PDF generator in Acrobat Pro, they would be included in the PDFs and executable.
I am really stuck here, with no other way to 'archive' this notes database with all the data intact.
Thanks in advance for any insights!!
Ginni
There is a commercial product from Swing Software that does this. I hear that it's quite good, but I've never used it. Let me explain why...
The way I usually end up doing this is just quick-and-dirty. I write an agent to export the files, using the document UNID as part of the filename. The same agent exports all the data fields from the document into a CSV file, and I add a column with the filename of the extracted attachment. In your case, I would add two columns -- one for the extracted attachment(s), and one for the generated PDF. The CSV serves as an index for the exported data. It can be imported into something more friendly, or just left as-is and brought up in Excel, depending on the customer's usage requirements and available systems. I've recommended Swing Software's product and offered to explore other ideas for developing code (e.g., using wkhtmltopdf for Domino web apps to capture a WYSIWYG rendering based on an HTML crawl) for PDF rendering of Notes documents for a couple of clients, but none of them have justified the cost that would be involved in buying licenses and/or writing the code. Quick and dirty always seems to win, even when there are retention and eDiscovery considerations taken into account.
in our online laboratory software (php) we want to upload some files and allow users to print these documents. Bu we have to block downloading them, because user can print from downloaded file, if we upload newer version of document this will be a problem.
Is there any way to block downlodin these documents?
I am not sure if what you ask for is possible, because I can always print a file as pdf to my desktop instead to my printer if I wanted. My organisation handles this issue by having a watermark on all PDF files that says "Uncontrolled copy when printed", so even if someone prints it out they will know that it might be outdated and should be careful.
I am working on vb.net application where I wanted to create and read a file. File will have specific extension for ex. .abcb the way I want my application to work is:
can create a file with .abcd extension
should read .abcd files only(and also application created files only so altered extension shouldn't be working)
.abcd files should show some garbage data when open in any other application(ex. word, notepad any image viewer etc.)
Now my application does 1,2(partly) step, i.e. it creates a file and load data also, it reads .abcd files only(not the altered files)
but created file can be read by other software's also.I tried searching a lot but have not found anything and don't know where to start.
Any help is appreciated!
if you don't want other programs to be able to read the content of your file then your going to have to mask it in some way, which is usually done with encryption.
assuming your not too worried about the key being compromised, the easiest way to accomplish this would be to generate a key with something like System.Security.Cryptography and use that key to encyrpt everything you send to the file and everything you read from it.
as for making your own file extension, you can make the extension of a file whatever you want when you make it:
Dim fs As FileStream = File.Create("/path/to/file/filename" & ".abcd")
the only thing that the extension does is tell the OS what progam to use when opening a file by default, which will probably be notepad since your making your own extension
Problem: Need to convert local html (with local images etc) to pdf from an AIX box running Universe 11.2.5 with System Builder
Current solution: FTP over html file to a Windows server which converts in batches and sends the e-mail to the destination
Proposed Solution: Do everything on the AIX box, from converting html to pdf and sending the e-mail.
Current problem: Unable to find a way to convert local html to PDF on the AIX box. I have been trying many different ways from trying to install Python3, but to no avail.
The only really difficult part of the process is getting the HTML to render into a format will properly display your html into pages that are suitable for printing. There is a fair amount of magic that goes on between HTTP:GET and clicking print on a browser window that needs to be accounted for.
I was trying accomplish something similar many moons ago on AIX but kind of ran into a skill level/time wall because I was going to have essentially create a headless browser to render the html. It looks like there are now some utilities that you might be able to leverage. I found this recent updated article on Super User that actually got me somewhat excited, especially since I don't use AIX anymore so precompiled binaries and well understood and easily attainable dependencies are something I can actually have in my life.
https://superuser.com/questions/280552/how-can-i-render-a-website-as-an-image-from-the-shell
Good Luck.
There seems to be several questions rolled into this one item.
Converting HTML to PDF, while that is just a data manipulation that you could do in basic, writing such code would be a large task. The option you use sending it to another system is valid, but put more points of failure into the system. I would think you could find code to do it on the AIX box.
Rocket plans on getting the MV Python to work on AIX, this will make the converting of html to PDF much easier since there are a lot of open source modules.
As for my suggestion of using sockets, that would be if you intend to send it to a service that will take the htms, and return the pdf document.
i.e. Is there a web service for converting HTML to PDF?
Once you have the pdf document, you can either store it in a UniVerse type-19 file, or do the base64 encoding and store it in UniVerse hash file.
Hope this helps,
Mike
I have a text file. Now I have changed its file type from .txt to .abc. My VB.NET program loads the text into textboxes from that file. After changing the file type, however, other apps like NotePad and Word are able to open and read my .abc file.
Is there any way that only my application will be able to open/read from the file and no other app would be able to do so? What I mean is, suppose I have a PhotoShop document .psd file, no other app, rather that photoshop itself, can open it. How do I make my file unreadable by other apps?
There is no way to prevent an app that you don't develop from opening any file. The extensions are just there for helping us humans, and maybe a bit for the computer to know the default app you select for an extension.
Like you said, a .txt file can be opened by many many apps. You can open a .txt file with Notepad, Firefox, VSCode, and many others.
Same way, a .psd file can be opened by many many apps. You can open that .psd file with Photoshop, but also Notepad, Firefox, and VSCode, and probably the same apps as above.
The difference is which apps can read and understand the file.
In order to make a file not understandable by other apps, you need to make it into a format that cannot recognize, because you planned it "in secret".
Like Visual Vincent said above, you could encrypt the file in a way, or you can have a binary file, that basically only your app knows know to understand.
Since you dont own the app you want the file to be understood by, then you either have to accept that it can be opened by any app that can open files, or you can try to encrypt the file outside the app, or like zipping it with a password, and then decrypting or unzipping when you want to use it.
Firstly, any file can be read unless it is still open by a particular process or service. Even PhotoShop files can be 'read' by NotePad - try it!
So, an attempt at my first answer...
You can try a couple of methods to prevent opening the file, for instance, applying a file lock. As an example, SQL Server .mdf files are locked by the SQL Server service. This happens because the files are maintained in an open state, however; your application would have to remain running to keep these files open. Technically, though, the files can still be copied.
Another way is to set the hidden attribute for the file. This hides the file from the less savvy users, but it will be displayed if the user show's hidden files.
And my second answer: You refer to the format of files by saying only PhotoShop can read or write its own files (not true, but I know what you're saying).
The format of the file must be decided by yourself. You must determine how you are going to store the data that you output from your application. It looks like you have been attempting to write your application data into a text file. Perhaps you should try writing to binary files instead. Binary files, while not encrypted, as suggested by Visual Vincent in the comments to your question, still provide a more tailored approach to storing your data.
Binary files write raw binary data instead of humanised text. For instance, if you write an integer to the file it will appear as a string of four bytes, not your usual 123456789 textual format.
So, you really need to clarify what data you want to write to the file, decide on a set structure to your file (as you also have to be able to read it back in to your application) and then be able to write the information.