Key Management (JWK)

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You can create a JWK object using two static methods:

  • JWK::create(array $values): creates a JWK using direct values.

  • JWK::createFromJson(string $json): creates a JWK using a JSON object.

Hereafter all methods available for a JWK object. The variable $jwk is a valid JWK object.

<?php
// Check if the key has a parameter.
$jwk->has('kty');
// Retrieve the key parameter.
$jwk->get('kty');
// Retrieve all key parameters.
$jwk->all();
// Calculate the thumbprint of the key. Acceptable hash algorithms are those returned by the PHP function "hash_algos".
$jwk->thumbprint('sha256');
// If the key is a private key (RSA, EC, OKP), it can be converted into public:
$public_key = $jwk->toPublic();
// The JWK object can be serialized into JSON
json_encode($jwk);

Please note a JWK object is an immutable object

Generate A New Key

This framework is able to create private and public keys easily using the JWKFactory. It is available in the web-token/jwt-key-mgmt component.

composer require web-token/jwt-key-mgmt

4 types of keys are supported:

  • Symmetric Key:

    • oct: octet string

  • Asymmetric Key:

    • RSA: RSA key pair

    • EC : Elliptic Curve key pair

    • OKP: Octet key pair

Note: for the none algorithm, the framework needs a key of type none. This is a specific key type that must only be used with this algorithm.

Octet String

The following example will show you how to create an oct key.

Additional parameters will be set to limit the scope of this key (e.g. signature/verification only with the HS256 algorithm).

<?php
use Jose\Component\KeyManagement\JWKFactory;
$key = JWKFactory::createOctKey(
1024, // Size in bits of the key. We recommend at least 128 bits.
[
'alg' => 'HS256', // This key must only be used with the HS256 algorithm
'use' => 'sig' // This key is used for signature/verification operations only
]
);

The following feature was introduced in version 1.1.

If you already have a shared secret, you can use it to create an oct key:

<?php
use Jose\Component\KeyManagement\JWKFactory;
$jwk = JWKFactory::createFromSecret(
'My Secret Key', // The shared secret
[ // Optional additional members
'alg' => 'HS256',
'use' => 'sig'
]
);

RSA Key Pair

The following example will show you how to create a RSA key.

The key size must be of 384 bits at least.

<?php
use Jose\Component\KeyManagement\JWKFactory;
$private_key = JWKFactory::createRSAKey(
4096, // Size in bits of the key. We recommend at least 2048 bits.
[
'alg' => 'RSA-OAEP-256', // This key must only be used with the RSA-OAEP-256 algorithm
'use' => 'enc' // This key is used for encryption/decryption operations only
]);

Elliptic Curve Key Pair

The following example will show you how to create a EC key.

<?php
use Jose\Component\KeyManagement\JWKFactory;
$key = JWKFactory::createECKey('P-256');

The supported curves are:

  • P-256

  • P-384

  • P-521 (note that this is 521 and not 512)

Octet Key Pair

The following example will show you how to create a OKP key.

<?php
use Jose\Component\KeyManagement\JWKFactory;
$key = JWKFactory::createOKPKey('X25519');

The supported curves are:

  • Ed25519 for signature/verification only

  • X25519 for encryption/decryption only

None Key

The none key type is a special type used only for the none algorithm.

<?php
use Jose\Component\KeyManagement\JWKFactory;
$key = JWKFactory::createNoneKey();

Create Key From External Sources

From Values

In case you already have key values, you can create a key by passing those values as an argument:

<?php
use Jose\Component\KeyManagement\JWKFactory;
$key = JWKFactory::createFromValues([
'kid' => '71ee230371d19630bc17fb90ccf20ae632ad8cf8',
'kty' => 'RSA',
'alg' => 'RS256',
'use' => 'sig',
'n' => 'vnMTRCMvsS04M1yaKR112aB8RxOkWHFixZO68wCRlVLxK4ugckXVD_Ebcq-kms1T2XpoWntVfBuX40r2GvcD9UsTFt_MZlgd1xyGwGV6U_tfQUll5mKxCPjr60h83LXKJ_zmLXIqkV8tAoIg78a5VRWoms_0Bn09DKT3-RBWFjk=',
'e' => 'AQAB',
]);

From A Key File

You can convert a PKCS#1 or PKCS#8 key file into a JWK. The following method supports PEM and DER formats. Encrypted keys are also supported.

<?php
use Jose\Component\KeyManagement\JWKFactory;
$key = JWKFactory::createFromKeyFile(
'/path/to/my/key/file.pem', // The filename
'Secret', // Secret if the key is encrypted
[
'use' => 'sig', // Additional parameters
]
);

From A PKCS#12 Certificate

You can convert a PKCS#12 Certificate into a JWK. Encrypted certificates are also supported.

<?php
use Jose\Component\KeyManagement\JWKFactory;
$key = JWKFactory::createFromPKCS12CertificateFile(
'/path/to/my/key/file.p12', // The filename
'Secret', // Secret if the key is encrypted
[
'use' => 'sig', // Additional parameters
]
);

From A X.509 Certificate

You can convert a X.509 Certificate into a JWK.

<?php
use Jose\Component\KeyManagement\JWKFactory;
$key = JWKFactory::createFromCertificateFile(
'/path/to/my/key/file.crt', // The filename
[
'use' => 'sig', // Additional parameters
]
);

Please note that X.509 certificates only contains public keys.