PHP OpenSSL Error

Question

I am getting the error Warning: openssl_get_publickey() [function.openssl-get-publickey]: Don't know how to get public key from this private key on line 5 When trying to get a public key from a private key. Here is my PHP code:

<?php
$privatekeyorig = openssl_pkey_new();
openssl_pkey_export($privatekeyorig,$privatekey);
echo '<b>Private Key:</b> ' . $privatekey . '<br>';
$publickey = openssl_get_publickey($privatekeyorig);
echo '<b>Public Key:</b> ' . $publickey . '<br>';
?>

According to the PHP manual I am doing this correctly. Anyone spot an error? Help would be greatly appreciated!

neubert · Accepted Answer · 2012-06-06 21:04:18Z

2

My recommendation would be to use phpseclib, a pure PHP RSA implementation. eg.

<?php
include('Crypt/RSA.php');

$rsa = new Crypt_RSA();
$rsa->loadKey('...');

$privatekey = $rsa->getPrivateKey();
$publickey = $rsa->getPublicKey();
?>

answered Jun 6, 2012 at 21:04

neubert

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2 Comments

Ethan H Over a year ago

Unfortunately I can't install anything on my host and since OpenSSL is already installed I thought it might work. I also can't use mcrypt as I need asymmetrical encryption.

neubert Over a year ago

You don't need to install anything. Just upload the PHP files and you're done. That's the whole point of phpseclib. The developer went to great pains to make sure that not even bcmath or gmp were required. They're used if they're available, for speed, but aren't required.

walrii · Accepted Answer · 2012-06-07 00:00:51Z

1

Check out the last comment on http://php.net/manual/en/function.openssl-pkey-new.php

[UPDATE] From the comment right before the above :) and it works on my system to give you a textual public key:

// Create the keypair
$res=openssl_pkey_new();

// Get private key
openssl_pkey_export($res, $privkey);

// Get public key
$pubkey=openssl_pkey_get_details($res);
$pubkey=$pubkey["key"];

edited Jun 7, 2012 at 0:00

answered Jun 6, 2012 at 3:17

walrii

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3 Comments

Ethan H Over a year ago

I already looked at that - it is exporting the key as a certificate I want it to be a plain text key, just like the private key I have generated.

walrii Over a year ago

@ethanh The comment prior to the last one is more useful then. I updated the answer.

walrii Over a year ago

Is there something wrong with this answer? I'm curious why it got down voted.

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