Zig Requires Chilkat v11.7.0+

Encrypt a PDF for a Certificate Instead of a Password

See more PDF Protection Examples

Demonstrates certificate security, where a PDF is encrypted for one or more recipients and each opens it with their own certificate and private key. No password is involved. Only the public certificate of a recipient is needed to encrypt. Each recipient has its own permissions, and the changeSecurity permission gives a recipient owner rights. PreLoadCheck tells an application that a file is certificate-encrypted and which certificates can open it. A PDF that cannot be opened, because no matching certificate and private key were provided, fails to load. Zig

const std = @import("std");
const chilkat = @import("chilkat");

pub fn main(init: std.process.Init) !void {
    const alloc = init.arena.allocator();

    // 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

    // The recipient's certificate.  Only the public certificate is needed to encrypt.
    const recipient = try chilkat.Cert.init();
    defer recipient.deinit();
    recipient.loadFromFile("qa_data/certs/recipient.cer") catch {
        std.debug.print("{s}\n", .{try recipient.getLastErrorText(alloc)});
        return;
    };

    const pdf = try chilkat.Pdf.init();
    defer pdf.deinit();
    pdf.loadFile("qa_data/pdf/two_page_memo.pdf") catch {
        std.debug.print("{s}\n", .{try pdf.getLastErrorText(alloc)});
        return;
    };

    // Call AddEncryptCert once for each recipient.
    pdf.addEncryptCert(recipient) catch {
        std.debug.print("{s}\n", .{try pdf.getLastErrorText(alloc)});
        return;
    };

    // recipientPermissions[0] belongs to the first certificate added.  changeSecurity gives that
    // recipient owner rights, so the file can be managed later.
    const json = try chilkat.JsonObject.init();
    defer json.deinit();
    json.updateString("method", "certificate") catch {};
    json.updateBool("recipientPermissions[0].changeSecurity", true) catch {};

    const json_out = try chilkat.JsonObject.init();
    defer json_out.deinit();
    pdf.protection("encrypt", json, json_out) catch {
        std.debug.print("{s}\n", .{try pdf.getLastErrorText(alloc)});
        return;
    };

    std.debug.print("method: {s}\n", .{try json_out.stringOf(alloc, "pending.method")});
    std.debug.print("algorithm: {s}\n", .{try json_out.stringOf(alloc, "pending.algorithm")});
    std.debug.print("recipients: {d}\n", .{json_out.sizeOfArray("pending.recipients")});

    pdf.writeFile("qa_output/memo_for_recipient.pdf") catch {
        std.debug.print("{s}\n", .{try pdf.getLastErrorText(alloc)});
        return;
    };

    // PreLoadCheck says how the file is protected, without loading it.
    const reader = try chilkat.Pdf.init();
    defer reader.deinit();
    const info = try chilkat.JsonObject.init();
    defer info.deinit();
    reader.preLoadCheck("qa_output/memo_for_recipient.pdf", info) catch {
        std.debug.print("{s}\n", .{try reader.getLastErrorText(alloc)});
        return;
    };

    std.debug.print("saved file, method: {s}\n", .{try info.stringOf(alloc, "method")});
    std.debug.print("saved file, recipients: {d}\n", .{info.sizeOfArray("recipients")});

    // The recipient opens it with the certificate and its private key, here from a .pfx file.
    // (On Windows, a certificate that is installed in the Windows certificate store with its private
    // key is found automatically when the PDF is loaded, and SetDecryptCert is not needed for it.)
    const my_cert = try chilkat.Cert.init();
    defer my_cert.deinit();
    my_cert.loadPfxFile("qa_data/pfx/recipient.pfx", "pfx-password") catch {
        std.debug.print("{s}\n", .{try my_cert.getLastErrorText(alloc)});
        return;
    };

    reader.setDecryptCert(my_cert) catch {
        std.debug.print("{s}\n", .{try reader.getLastErrorText(alloc)});
        return;
    };

    reader.loadFile("qa_output/memo_for_recipient.pdf") catch {
        std.debug.print("{s}\n", .{try reader.getLastErrorText(alloc)});
        return;
    };

    const empty = try chilkat.JsonObject.init();
    defer empty.deinit();
    const loaded_info = try chilkat.JsonObject.init();
    defer loaded_info.deinit();
    reader.protection("getInfo", empty, loaded_info) catch {
        std.debug.print("{s}\n", .{try reader.getLastErrorText(alloc)});
        return;
    };

    std.debug.print("opened with: {s}\n", .{try loaded_info.stringOf(alloc, "loaded.openedWith")});
    std.debug.print("pages: {d}\n", .{reader.getNumPages()});

    // Sample output:

    // method: certificate
    // algorithm: aes-256
    // recipients: 1
    // saved file, method: certificate
    // saved file, recipients: 1
    // opened with: certificate
    // pages: 2
}