This class provides an API for generating secret keys for symmetric cryptography. It is similar to java.security.KeyPairGenerator, which generates public/private key pairs for asymmetric or public-key cryptography. KeyGenerator is algorithm-independent and provider-based, so you must obtain a KeyGenerator instance by calling one of the static getInstance( ) factory methods and specifying the name of the cryptographic algorithm for which a key is desired and, optionally, the name of the security provider whose key-generation implementation is to be used. In Java 5.0 the "SunJCE" provider includes KeyGenerator implementations algorithms with the following names:

DESede

HmacMD5

HmacSHA1

HmacSHA256

Once you have obtained a KeyGenerator, you initialize it with the init( ) method. You can provide a java.security.spec.AlgorithmParameterSpec object to provide algorithm-specific initialization parameters or simply specify the desired size (in bits) of the key to be generated. In either case, you can also specify a source of randomness in the form of a SecureRandom object. If you do not specify a SecureRandom, the KeyGenerator instantiates one of its own. None of the algorithms supported by the "SunJCE" provider require algorithm-specific parameters.

After calling getInstance( ) to obtain a KeyGenerator and init( ) to initialize it, simply call generateKey( ) to create a new SecretKey. Remember that the SecretKey must be kept secret. Take precautions when storing or transmitting the key, so that it does not fall into the wrong hands. You may want to use a java.security.KeyStore object to store the key in a password-protected form.

public class KeyGenerator {
// Protected Constructors
     protected KeyGenerator(KeyGeneratorSpi keyGenSpi, java.security.Provider provider, 
        String algorithm);  
// Public Class Methods
     public static final KeyGenerator getInstance(String algorithm) 
        throws java.security.NoSuchAlgorithmException;  
     public static final KeyGenerator getInstance(String algorithm, 
        java.security.Provider provider) throws java.security.NoSuchAlgorithmException;  
     public static final KeyGenerator getInstance(String algorithm, 
        String provider) throws java.security.NoSuchAlgorithmException, 
        java.security.NoSuchProviderException;  
// Public Instance Methods
     public final SecretKey generateKey( );  
     public final String getAlgorithm( );  
     public final java.security.Provider getProvider( );  
     public final void init(int keysize);  
     public final void init(java.security.spec.AlgorithmParameterSpec params) 
        throws java.security.InvalidAlgorithmParameterException;  
     public final void init(java.security.SecureRandom random);  
     public final void init(int keysize, java.security.SecureRandom random);  
     public final void init(java.security.spec.AlgorithmParameterSpec params, 
        java.security.SecureRandom random) 
        throws java.security.InvalidAlgorithmParameterException;  
}