RSA Signature/Verify with .key and .cer

Demonstrates how to use a .key file (private key) and digital certificate (.cer, public key) to create and verify an RSA signature.

Download Chilkat RSA ActiveX

<?php

$privKey = new COM("Chilkat.PrivateKey");

//  Load the private key from an RSA .key file:
$success = $privKey->LoadPemFile('privateKey.key');
if ($success != true) {
    print $privKey->lastErrorText() . "\n";
    exit;
}

//  Get the private key in XML format:
$privKeyXml = $privKey->getXml();

$rsa = new COM("Chilkat.Rsa");

//  Any string argument automatically begins the 30-day trial.
$success = $rsa->UnlockComponent('30-day trial');
if ($success != true) {
    print $rsa->lastErrorText() . "\n";
    exit;
}

//  Import the private key into the RSA component:
$success = $rsa->ImportPrivateKey($privKeyXml);
if ($success != true) {
    print $rsa->lastErrorText() . "\n";
    exit;
}

//  Create the signature as a hex string:
$rsa->EncodingMode = 'hex';

$strData = 'This is the string to be signed.';

//  Sign the string using the sha-1 hash algorithm.
//  Other valid choices are "md2" and "md5".
$hexSig = $rsa->signStringENC($strData,'sha-1');

print $hexSig . "\n";

//  Load a digital certificate from a .cer file:
$cert = new COM("Chilkat.Cert");

$success = $cert->LoadFromFile('myCert.cer');
if ($success != true) {
    print $cert->lastErrorText() . "\n";
    exit;
}

// pubKey is a Chilkat.PublicKey
$pubKey = $cert->ExportPublicKey();

//  Now verify using a separate instance of the RSA object:
$rsa2 = new COM("Chilkat.Rsa");

//  Import the public key into the RSA object:
$success = $rsa2->ImportPublicKey($pubKey->getXml());
if ($success != true) {
    print $rsa2->lastErrorText() . "\n";
    exit;
}

//  The signature is a hex string, so make sure the EncodingMode is correct:
$rsa2->EncodingMode = 'hex';

//  Verify the signature:
$success = $rsa2->VerifyStringENC($strData,'sha-1',$hexSig);
if ($success != true) {
    print $rsa2->lastErrorText() . "\n";
    exit;
}

print 'Success.' . "\n";


?>