HSM Integration

★ Pro — Commercial License Required

HSM integration requires the Pro package and a PKCS#11-compatible hardware device.

TCPDF-Next Pro supports signing with Hardware Security Modules (HSMs), smart cards, and USB tokens via PKCS#11. Private keys never leave the hardware device.

HSM Classes

Class	Purpose
HsmSigner	Implements SignerInterface for HSM-based signing
Pkcs11Bridge	Low-level PKCS#11 library communication

Pkcs11Bridge

Manages the connection to a PKCS#11 library.

use Yeeefang\TcpdfNext\Pro\Security\Hsm\Pkcs11Bridge;

$bridge = new Pkcs11Bridge(
    libraryPath: '/usr/lib/softhsm/libsofthsm2.so',
    slotId:      0,
    pin:         $_ENV['PKCS11_PIN'], // never hardcode PINs
);

// List available keys
$keys = $bridge->listPrivateKeys();
foreach ($keys as $key) {
    echo $key->label(); // "signing-key-2026"
    echo $key->type();  // 'RSA', 'EC'
}

HsmSigner

Drop-in replacement for software-based signing in the DigitalSigner workflow.

use Yeeefang\TcpdfNext\Core\Document;
use Yeeefang\TcpdfNext\Pro\Security\Hsm\{HsmSigner, Pkcs11Bridge};
use Yeeefang\TcpdfNext\Pro\Security\Signature\DigitalSigner;
use Yeeefang\TcpdfNext\Pro\Security\Timestamp\TsaClient;
use Yeeefang\TcpdfNext\Contracts\Enums\SignatureLevel;

$pdf = Document::create()->addPage()->text('HSM-signed document.');

$bridge = new Pkcs11Bridge(
    libraryPath: $_ENV['PKCS11_LIBRARY'],
    slotId:      (int) $_ENV['PKCS11_SLOT'],
    pin:         $_ENV['PKCS11_PIN'],
);

$hsm = new HsmSigner($bridge);
$hsm->selectKey(label: 'signing-key-2026');
$hsm->certificate('/certs/hsm-signing.pem');
$hsm->chain(['/certs/intermediate.pem', '/certs/root.pem']);

$signer = new DigitalSigner($hsm);
$signer->level(SignatureLevel::PAdES_B_LTA);
$signer->timestampAuthority(new TsaClient('https://tsa.example.com/timestamp'));
$signer->reason('Enterprise archival signature');

$signer->sign($pdf);
$pdf->save('/output/hsm-signed.pdf');

Supported HSMs

Any PKCS#11-compatible device works. Common examples:

Device	Library Path (typical)
SoftHSM 2 (testing)	/usr/lib/softhsm/libsofthsm2.so
Thales Luna	/usr/lib/libCryptoki2_64.so
AWS CloudHSM	/opt/cloudhsm/lib/libcloudhsm_pkcs11.so
YubiKey (PIV)	/usr/lib/libykcs11.so
SafeNet eToken	C:\Windows\System32\eTPKCS11.dll

Signature Algorithms

$hsm->algorithm('sha256WithRSAEncryption');  // default
$hsm->algorithm('sha256WithRSAPSS');         // RSASSA-PSS
$hsm->algorithm('ecdsaWithSHA256');          // ECDSA P-256

Algorithm	Notes
RSA PKCS#1 v1.5 (SHA-256/384/512)	Most widely compatible
RSASSA-PSS (SHA-256)	Recommended for new deployments
ECDSA (P-256 / P-384)	Smaller, faster signatures

Testing with SoftHSM 2

apt-get install softhsm2
softhsm2-util --init-token --slot 0 --label "test-token" \
  --so-pin 87654321 --pin 12345678
pkcs11-tool --module /usr/lib/softhsm/libsofthsm2.so \
  --login --pin 12345678 \
  --keypairgen --key-type rsa:2048 --label "signing-key-2026" --id 01

Error Handling

use Yeeefang\TcpdfNext\Pro\Security\Hsm\HsmException;

try {
    $bridge->openSession();
} catch (HsmException $e) {
    echo $e->getMessage(); // "PKCS#11 error: CKR_PIN_INCORRECT"
}

PKCS#11 Code	Meaning
CKR_PIN_INCORRECT	Wrong PIN
CKR_PIN_LOCKED	PIN locked after too many attempts
CKR_TOKEN_NOT_PRESENT	HSM device not connected
CKR_KEY_HANDLE_INVALID	Key not found on the token

Next Steps

• PAdES Digital Signatures -- Full signature pipeline from B-B to B-LTA.
• Long-Term Validation -- DSS, OCSP, CRL, and archival timestamps.
• Pro Package Overview -- Full module listing and license information.