(PHP Extension) JWE using A256GCMKW

This example demonstrates creating a JCE with AES GCM key wrap.

Chilkat PHP Downloads PHP Extension for Windows, Linux, MacOS, Alpine Linux, Solaris

<?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.

$plaintext = 'My text to enrypt';

$jwe = new CkJwe();

// First build the JWE Protected Header: 

//         {
//             "alg": "A256GCMKW",
//             "kid": "18ec08e1-bfa9-4d95-b205-2b4dd1d4321d",
//             "tag": "kfPduVQ3T3H6vnewt--ksw",
//             "iv": "KkYT0GX_2jHlfqN_",
//             "enc": "A128CBC-HS256"
//         }

$jweProtHdr = new CkJsonObject();
$jweProtHdr->AppendString('alg','A256GCMKW');
// kid is optional
$jweProtHdr->AppendString('kid','18ec08e1-bfa9-4d95-b205-2b4dd1d4321d');
// tag is optional
$jweProtHdr->AppendString('tag','kfPduVQ3T3H6vnewt--ksw');
$jweProtHdr->AppendString('enc','A256GCM');
// the iv should be 16 random chars.
$prng = new CkPrng();
$jweProtHdr->AppendString('iv',$prng->randomString(16,true,true,true));
$jwe->SetProtectedHeader($jweProtHdr);

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

// Given that we have 256-bit AES, our key should be 32 bytes.
// The ascii string here is 32 bytes, therefore the 2nd arg is "ascii" to use these
// ascii chars directly as the key.
$aesWrappingKey = '2baf4f730f5e4542b428593ef9cceb0e';
$jwe->SetWrappingKey(0,$aesWrappingKey,'ascii');

// 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 that was just produced.
// 1) Load the JWE.
// 2) Set the AES wrapping key.
// 3) Decrypt.
$jwe2 = new CkJwe();
$success = $jwe2->LoadJwe($strJwe);
if ($success != true) {
    print $jwe2->lastErrorText() . "\n";
    exit;
}

// Set the AES wrap key.  Important to use "ascii"
$jwe2->SetWrappingKey(0,$aesWrappingKey,'ascii');

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

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

?>