(PHP Extension) RSASSA-PSS Sign String to Create Base64 PCKS7 Signature

Signs a string to create a PKCS7 signature in the base64 encoding. The signature algorithm is RSASSA-PSS with SHA256.

Note: This example requires Chilkat v9.5.0.67 or greater.

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<?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 requires the Chilkat Crypt API to have been previously unlocked.
// See Unlock Chilkat Crypt for sample code.

$crypt = new CkCrypt2();

// Get a digital certificate with private key from a .pfx
// (Chilkat has many different ways to provide a cert + private key for siging.
// Using a PFX is just one possible option.)
$pfx = new CkPfx();
$success = $pfx->LoadPfxFile('qa_data/rsassa-pss/privatekey.pfx','PFX_PASSWORD');
if ($success != true) {
    print $pfx->lastErrorText() . "\n";
    exit;
}

// Get the certificate to be used for signing.
// (The typical case for a PFX is that it contains a cert with an associated private key,
// as well as other certificates in the chain of authentication.  The cert with the private
// key should be in the first position at index 0.)
// cert is a CkCert
$cert = $pfx->GetCert(0);
if ($pfx->get_LastMethodSuccess() != true) {
    print $pfx->lastErrorText() . "\n";
    exit;
}

$crypt->SetSigningCert($cert);

// Indicate that RSASSA-PSS with SHA256 should be used.
$crypt->put_SigningAlg('pss');
$crypt->put_HashAlgorithm('sha256');

$crypt->put_EncodingMode('base64');

// Sign a string and return the base64 PKCS7 detached signature
$originalText = 'This is a test';
$pkcs7sig = $crypt->signStringENC($originalText);
print 'Detached Signature:' . "\n";
print $pkcs7sig . "\n";

// This signature looks like this:
// MIIG5wYJKoZIhvcNAQcCoIIG2DCCBtQCAQExDzANBgl .. YToLqEwTdU87ox5g7rvw==

// The ASN.1 of the signature can be examined by browsing to https://lapo.it/asn1js/ ,
// then copy-and-paste the Base64 signature into the form and decode..

// The signature can be verified against the original data like this:
$success = $crypt->VerifyStringENC($originalText,$pkcs7sig);
print 'Signature verified: ' . $success . "\n";
$success = $crypt->VerifyStringENC('Not the original text',$pkcs7sig);
print 'Signature verified: ' . $success . "\n";

// Now we'll create an opaque signature (the opposite of a detached signature). 
// An opaque signature is a PKCS7 message that contains both the original data and
// the signature.  The verification process extracts the original data.
$opaqueSig = $crypt->opaqueSignStringENC($originalText);
print 'Opaque Signature:' . "\n";
print $opaqueSig . "\n";

// The ASN.1 of the signature can be examined by browsing to https://lapo.it/asn1js/ ,
// then copy-and-paste the Base64 signature into the form and decode..

// We can verify and extract the original data:
$origTxt = $crypt->opaqueVerifyStringENC($opaqueSig);
if ($crypt->get_LastMethodSuccess() != true) {
    print 'Signature verification failed.' . "\n";
    print $crypt->lastErrorText() . "\n";

    exit;
}

print 'Signature verified.' . "\n";
print 'Extracted text:' . $origTxt . "\n";


?>