如何区分两个加密/安全的 PDF 文件 [英] How to distinguish between two encrypted / secured PDF files

问题描述

我有两个安全的 pdf 文件.一个有密码，另一个是安全的，但没有密码.我正在使用 PDF 框.如何识别哪个文件有密码，哪个文件是安全的但没有密码?

I have two secured pdf files. One has a password and the other one is secured but without password. I am using PDF Box. How can I identify which file has password and which one is secured but without password?

推荐答案

PDF 有两种加密方式 -

PDF's have two type of encryption -

• 所有者密码 - PDF 所有者/创建者设置的密码以限制其使用(例如编辑、打印、复制等)
• 用户密码 - 打开/查看 PDF 的密码设置

• Owner password - Password set by PDF owner / creator to restrict its usage (e.g. edit, print, copy etc)
• User password - Password set to open / view the PDF

PDF 可以只有所有者密码或两者都有；但不仅是用户密码.在任何一种情况下，PDF 都被称为加密，并且没有直接的 API 来区分两种加密.

PDF can have only owner password or both; but not only user password. In either case the PDF is termed to be encrypted and there is no direct API to distinguish between two kind of encryption.

对于PDFBox，您可以使用以下代码片段来确定它是否已加密；并区分它是只有所有者密码还是两者都有.

In case of PDFBox you can use below code snippet to determine if it is encrypted or not; and distinguish whether it has only owner password or both.

PDDocument pdfDoc = PDDocument.load(new File("path/to/pdf"));
boolean hasOwnerPwd = false;
boolean hasUserPwd = false;
if(pdfDoc.isEncrypted()){
    hasOwnerPwd = true;
    try{
        StandardDecryptionMaterial sdm = new StandardDecryptionMaterial(null);
        pdfDoc.openProtection(sdm);
        hasUserPwd = true;
    } catch(Exception e){
        // handle exception
    }
}

参见 PDFBox API 文档 这里 和 这里.

See PDFBox API docs here and here.

编辑 感谢蒂尔曼指出最新的代码和替代方法来确定/区分两种加密.更新了代码片段并相应地发布.

EDIT Thanks to Tilman to point out latest code and alternate way to determine / distinguish between two encryption. Updated the code snippet and post accordingly.

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