Usage

Additional to this Wiki entry, please consult also the project's JavaDoc.

Keys

liJense uses currently RSA keys with the size of 4096 bit. Neither the key algorithm nor the key size can currently be changed via the API. Please visit the JavaDocs for more detailed information on the methods of KeyUtil.

Generating New Keys

Generating a new pair of private and public keys is quite easy. You can use KeyUtil.generateNewKeyPair() to do this. The currently used random generator to create the key pair is SHA1PRNG.

KeyPair keyPair = KeyUtil.generateNewKeyPair( );
PrivateKey privateKey = keyPair.getPrivate( );
PublicKey publicKey = keyPair.getPublic( );

If you want to generate the keys yourself (for instance, if you want to use an own random generator), you can do so and still use them with liJense, as long as the resulting keys are 4096 Bit RSA keys.

Saving and Loading Keys

The KeyUtil class provides various methods to store and retrieve keys. In order to save a private or public key to a file, you can use KeyUtil.saveKeyToFile(Key,File).

KeyUtil.saveKeyToFile( privateKey, new File( "key.private" ) );
KeyUtil.saveKeyToFile( publicKey, new File( "key.public" ) );

If you want to store the keys in a database, you might want to consider to use the getEncoded() methods of the keys instead.

byte[] binaryPrivateKey = privateKey.getEncoded();

In order to load keys, liJense provides three methods for the private and the public key respectively. Keys can be loaded from a file, an input stream (useful if the public key is within your JAR file) or from an array containing binary data (useful if the key is loaded from a database blob).

PrivateKey privateKey = KeyUtil.loadPrivateKeyFromFile( new File( "key.private" ) );
PublicKey publicKey = KeyUtil.loadPublicKeyFromArray( binaryPublicKey );

Calculating and Verifying Fingerprints

When you ship your application or library with the public key to verify a given license, you should also check the fingerprint of the public key. This makes sure that the public key cannot simply be exchanged from your JAR file. The methods KeyUtil.calculateFingerprint(PublicKey) and KeyUtil.calculateFingerprint(byte[]) allow you to calculate the fingerprint of the public key, which is currently the SHA-512 hash of the key.

byte[] fingerprint = KeyUtil.calculateFingerprint( publicKey );

To verify the fingerprint, you can use the method KeyUtil.isFingerprintValid(PublicKey, byte[]). However, you can also use the fingerprint when loading a license to verify the fingerprint implicitly. It is recommended to store the fingerprint directly in a constant expression in the Java code.

private static final byte[] FINGERPRINT = new byte[] { //
			-96, -95, 56, -80, 0, -5, 49, -82, //
			-34, 44, -112, -20, -110, -38, 21, 28, //
			72, 88, 96, 37, -24, 48, -122, 34, //
			-12, 46, -109, 40, -4, -46, 105, -49, //
			117, 59, 30, 124, 4, -67, -107, -90, //
			-62, 115, 110, -102, 127, -126, 119, 78, //
			-75, 46, 30, 101, -53, -49, 59, 71, //
			-97, 54, -58, -38, 31, 102, 58, -122 };

...

if ( KeyUtil.isFingerprintValid( publicKey, FINGERPRINT ) ) {
    ...
}

Licenses

liJense uses currently SHA-512 with RSA for the signature of the license. Currently this cannot be changed via the API. Please visit the JavaDocs for more detailed information on the methods of LicenseUtil.

Creating Licenses

In order to create a license with liJense, you use an instance of ModifiableLicense, which is simply a Properties object with some additional methods. You can add arbitrary key/value pairs here. Some common use cases are:

• The edition (e.g., enterprise edition)
• Active features and modules (e.g., LDAP)
• Limitations (e.g., maximal number of HTTP connections)
• Expiration date

Various setValue methods in _ModifiableLicense allow you to set values for each primitive datatype. Additionally, there is the setExpirationDate(Date) method to set the expiration date of the license. If left empty, the license never expires.

ModifiableLicense license = new ModifiableLicense( );
license.setValue( "edition", "Enterprise Edition" );
license.setValue( "createdAt", new Date( ) );
license.setValue( "feature.ldap.active", true );
license.setValue( "feature.http.maxConnections", 100 );
license.setExpirationDate( expirationDate );