(PHP Extension) A3/A4 Certificate to Create and Verify an Opaque PKCS7/CMS Signature

Demonstrates how to use an A3 or A4 certificate w/ private key on a smartcard or token to create a PKCS7 opaque signature, and also how to verify an opaque signature.

An opaque signature is different than a detached PKCS7 signature in that it contains the original data. Verifying an opaque signature retrieves the original content.

Chilkat PHP Downloads PHP Extension for Windows, Linux, MacOS, Alpine Linux, Solaris

<?php

// The version number (9_5_0) should match version of the Chilkat extension used, omitting the micro-version number.
// For example, if using Chilkat v9.5.0.48, then include as shown here:
include("chilkat_9_5_0.php");

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

$crypt = new CkCrypt2();

// A certificate and private key is needed to create a signature.
// Chilkat provides many different ways to load a certificate and private key, such
// as from a smartcards and hardware tokens, PFX/.p12, Java keystore, JWK, Windows registry-based certificate stores, and other sources.
// This example will load the default certificate from the smartcard that is currently in
// the smartcard reader.

$cert = new CkCert();

// If the smartcard or token requires a PIN, we can set it here to avoid the dialog...
$cert->put_SmartCardPin('000000');

$success = $cert->LoadFromSmartcard('');
if ($success != true) {
    print $cert->lastErrorText() . "\n";
    exit;
}

// Tell it to use the cert and private key we've loaded.
$success = $crypt->SetSigningCert($cert);
if ($success != true) {
    print $crypt->lastErrorText() . "\n";
    exit;
}

// Indicate we want the opaque signature in base64 format:
$crypt->put_EncodingMode('base64');

// Sign the string using the "utf-8" byte representation:
$crypt->put_Charset('utf-8');

// Create the opaque signature:
$originalData = 'This is the string to be signed.';
$opaqueSig = $crypt->opaqueSignStringENC($originalData);
if ($crypt->get_LastMethodSuccess() != true) {
    print $crypt->lastErrorText() . "\n";
    exit;
}

print $opaqueSig . "\n";

// The output looks like this:
// MIIPgQYJKoZIhvcNAQcCoIIPcjCCD24CAQExCzAJBgUrDgMCGgUAMC8GCSqGSIb3DQEHAaAiBCBUaGlzIGlzIHRoZSBzdHJpbmcgdG8gYmUgc...

// ----------------------------------------------------------------------------------------------
// Now let's verify the signature and retrieve the original data.
// We'll use a new Crypt2 object to keep things completely separate...

$vCrypt = new CkCrypt2();

// We only need the certificate to verify a signature (and extract the data from
// an opaque signature).  The public key is always embedded within a certificate.
$success = $vCrypt->SetVerifyCert($cert);
if ($success != true) {
    print $vCrypt->lastErrorText() . "\n";
    exit;
}

$vCrypt->put_EncodingMode('base64');
$vCrypt->put_Charset('utf-8');

$extractedData = $vCrypt->opaqueVerifyStringENC($opaqueSig);
if ($vCrypt->get_LastMethodSuccess() != true) {
    print $vCrypt->lastErrorText() . "\n";
    exit;
}

print 'The extracted data: ' . $extractedData . "\n";

// The output is:
// The extracted data: This is the string to be signed.

?>