PHP ActiveX

Export a Public Key as PEM

Demonstrates the Chilkat PublicKey.GetPem method, which returns the public key in PEM format. The only argument selects the underlying DER representation: true prefers the traditional PKCS #1 form (RSA), false uses the SubjectPublicKeyInfo form.

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: PEM is the most portable way to share a public key — the Base64 text block most tooling reads. The boolean picks the encoding: false produces the modern, algorithm-independent PUBLIC KEY (SubjectPublicKeyInfo), which is the usual choice; true produces the older RSA-specific RSA PUBLIC KEY for tools that require it. A public key is not sensitive, so the PEM can be distributed openly.

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<?php

$success = 0;

//  Load a public key to export.  LoadFromFile inspects the content, so it accepts DER, PEM, XML,
//  JWK, and other supported representations.
$pubKey = new COM("Chilkat.PublicKey");
$success = $pubKey->LoadFromFile('qa_data/public.pem');
if ($success == 0) {
    print $pubKey->LastErrorText . "\n";
    exit;
}

//  Export the public key in PEM format.  The argument selects the underlying DER representation:
//  1 prefers the traditional PKCS #1 form (RSA), 0 uses the SubjectPublicKeyInfo form.
$preferPkcs1 = 0;
$pem = $pubKey->getPem($preferPkcs1);
if ($pubKey->LastMethodSuccess == 0) {
    print $pubKey->LastErrorText . "\n";
    exit;
}

print $pem . "\n";

?>