(PHP Extension) JWE using PBES2 Key Wrapping

Demonstrates how to create and decrypt a JWE that using PBES2 key wrapping.

This example demonstrates PBES2 with HMAC SHA-256 and A128KW wrapping. It is also possible to do the following by simply changing the "alg" parameter:

• PBES2 with HMAC SHA-384 and A192KW wrapping
• PBES2 with HMAC SHA-512 and A256KW wrapping

Note: This example requires Chilkat v9.5.0.66 or greater.

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<?php

// The version number (9_5_0) should match version of the Chilkat extension used, omitting the micro-version number.
// For example, if using Chilkat v9.5.0.48, then include as shown here:
include("chilkat_9_5_0.php");

// This requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

// Note: This example requires Chilkat v9.5.0.66 or greater.

$plaintext = 'Live long and prosper.';

$jwe = new CkJwe();

// First build the JWE Protected Header..
$jweProtHdr = new CkJsonObject();
$jweProtHdr->AppendString('alg','PBES2-HS256+A128KW');
$jweProtHdr->AppendString('enc','A128GCM');

// PBES2 requires two additional parameters:
// 1) A random salt parameter ("p2s") containing 8 or more bytes in base64url format.
// 2) An iteration count parameter ("p2c").  A minimum count of 1000 is recommended.
//    The iteration count is intended to make the PBES2 computation more expensive (time consuming)
//    to prevent brute-force attacks.
$prng = new CkPrng();
$jweProtHdr->AppendString('p2s',$prng->genRandom(16,'base64url'));
$jweProtHdr->AppendString('p2c','1000');

print 'JWE Protected Header: ' . $jweProtHdr->emit() . "\n";
print '--' . "\n";

// Don't forget to actually provide the protected header to the JWE object:
$jwe->SetProtectedHeader($jweProtHdr);

// Set the PBES2 password
$recipientIndex = 0;
$jwe->SetPassword($recipientIndex,'top secret');

// Encrypt and return the JWE:
$strJwe = $jwe->encrypt($plaintext,'utf-8');
if ($jwe->get_LastMethodSuccess() != true) {
    print $jwe->lastErrorText() . "\n";
    exit;
}

// Show the JWE we just created:
print $strJwe . "\n";

// Decrypt the JWE.
$jwe2 = new CkJwe();
$success = $jwe2->LoadJwe($strJwe);
if ($success != true) {
    print $jwe2->lastErrorText() . "\n";
    exit;
}

// Set the PBES2 password
$jwe2->SetPassword($recipientIndex,'top secret');

// Decrypt.
$originalPlaintext = $jwe2->decrypt(0,'utf-8');
if ($jwe2->get_LastMethodSuccess() != true) {
    print $jwe2->lastErrorText() . "\n";
    exit;
}

print 'original text: ' . "\n";
print $originalPlaintext . "\n";

// Sample output:

// JWE Protected Header: {"alg":"PBES2-HS256+A128KW","enc":"A128GCM","p2s":"z39rTEfRy1T1Yn_D1mZRlg","p2c":"1000"}
// --
// eyJhbGciOiJQQkVTMi1IUzI1NitBMTI4S1ciLCJlbmMiOiJBMTI4R0NNIiwicDJzIjoiejM5clRFZlJ5MVQxWW5fRDFtWlJsZyIsInAyYyI6IjEwMDAifQ.koYt6PrFmYwcwdcT7ZcvXHA1d-Xez5h4.luGlbvEnZp-7IsBOj42Yhw.YMTcfLf8Qe4zazozGV2OAu3cUdQ8Kg.rWub47ESWkc6IqZJTvSTmg
// original text: 
// Live long and prosper.

?>