Perl

A3/A4 Certificate to Create and Verify an Opaque PKCS7/CMS Signature

See more Digital Signatures Examples

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.

Chilkat2 Perl

use strict;
use warnings;
use Chilkat2;

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

my $crypt = Chilkat2::Crypt2->new;

# 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.

my $cert = Chilkat2::Cert->new;

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

my $success = $cert->LoadFromSmartcard('');
if (!$success) {
    print $cert->LastErrorText, "\n";
    exit;
}

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

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

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

# Create the opaque signature:
my $originalData = 'This is the string to be signed.';
my $opaqueSig = $crypt->OpaqueSignStringENC($originalData);
if (!$crypt->LastMethodSuccess) {
    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...

my $vCrypt = Chilkat2::Crypt2->new;

# 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) {
    print $vCrypt->LastErrorText, "\n";
    exit;
}

$vCrypt->EncodingMode('base64');
$vCrypt->Charset('utf-8');

my $extractedData = $vCrypt->OpaqueVerifyStringENC($opaqueSig);
if (!$vCrypt->LastMethodSuccess) {
    print $vCrypt->LastErrorText, "\n";
    exit;
}

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

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