iTextSharp读取PDF与AES加密抛出异常

Question

我试图用AES 256加密的itextsharp打开PDF并显示它。PDF文件也是用itextsharp加密的。我使用的是iTextSharp 5.5.0.0。如果加密设置为"标准加密"，则此代码有效。

内部'using'的右括号抛出异常:算术运算导致溢出。

string path = Server.MapPath("~/App_Data/pdf/foo.pdf");
string password = "openSesame";
Response.Clear();
Response.ClearHeaders();
Response.AddHeader("Expires", "0");
Response.AddHeader("Cache-Control", "private");
Response.AddHeader("content-disposition", "inline");
Response.ContentType = "application/pdf";
using (MemoryStream memoryStream = new MemoryStream())
{
    using (PdfReader reader = new PdfReader(path, Encoding.UTF8.GetBytes(password)))
    using (PdfStamper stamper = new PdfStamper(reader, memoryStream))
    {
    }
    Response.BinaryWrite(memoryStream.GetBuffer());
}
Response.End();

更新(忘记加密代码):

using (FileStream fileStream = new FileStream(path, FileMode.Create))
{
    PdfCopyFields copy = new PdfCopyFields(fileStream);
    var bytes = Encoding.UTF8.GetBytes(password);
    copy.SetEncryption(bytes, bytes, 0, PdfWriter.ENCRYPTION_AES_256);
    // add some documents with 'copy.AddDocument()';
    copy.Close();
}

我错过了什么吗?

Answer 1

下面是我整理的一个快速示例，它可以使用256位AES加密加密PDF:

var openDialog = new OpenFileDialog();
openDialog.DefaultExt = "pdf";
if (openDialog.ShowDialog() == true)
{
    using (var input = openDialog.OpenFile())
    {
        var saveDialog = new SaveFileDialog();
        saveDialog.DefaultExt = "pdf";
        if (saveDialog.ShowDialog() == true)
        {
            using (var reader = new PdfReader(input)) 
            {
                using (var output = saveDialog.OpenFile())
                {
                    PdfEncryptor.Encrypt(
                        reader, output,
                        PdfWriter.ENCRYPTION_AES_256,
                        "password", "password",
                        PdfWriter.ALLOW_PRINTING);
                }
            }
        }
    }
}