Rust

Sign PDF: Choosing RSASSA-PSS or PKCS1-v1_5 and Hash Algorithm

See more PDF Signatures Examples

This example demonstrates how to choose between RSASSA-PSS vs. PKCS1-v1_5 and the hash algorithm when signing a PDF. Rust

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

let pdf = chilkat::Pdf::new();

// Load a PDF to be signed.
// The "hello.pdf" is available at https://chilkatsoft.com/hello.pdf
if pdf.load_file("qa_data/pdf/hello.pdf").is_err() {
    println!("{}", pdf.last_error_text());
    return;
}

// Options for signing are specified in JSON.
let json = chilkat::JsonObject::new();

// In most cases, the signingCertificateV2 attribute is needed.
let _ = json.update_int("signingCertificateV2", 1);

// ---------------------------------------------------------------------------------------------------------------------------
// This example is the same as the example at Sign a PDF (Simplest Example Possible)
// but with the following lines added to specify the signature scheme and hash algorithm.

// The signature schemes PKCS-v1_5 and RSASSA-PSS have differences. 
// PKCSV1_5 is deterministic. The same message and key will produce an identical signature value each time. 
// PSS is randomized and will produce a different signature value each time.

// To choose the hash algorithm:
// (The typical choices are sha1, sha256, sha384, and sha512.)
let _ = json.update_string("hashAlgorithm", "sha256");

// To choose PKCSV1_5:
let _ = json.update_string("signingAlgorithm", "pkcs");
// Alternatively, to choose RSASSA-PSS:
let _ = json.update_string("signingAlgorithm", "pss");

// If not specified, the default is SHA256 with PKCS-v1_5.

// The remainder of this example is the same as the example at Sign a PDF (Simplest Example Possible)
// ---------------------------------------------------------------------------------------------------------------------------

// Put the signature on page 1, top left
let _ = json.update_int("page", 1);
let _ = json.update_string("appearance.y", "top");
let _ = json.update_string("appearance.x", "left");

// Use a font scale of 10.0
let _ = json.update_string("appearance.fontScale", "10.0");

// In this example, the appearance of the digital signature will contain three lines:
// 1) The signing certificate's common name
// 2) The current date/time
// 3) Some arbitrary text.
// The keyword "cert_cn" is replaced with the Certificate's Subject Common Name.
// The keyword "current_dt" is replaced with the current date/time.
// Any number of appearance text lines can be added.
let _ = json.update_string("appearance.text[0]", "Digitally signed by: cert_cn");
let _ = json.update_string("appearance.text[1]", "current_dt");
let _ = json.update_string("appearance.text[2]", "The crazy brown fox jumps over the lazy dog.");

// Load the signing certificate. (Use your own certificate.)
let cert = chilkat::Cert::new();
if cert.load_pfx_file("qa_data/pfx/myPdfSigningCert.pfx", "secret").is_err() {
    println!("{}", cert.last_error_text());
    return;
}

// Tell the pdf object to use the certificate for signing.
if pdf.set_signing_cert(&cert).is_err() {
    println!("{}", pdf.last_error_text());
    return;
}

if pdf.sign_pdf(&json, "qa_output/hello_signed.pdf").is_err() {
    println!("{}", pdf.last_error_text());
    return;
}

println!("The PDF has been successfully cryptographically signed.");

// The appearance of the signature appears in Adobe Acrobat as shown here:

// (image:https://example-code.com/images/signature1.jpg/endImage)