隐写在PDF文件中 [英] Steganography in PDF files

问题描述

有人可以告诉我，哪里可以隐藏一些数据到PDF文件？换句话说，PDF文件中的隐写。有没有什么算法可以做到这一点？

解决方案

有很多方法可以做到这一点，包括

• 使用传统的图像隐写工具将信息嵌入到图像中，然后将图像嵌入到PDF中。
  
• 将文本颜色设置为白色并确保您没有使用彩色背景。
  
• 在文本上添加一个白色矩形。


• 使用适当的低级工具创建文本你的秘密文本的对象，然后将这些对象标记为已删除。只要没有人试图压缩你的PDF（Pitstop是一个这样的压缩/清理工具），你的数据就会存在。


• 如果你真的感到乐观，那么开始阅读 PDF规范（我不是当然，如果这是最近的一个，那已经过了几年了）。有/是一个交叉引用表，列出文件中当前正在使用的部分。添加几个洞就足够了。

Can somebody tell me, where is possible to hide some data into PDF file? In other words, steganography in PDF files. Is there any algorithm to do this?

解决方案

There are lots of ways to do this, including

• Embed the info into an image using traditional image steganography tools then embed the image into the PDF
• Set the text color to white and make sure you are not using a colored background
• Superimpose a white rectangle over your text.
• Using the appropriate low level tools, create the text objects of your secret text then mark those objects as deleted. As long as no one tries to compact your PDF (Pitstop is one such compression/cleaning tool), your data will exist.
• If you're really feeling optimistic, start reading the PDF Specification (I'm not sure if this is the most recent one, it's been a few years). There is/was a cross-ref table that would list the parts of the file that were "currently in use". It would be easy enough to add a few holes to that.

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