PHP ActiveX

Save a Private Key as an Encrypted PKCS #8 DER File

Demonstrates the Chilkat PrivateKey.SavePkcs8EncryptedFile method, which saves the key as password-protected PKCS #8 DER. The first argument is the password and the second is the destination path. The cipher is selected by Pkcs8EncryptAlg.

Note: The file paths are relative to the application's current working directory. Absolute paths may also be used. Supply the paths appropriate to your own environment.

Background: This is the recommended way to persist a key to disk: the binary .der is encrypted under a passphrase, so a stolen file is useless without it. Reach for it whenever a key is stored or shipped. Choose the encryption cipher with Pkcs8EncryptAlg and source the password securely.

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<?php

$success = 0;

//  Load a private key to export.
$privKey = new COM("Chilkat.PrivateKey");
$success = $privKey->LoadPemFile('qa_data/private.pem');
if ($success == 0) {
    print $privKey->LastErrorText . "\n";
    exit;
}

//  The key password is not hard-coded in a real application; obtain it from an interactive
//  prompt, environment variable, or a secrets vault.
$password = 'myKeyPassword';

//  Save as password-protected PKCS #8 DER.  The 1st argument is the password and the 2nd is the
//  destination path.  The cipher is selected by the Pkcs8EncryptAlg property.
$success = $privKey->SavePkcs8EncryptedFile($password,'qa_output/private_pkcs8_enc.der');
if ($success == 0) {
    print $privKey->LastErrorText . "\n";
    exit;
}

print 'Saved (encrypted).' . "\n";

?>