(PHP Extension) JWE using AES Key Wrap and AES_128_CBC_HMAC_SHA_256

This example duplicates the example A.3 in RFC 7516 for JSON Web Encryption (JWE).

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

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.

// 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: {"alg":"A128KW","enc":"A128CBC-HS256"}
$jweProtHdr = new CkJsonObject();
$jweProtHdr->AppendString('alg','A128KW');
$jweProtHdr->AppendString('enc','A128CBC-HS256');
$jwe->SetProtectedHeader($jweProtHdr);

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

// The example A.3 in RFC 7516 uses the following 128-bit AES key,
// specified in JWK (JSON Web Key) format:
//      {"kty":"oct",
//       "k":"GawgguFyGrWKav7AX4VKUg"
//      }
// This is just a way of saying: The key type ("kty") is 
// a bunch of octets ("k") in base64url encoding.
// We can simply set the AES wrapping key like this:
$aesWrappingKey = 'GawgguFyGrWKav7AX4VKUg';
$jwe->SetWrappingKey(0,$aesWrappingKey,'base64url');

// 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.
$jwe2->SetWrappingKey(0,$aesWrappingKey,'base64url');

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

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

// ---------------------------------------------------------------------------------
// It should also be possible to decrypt the JWE as shown in RFC 7516, Appendix A.3.7
// because it was produced using the same AES Wrap key.

$sbJwe = new CkStringBuilder();
$sbJwe->Append('eyJhbGciOiJBMTI4S1ciLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0.');
$sbJwe->Append('6KB707dM9YTIgHtLvtgWQ8mKwboJW3of9locizkDTHzBC2IlrT1oOQ.');
$sbJwe->Append('AxY8DCtDaGlsbGljb3RoZQ.');
$sbJwe->Append('KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY.');
$sbJwe->Append('U0m_YmjN04DJvceFICbCVQ');

$success = $jwe2->LoadJweSb($sbJwe);
if ($success != true) {
    print $jwe2->lastErrorText() . "\n";
    exit;
}

$jwe2->SetWrappingKey(0,$aesWrappingKey,'base64url');

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

print $originalPlaintext . "\n";

?>