.NET Core C# Requires Chilkat v11.7.0+

Choose the PDF Encryption Algorithm: AES-256, AES-128 or RC4

See more PDF Protection Examples

Demonstrates the algorithmChoice option of the encrypt operation. aes-256 is the default and the one to use unless an older reader must open the file. aes-128 is for readers that predate AES-256. rc4-128 and rc4-40 are broken ciphers kept only for very old readers. Each algorithm needs a minimum PDF version, and the file header is raised to it when the PDF is saved, never lowered. A PDF saved with RC4 is written with a classic cross-reference table so that those old readers can parse it. .NET Core C#

bool success = false;

//  This example requires the Chilkat API to have been previously unlocked.
//  See Global Unlock Sample for sample code.

//  The PDF used in this example is available at two_page_memo.pdf

Chilkat.JsonObject json = new Chilkat.JsonObject();
Chilkat.JsonObject jsonOut = new Chilkat.JsonObject();
Chilkat.JsonObject info = new Chilkat.JsonObject();

//  AES-256, the default.  Saved as PDF 1.7 with Adobe extension level 8.
Chilkat.Pdf pdf1 = new Chilkat.Pdf();
success = pdf1.LoadFile("qa_data/pdf/two_page_memo.pdf");
if (success == false) {
    Debug.WriteLine(pdf1.LastErrorText);
    return;
}

pdf1.UserPassword = "user-secret";
pdf1.OwnerPassword = "owner-secret";
json.UpdateString("algorithmChoice","aes-256");
success = pdf1.Protection("encrypt",json,jsonOut);
if (success == false) {
    Debug.WriteLine(pdf1.LastErrorText);
    return;
}

Debug.WriteLine("aes-256 will be saved as PDF " + jsonOut.StringOf("pending.pdfVersion") + ", Adobe extension level " + Convert.ToString(jsonOut.IntOf("pending.adobeExtensionLevel")));
success = pdf1.WriteFile("qa_output/memo_aes256.pdf");
if (success == false) {
    Debug.WriteLine(pdf1.LastErrorText);
    return;
}

success = pdf1.PreLoadCheck("qa_output/memo_aes256.pdf",info);
if (success == false) {
    Debug.WriteLine(pdf1.LastErrorText);
    return;
}

Debug.WriteLine("  saved file: " + info.StringOf("algorithm") + ", PDF " + info.StringOf("pdfVersion"));

//  AES-128, for readers that predate AES-256.  Saved as PDF 1.6.
Chilkat.Pdf pdf2 = new Chilkat.Pdf();
success = pdf2.LoadFile("qa_data/pdf/two_page_memo.pdf");
if (success == false) {
    Debug.WriteLine(pdf2.LastErrorText);
    return;
}

pdf2.UserPassword = "user-secret";
pdf2.OwnerPassword = "owner-secret";
json.UpdateString("algorithmChoice","aes-128");
success = pdf2.Protection("encrypt",json,jsonOut);
if (success == false) {
    Debug.WriteLine(pdf2.LastErrorText);
    return;
}

Debug.WriteLine("aes-128 will be saved as PDF " + jsonOut.StringOf("pending.pdfVersion"));
success = pdf2.WriteFile("qa_output/memo_aes128.pdf");
if (success == false) {
    Debug.WriteLine(pdf2.LastErrorText);
    return;
}

success = pdf2.PreLoadCheck("qa_output/memo_aes128.pdf",info);
if (success == false) {
    Debug.WriteLine(pdf2.LastErrorText);
    return;
}

Debug.WriteLine("  saved file: " + info.StringOf("algorithm") + ", PDF " + info.StringOf("pdfVersion"));

//  RC4-128, a broken cipher, only for readers too old for AES.  Saved as PDF 1.4.
Chilkat.Pdf pdf3 = new Chilkat.Pdf();
success = pdf3.LoadFile("qa_data/pdf/two_page_memo.pdf");
if (success == false) {
    Debug.WriteLine(pdf3.LastErrorText);
    return;
}

pdf3.UserPassword = "user-secret";
pdf3.OwnerPassword = "owner-secret";
json.UpdateString("algorithmChoice","rc4-128");
success = pdf3.Protection("encrypt",json,jsonOut);
if (success == false) {
    Debug.WriteLine(pdf3.LastErrorText);
    return;
}

Debug.WriteLine("rc4-128 will be saved as PDF " + jsonOut.StringOf("pending.pdfVersion"));
success = pdf3.WriteFile("qa_output/memo_rc4_128.pdf");
if (success == false) {
    Debug.WriteLine(pdf3.LastErrorText);
    return;
}

success = pdf3.PreLoadCheck("qa_output/memo_rc4_128.pdf",info);
if (success == false) {
    Debug.WriteLine(pdf3.LastErrorText);
    return;
}

Debug.WriteLine("  saved file: " + info.StringOf("algorithm") + ", PDF " + info.StringOf("pdfVersion"));

//  Sample output:

//  aes-256 will be saved as PDF 1.7, Adobe extension level 8
//    saved file: aes-256, PDF 1.7
//  aes-128 will be saved as PDF 1.6
//    saved file: aes-128, PDF 1.6
//  rc4-128 will be saved as PDF 1.4
//    saved file: rc4-128, PDF 1.4