PHP openssl encrypt decrypt errors? Not valid public/private keys?

Question

I have this test code in php:

function genPGP() {
    // Create the keypair
    $res=openssl_pkey_new();
    // Get private key
    openssl_pkey_export($res, $prK, bin2hex(mcrypt_create_iv(100, MCRYPT_DEV_URANDOM)));
    // Get public key
    $puK = openssl_pkey_get_public($prK);
    return array($prK,$puK);
}

function prKeyDecrypt($data,$key){
    if (openssl_private_decrypt($data, $r, $key)) {
       return $r;
    }
}

$keys = genPGP();
$prK = $keys[0];
$puK = $keys[1];
$data = 'abc123';
openssl_public_encrypt($data,$encrypted,$puK); 
echo prKeyDecrypt($encrypted,$prK);

I'm getting two errors, both of them similar, and they are:

Warning: openssl_public_encrypt(): key parameter is not a valid public key in test2.php on line 23

Warning: openssl_private_decrypt(): key parameter is not a valid private key in test2.php on line 14

I'm not sure what constitutes a "valid ... key." Is there a different way I'm supposed to be getting the keys? This seems accurate according to the manual and what I've read.

Thanks for the clarification. It's not really a "Secure Sockets Layer" either. I had been referring to public/private key cryptography as PGP. This is essentially PGP (particularly in the way it's implemented), I think, it's just managed differently and doesn't use the same verification/trust system (per this page). I wish there was an easier/simpler term for public/private key cryptography. — JVE999
– JVE999, Commented Jun 21, 2014 at 20:22

Jim Flood · Accepted Answer · 2014-06-21 17:42:04Z

2

You are very close. First, don't encrypt your private key with a passphrase. Second, get the public key directly from the resource. I.e.:

function genPGP0() {
    // Create the keypair
    $res=openssl_pkey_new();
    // Get private key
    openssl_pkey_export($res, $prK);
    // Get public key
    $puK = openssl_pkey_get_details($res)["key"];
    return array($prK,$puK);
}

If you want to use a passphrase (you are going to store the private key), you can use something like:

function genPGP() {
    // Create the keypair
    $res=openssl_pkey_new();
    // Get private key
    $pass = bin2hex(mcrypt_create_iv(100, MCRYPT_DEV_URANDOM));
    openssl_pkey_export($res, $prK_encrypted, $pass);
    $prK = openssl_pkey_get_private($prK_encrypted, $pass);
    // Get public key
    $puK = openssl_pkey_get_details($res)["key"];
    return array($prK,$puK);
}

answered Jun 21, 2014 at 17:42

Jim Flood

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2 Comments

JVE999 Over a year ago

As an extension of that question, if that's permissible on SO, how would I store $prK in a session variable, such as $_SESSION['prK']. The simple assignment $_SESSION['prK']=$keys[0] stores the number 0 and the same thing happens when assigning it as a reference, e.g. $_SESSION['prK']=&$keys[0].

Jim Flood Over a year ago

You should ask a new question. I don't use PHP -- I prefer Ruby, so I'm not familiar with session variables in PHP. Cheers!

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