Examples of java.security.AlgorithmParameterGenerator

java.security.AlgorithmParameterGenerator
The AlgorithmParameterGenerator class is used to generate a set of parameters to be used with a certain algorithm. Parameter generators are constructed using the getInstance factory methods (static methods that return instances of a given class).
The object that will generate the parameters can be initialized in two different ways: in an algorithm-independent manner, or in an algorithm-specific manner:
- The algorithm-independent approach uses the fact that all parameter generators share the concept of a "size" and a source of randomness. The measure of size is universally shared by all algorithm parameters, though it is interpreted differently for different algorithms. For example, in the case of parameters for the DSA algorithm, "size" corresponds to the size of the prime modulus (in bits). When using this approach, algorithm-specific parameter generation values - if any - default to some standard values, unless they can be derived from the specified size.
- The other approach initializes a parameter generator object using algorithm-specific semantics, which are represented by a set of algorithm-specific parameter generation values. To generate Diffie-Hellman system parameters, for example, the parameter generation values usually consist of the size of the prime modulus and the size of the random exponent, both specified in number of bits.
In case the client does not explicitly initialize the AlgorithmParameterGenerator (via a call to an init method), each provider must supply (and document) a default initialization. For example, the Sun provider uses a default modulus prime size of 1024 bits for the generation of DSA parameters. @author Jan Luehe @version 1.43, 04/21/06 @see AlgorithmParameters @see java.security.spec.AlgorithmParameterSpec @since 1.2

               GeneralSecurityException 
    {
        
        String s = "1.2.840.113549.3.2";
        
        AlgorithmParameterGenerator algorithmparametergenerator = AlgorithmParameterGenerator.getInstance(s);
        AlgorithmParameters algorithmparameters = algorithmparametergenerator.generateParameters();        
        ByteArrayInputStream bytearrayinputstream = new ByteArrayInputStream(algorithmparameters.getEncoded("ASN.1"));
        ASN1InputStream asn1inputstream = new ASN1InputStream(bytearrayinputstream);
        DERObject derobject = asn1inputstream.readObject();
        KeyGenerator keygenerator = KeyGenerator.getInstance(s);
        keygenerator.init(128);

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    public KeyAgreement diffieHellman(boolean side) throws IOException, GeneralSecurityException {
        KeyPair keyPair;
        PublicKey otherHalf;


        if (side) {
            AlgorithmParameterGenerator paramGen = AlgorithmParameterGenerator.getInstance("DH");
            paramGen.init(512);


            KeyPairGenerator dh = KeyPairGenerator.getInstance("DH");
            dh.initialize(paramGen.generateParameters().getParameterSpec(DHParameterSpec.class));
            keyPair = dh.generateKeyPair();


            // send a half and get a half
            writeKey(keyPair.getPublic());
            otherHalf = KeyFactory.getInstance("DH").generatePublic(readKey());

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    private void testRandom(
        int         size)
        throws Exception
    {
        AlgorithmParameterGenerator a = AlgorithmParameterGenerator.getInstance("DH", "BC");
        a.init(size, new SecureRandom());
        AlgorithmParameters params = a.generateParameters();


        byte[] encodeParams = params.getEncoded();


        AlgorithmParameters a2 = AlgorithmParameters.getInstance("DH", "BC");
        a2.init(encodeParams);

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    private void testRandom(
        int         size)
        throws Exception
    {
        AlgorithmParameterGenerator a = AlgorithmParameterGenerator.getInstance("ElGamal", "BC");
        a.init(size, new SecureRandom());
        AlgorithmParameters params = a.generateParameters();


        byte[] encodeParams = params.getEncoded();


        AlgorithmParameters a2 = AlgorithmParameters.getInstance("ElGamal", "BC");
        a2.init(encodeParams);

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    }
    
    private void testParameters()
        throws Exception
    {
        AlgorithmParameterGenerator a = AlgorithmParameterGenerator.getInstance("DSA", "BC");
        a.init(512, random);
        AlgorithmParameters params = a.generateParameters();
        
        byte[] encodeParams = params.getEncoded();
        
        AlgorithmParameters a2 = AlgorithmParameters.getInstance("DSA", "BC");
        a2.init(encodeParams);

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    private void testDSA2Parameters()
        throws Exception
    {
        byte[] seed = Hex.decode("4783081972865EA95D43318AB2EAF9C61A2FC7BBF1B772A09017BDF5A58F4FF0");


        AlgorithmParameterGenerator a = AlgorithmParameterGenerator.getInstance("DSA", "BC");
        a.init(2048, new DSATestSecureRandom(seed));
        AlgorithmParameters params = a.generateParameters();


        DSAParameterSpec dsaP = (DSAParameterSpec)params.getParameterSpec(DSAParameterSpec.class);


        if (!dsaP.getQ().equals(new BigInteger("C24ED361870B61E0D367F008F99F8A1F75525889C89DB1B673C45AF5867CB467", 16)))
        {

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    private ASN1Primitive createDERForRecipient(byte[] in, X509Certificate cert)
            throws IOException, GeneralSecurityException
    {
        String algorithm = "1.2.840.113549.3.2";
        AlgorithmParameterGenerator apg;
        KeyGenerator keygen;
        Cipher cipher;
        try
        {
            apg = AlgorithmParameterGenerator.getInstance(algorithm);
            keygen = KeyGenerator.getInstance(algorithm);
            cipher = Cipher.getInstance(algorithm);
        }
        catch (NoSuchAlgorithmException e)
        {
            // should never happen, if this happens throw IOException instead
            throw new RuntimeException("Could not find a suitable javax.crypto provider", e);
        }
        catch (NoSuchPaddingException e)
        {
            // should never happen, if this happens throw IOException instead
            throw new RuntimeException("Could not find a suitable javax.crypto provider", e);
        }


        AlgorithmParameters parameters = apg.generateParameters();


        ASN1InputStream input = new ASN1InputStream(parameters.getEncoded("ASN.1"));
        ASN1Primitive object = input.readObject();
        input.close();

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    private void testRandom(
        int         size)
        throws Exception
    {
        AlgorithmParameterGenerator a = AlgorithmParameterGenerator.getInstance("DH", "BC");
        a.init(size, new SecureRandom());
        AlgorithmParameters params = a.generateParameters();


        byte[] encodeParams = params.getEncoded();


        AlgorithmParameters a2 = AlgorithmParameters.getInstance("DH", "BC");
        a2.init(encodeParams);

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    private void testRandom(
        int         size)
        throws Exception
    {
        AlgorithmParameterGenerator a = AlgorithmParameterGenerator.getInstance("ElGamal", "BC");
        a.init(size, new SecureRandom());
        AlgorithmParameters params = a.generateParameters();


        byte[] encodeParams = params.getEncoded();


        AlgorithmParameters a2 = AlgorithmParameters.getInstance("ElGamal", "BC");
        a2.init(encodeParams);

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    }


    private void testParameters()
        throws Exception
    {
        AlgorithmParameterGenerator a = AlgorithmParameterGenerator.getInstance("DSA", "BC");
        a.init(512, random);
        AlgorithmParameters params = a.generateParameters();
        
        byte[] encodeParams = params.getEncoded();
        
        AlgorithmParameters a2 = AlgorithmParameters.getInstance("DSA", "BC");
        a2.init(encodeParams);

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