(PHP Extension) JWE using RSAES-OAEP and AES GCM

This example duplicates the example A.1 in RFC 7516 for JSON Web Encryption (JWE).

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 = 'The true sign of intelligence is not knowledge but imagination.';

// ---------------------------------
// A.1.1 JOSE Header
// First build the JWE Protected Header.
// We want to build this: {"alg":"RSA-OAEP","enc":"A256GCM"}
$jweProtHdr = new CkJsonObject();
$jweProtHdr->AppendString('alg','RSA-OAEP');
$jweProtHdr->AppendString('enc','A256GCM');
print 'JWE Protected Header: ' . $jweProtHdr->emit() . "\n";
print '--' . "\n";

// ---------------------------------
// A.1.2 Content Encryption Key
// Note: Chilkat automatically generates the random CEK internally.
// The application does not need to explicitly take this step.

// ---------------------------------
// A.1.3.  Key Encryption
// The application should load an RSA private key from any format.
// However, the application does not need to explicitly construct the JWE Encrypted Key.
// Chilkat automatically does it internally.
// The design of the Chilkat JWE API is to allow the application to create the JWE
// after specifying the inputs.  (This is in contrast to forcing the application developer
// to painstakingly go through each step of the JWE construction process.)

// The specific RSA key used in the A.1 example is the following JWK:
$sbJwk = new CkStringBuilder();
$sbJwk->Append('{\'kty\': \'RSA\',');
$sbJwk->Append('\'n\': \'oahUIoWw0K0usKNuOR6H4wkf4oBUXHTxRvgb48E-BVvxkeDNjbC4he8rUW');
$sbJwk->Append('cJoZmds2h7M70imEVhRU5djINXtqllXI4DFqcI1DgjT9LewND8MW2Krf3S');
$sbJwk->Append('psk_ZkoFnilakGygTwpZ3uesH-PFABNIUYpOiN15dsQRkgr0vEhxN92i2a');
$sbJwk->Append('sbOenSZeyaxziK72UwxrrKoExv6kc5twXTq4h-QChLOln0_mtUZwfsRaMS');
$sbJwk->Append('tPs6mS6XrgxnxbWhojf663tuEQueGC-FCMfra36C9knDFGzKsNa7LZK2dj');
$sbJwk->Append('YgyD3JR_MB_4NUJW_TqOQtwHYbxevoJArm-L5StowjzGy-_bq6Gw\',');
$sbJwk->Append('\'e\': \'AQAB\',');
$sbJwk->Append('\'d\': \'kLdtIj6GbDks_ApCSTYQtelcNttlKiOyPzMrXHeI-yk1F7-kpDxY4-WY5N');
$sbJwk->Append('WV5KntaEeXS1j82E375xxhWMHXyvjYecPT9fpwR_M9gV8n9Hrh2anTpTD9');
$sbJwk->Append('3Dt62ypW3yDsJzBnTnrYu1iwWRgBKrEYY46qAZIrA2xAwnm2X7uGR1hghk');
$sbJwk->Append('qDp0Vqj3kbSCz1XyfCs6_LehBwtxHIyh8Ripy40p24moOAbgxVw3rxT_vl');
$sbJwk->Append('t3UVe4WO3JkJOzlpUf-KTVI2Ptgm-dARxTEtE-id-4OJr0h-K-VFs3VSnd');
$sbJwk->Append('VTIznSxfyrj8ILL6MG_Uv8YAu7VILSB3lOW085-4qE3DzgrTjgyQ\',');
$sbJwk->Append('\'p\': \'1r52Xk46c-LsfB5P442p7atdPUrxQSy4mti_tZI3Mgf2EuFVbUoDBvaRQ-');
$sbJwk->Append('SWxkbkmoEzL7JXroSBjSrK3YIQgYdMgyAEPTPjXv_hI2_1eTSPVZfzL0lf');
$sbJwk->Append('fNn03IXqWF5MDFuoUYE0hzb2vhrlN_rKrbfDIwUbTrjjgieRbwC6Cl0\',');
$sbJwk->Append('\'q\': \'wLb35x7hmQWZsWJmB_vle87ihgZ19S8lBEROLIsZG4ayZVe9Hi9gDVCOBm');
$sbJwk->Append('UDdaDYVTSNx_8Fyw1YYa9XGrGnDew00J28cRUoeBB_jKI1oma0Orv1T9aX');
$sbJwk->Append('IWxKwd4gvxFImOWr3QRL9KEBRzk2RatUBnmDZJTIAfwTs0g68UZHvtc\',');
$sbJwk->Append('\'dp\': \'ZK-YwE7diUh0qR1tR7w8WHtolDx3MZ_OTowiFvgfeQ3SiresXjm9gZ5KL');
$sbJwk->Append('hMXvo-uz-KUJWDxS5pFQ_M0evdo1dKiRTjVw_x4NyqyXPM5nULPkcpU827');
$sbJwk->Append('rnpZzAJKpdhWAgqrXGKAECQH0Xt4taznjnd_zVpAmZZq60WPMBMfKcuE\',');
$sbJwk->Append('\'dq\': \'Dq0gfgJ1DdFGXiLvQEZnuKEN0UUmsJBxkjydc3j4ZYdBiMRAy86x0vHCj');
$sbJwk->Append('ywcMlYYg4yoC4YZa9hNVcsjqA3FeiL19rk8g6Qn29Tt0cj8qqyFpz9vNDB');
$sbJwk->Append('UfCAiJVeESOjJDZPYHdHY8v1b-o-Z2X5tvLx-TCekf7oxyeKDUqKWjis\',');
$sbJwk->Append('\'qi\': \'VIMpMYbPf47dT1w_zDUXfPimsSegnMOA1zTaX7aGk_8urY6R8-ZW1FxU7');
$sbJwk->Append('AlWAyLWybqq6t16VFd7hQd0y6flUK4SlOydB61gwanOsXGOAOv82cHq0E3');
$sbJwk->Append('eL4HrtZkUuKvnPrMnsUUFlfUdybVzxyjz9JF_XyaY14ardLSjf4L_FNY\'}');

// Load this JWK into a Chilkat private key object.
$rsaPrivKey = new CkPrivateKey();
$success = $rsaPrivKey->LoadJwk($sbJwk->getAsString());
if ($success != true) {
    print $rsaPrivKey->lastErrorText() . "\n";
    exit;
}

// The public key is used to encrypt (i.e. create the JWE), 
// and the private key is used to decrypt.
// The RSA public key is simply a subset of the private key.  The RSA public key
// is composed of the "n" and "e" members shown above.  These are also known as the
// modulus and exponent.
// We can simply get the public key object from the private key object
// rsaPubKey is a CkPublicKey
$rsaPubKey = $rsaPrivKey->GetPublicKey();

// ---------------------------------
// A.1.4.  Initialization Vector
// Chilkat automatically generates the necessary random IV internally.  
// The application does not need to do this explicitly.

// ---------------------------------
// A.1.5.  Additional Authenticated Data
// The Additional Authenticated Data encryption parameter is
// ASCII(BASE64URL(UTF8(JWE Protected Header))).
// Again, Chilkat automatically takes care of this internally.
// The application does not need to explicitly take this step.

// ---------------------------------
// A.1.6.  Content Encryption
// Again... this step is handled by Chilkat internally.

// ---------------------------------
// A.1.7.  Complete Representation
// The application need only call the Encrypt, EncryptSb, or EncryptBd method
// return the fully assembled JWE.  
// The final representation in the Compact Serialization 
// is the string BASE64URL(UTF8(JWE Protected Header)) || '.' ||
// BASE64URL(JWE Encrypted Key) || '.' || BASE64URL(JWE Initialization
// Vector) || '.' || BASE64URL(JWE Ciphertext) || '.' || BASE64URL(JWE
// Authentication Tag).

$jwe = new CkJwe();
$jwe->SetProtectedHeader($jweProtHdr);
$jwe->SetPublicKey(0,$rsaPubKey);

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

// Note: The RSA OAEP algorithm uses random padding bytes internally.
// Therefore, the results will appear different each time -- even if the
// identical plaintext is encrypted with the identical RSA key. 
// (Do not expect the appearance of the results to be the same as what
// is published in the RFC.  However, what is published in the RFC *should*
// be decryptable using the code that follows.)
print $strJwe . "\n";

// Let's decrypt the JWE that was just produced.
// Do the following to decrypt a JWE:
// 1) Load the JWE.
// 2) Set the private key for decryption.
// 3) Decrypt.
$jwe2 = new CkJwe();
$success = $jwe2->LoadJwe($strJwe);
if ($success != true) {
    print $jwe2->lastErrorText() . "\n";
    exit;
}

// Provide the RSA private key for decryption.
// (The JWE was encrypted for a single recipient at index 0.)
$jwe2->SetPrivateKey(0,$rsaPrivKey);

// 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.1.7
// because it was produced using the same RSA key.

$sbJwe = new CkStringBuilder();
$sbJwe->Append('eyJhbGciOiJSU0EtT0FFUCIsImVuYyI6IkEyNTZHQ00ifQ.');
$sbJwe->Append('OKOawDo13gRp2ojaHV7LFpZcgV7T6DVZKTyKOMTYUmKoTCVJRgckCL9kiMT03JGe');
$sbJwe->Append('ipsEdY3mx_etLbbWSrFr05kLzcSr4qKAq7YN7e9jwQRb23nfa6c9d-StnImGyFDb');
$sbJwe->Append('Sv04uVuxIp5Zms1gNxKKK2Da14B8S4rzVRltdYwam_lDp5XnZAYpQdb76FdIKLaV');
$sbJwe->Append('mqgfwX7XWRxv2322i-vDxRfqNzo_tETKzpVLzfiwQyeyPGLBIO56YJ7eObdv0je8');
$sbJwe->Append('1860ppamavo35UgoRdbYaBcoh9QcfylQr66oc6vFWXRcZ_ZT2LawVCWTIy3brGPi');
$sbJwe->Append('6UklfCpIMfIjf7iGdXKHzg.');
$sbJwe->Append('48V1_ALb6US04U3b.');
$sbJwe->Append('5eym8TW_c8SuK0ltJ3rpYIzOeDQz7TALvtu6UG9oMo4vpzs9tX_EFShS8iB7j6ji');
$sbJwe->Append('SdiwkIr3ajwQzaBtQD_A.');
$sbJwe->Append('XFBoMYUZodetZdvTiFvSkQ');

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

// Provide the RSA private key for decryption.
$jwe2->SetPrivateKey(0,$rsaPrivKey);

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

print $originalPlaintext . "\n";

?>