protected KeyAgreement(KeyAgreementSpi keyAgreeSpi,
    Provider provider,
    String algorithm) 
{
        this.spi = keyAgreeSpi;
        this.provider = provider;
        this.algorithm = algorithm;
        lock = null;
}

Creates a KeyAgreement object.

Parameters:

keyAgreeSpi - the delegate

provider - the provider

algorithm - the algorithm

  void chooseFirstProvider() 
{
        if (spi != null) {
            return;
        }
        synchronized (lock) {
            if (spi != null) {
                return;
            }
            if (debug != null) {
                int w = --warnCount;
                if (w  >= 0) {
                    debug.println("KeyAgreement.init() not first method "
                        + "called, disabling delayed provider selection");
                    if (w == 0) {
                        debug.println("Further warnings of this type will "
                            + "be suppressed");
                    }
                    new Exception("Call trace").printStackTrace();
                }
            }
            Exception lastException = null;
            while ((firstService != null) || serviceIterator.hasNext()) {
                Service s;
                if (firstService != null) {
                    s = firstService;
                    firstService = null;
                } else {
                    s = (Service)serviceIterator.next();
                }
                if (JceSecurity.canUseProvider(s.getProvider()) == false) {
                    continue;
                }
                try {
                    Object obj = s.newInstance(null);
                    if (obj instanceof KeyAgreementSpi == false) {
                        continue;
                    }
                    spi = (KeyAgreementSpi)obj;
                    provider = s.getProvider();
                    // not needed any more
                    firstService = null;
                    serviceIterator = null;
                    return;
                } catch (Exception e) {
                    lastException = e;
                }
            }
            ProviderException e = new ProviderException
                    ("Could not construct KeyAgreementSpi instance");
            if (lastException != null) {
                e.initCause(lastException);
            }
            throw e;
        }
}

Choose the Spi from the first provider available. Used if delayed provider selection is not possible because init() is not the first method called.

 public final Key doPhase(Key key,
    boolean lastPhase) throws InvalidKeyException, IllegalStateException 
{
        chooseFirstProvider();
        return spi.engineDoPhase(key, lastPhase);
}

Executes the next phase of this key agreement with the given key that was received from one of the other parties involved in this key agreement.

 public final byte[] generateSecret() throws IllegalStateException 
{
        chooseFirstProvider();
        return spi.engineGenerateSecret();
}

Generates the shared secret and returns it in a new buffer.

This method resets this KeyAgreement object, so that it can be reused for further key agreements. Unless this key agreement is reinitialized with one of the init methods, the same private information and algorithm parameters will be used for subsequent key agreements.

 public final SecretKey generateSecret(String algorithm) throws IllegalStateException, NoSuchAlgorithmException, InvalidKeyException 
{
        chooseFirstProvider();
        return spi.engineGenerateSecret(algorithm);
}

Creates the shared secret and returns it as a SecretKey object of the specified algorithm.

This method resets this KeyAgreement object, so that it can be reused for further key agreements. Unless this key agreement is reinitialized with one of the init methods, the same private information and algorithm parameters will be used for subsequent key agreements.

 public final int generateSecret(byte[] sharedSecret,
    int offset) throws IllegalStateException, ShortBufferException 
{
        chooseFirstProvider();
        return spi.engineGenerateSecret(sharedSecret, offset);
}

Generates the shared secret, and places it into the buffer sharedSecret, beginning at offset inclusive.

If the sharedSecret buffer is too small to hold the result, a ShortBufferException is thrown. In this case, this call should be repeated with a larger output buffer.

This method resets this KeyAgreement object, so that it can be reused for further key agreements. Unless this key agreement is reinitialized with one of the init methods, the same private information and algorithm parameters will be used for subsequent key agreements.

 public final String getAlgorithm() 
{
        return this.algorithm;
}

Returns the algorithm name of this KeyAgreement object.

This is the same name that was specified in one of the getInstance calls that created this KeyAgreement object.

 public static final KeyAgreement getInstance(String algorithm) throws NoSuchAlgorithmException 
{
        List services = GetInstance.getServices("KeyAgreement", algorithm);
        // make sure there is at least one service from a signed provider
        Iterator t = services.iterator();
        while (t.hasNext()) {
            Service s = (Service)t.next();
            if (JceSecurity.canUseProvider(s.getProvider()) == false) {
                continue;
            }
            return new KeyAgreement(s, t, algorithm);
        }
        throw new NoSuchAlgorithmException
                                ("Algorithm " + algorithm + " not available");
}

Returns a KeyAgreement object that implements the specified key agreement algorithm.

This method traverses the list of registered security Providers, starting with the most preferred Provider. A new KeyAgreement object encapsulating the KeyAgreementSpi implementation from the first Provider that supports the specified algorithm is returned.

Note that the list of registered providers may be retrieved via the Security.getProviders() method.

 public static final KeyAgreement getInstance(String algorithm,
    String provider) throws NoSuchAlgorithmException, NoSuchProviderException 
{
        Instance instance = JceSecurity.getInstance
                ("KeyAgreement", KeyAgreementSpi.class, algorithm, provider);
        return new KeyAgreement((KeyAgreementSpi)instance.impl,
                instance.provider, algorithm);
}

Returns a KeyAgreement object that implements the specified key agreement algorithm.

A new KeyAgreement object encapsulating the KeyAgreementSpi implementation from the specified provider is returned. The specified provider must be registered in the security provider list.

Note that the list of registered providers may be retrieved via the Security.getProviders() method.

 public static final KeyAgreement getInstance(String algorithm,
    Provider provider) throws NoSuchAlgorithmException 
{
        Instance instance = JceSecurity.getInstance
                ("KeyAgreement", KeyAgreementSpi.class, algorithm, provider);
        return new KeyAgreement((KeyAgreementSpi)instance.impl,
                instance.provider, algorithm);
}

Returns a KeyAgreement object that implements the specified key agreement algorithm.

A new KeyAgreement object encapsulating the KeyAgreementSpi implementation from the specified Provider object is returned. Note that the specified Provider object does not have to be registered in the provider list.

 public final Provider getProvider() 
{
        chooseFirstProvider();
        return this.provider;
}

Returns the provider of this KeyAgreement object.

 public final  void init(Key key) throws InvalidKeyException 
{
        init(key, JceSecurity.RANDOM);
}

Initializes this key agreement with the given key, which is required to contain all the algorithm parameters required for this key agreement.

If this key agreement requires any random bytes, it will get them using the SecureRandom implementation of the highest-priority installed provider as the source of randomness. (If none of the installed providers supply an implementation of SecureRandom, a system-provided source of randomness will be used.)

 public final  void init(Key key,
    SecureRandom random) throws InvalidKeyException 
{
        if (spi != null) {
            spi.engineInit(key, random);
        } else {
            try {
                chooseProvider(I_NO_PARAMS, key, null, random);
            } catch (InvalidAlgorithmParameterException e) {
                // should never occur
                throw new InvalidKeyException(e);
            }
        }
}

Initializes this key agreement with the given key and source of randomness. The given key is required to contain all the algorithm parameters required for this key agreement.

If the key agreement algorithm requires random bytes, it gets them from the given source of randomness, random. However, if the underlying algorithm implementation does not require any random bytes, random is ignored.

 public final  void init(Key key,
    AlgorithmParameterSpec params) throws InvalidKeyException, InvalidAlgorithmParameterException 
{
        init(key, params, JceSecurity.RANDOM);
}

Initializes this key agreement with the given key and set of algorithm parameters.

If this key agreement requires any random bytes, it will get them using the SecureRandom implementation of the highest-priority installed provider as the source of randomness. (If none of the installed providers supply an implementation of SecureRandom, a system-provided source of randomness will be used.)

 public final  void init(Key key,
    AlgorithmParameterSpec params,
    SecureRandom random) throws InvalidKeyException, InvalidAlgorithmParameterException 
{
        if (spi != null) {
            spi.engineInit(key, params, random);
        } else {
            chooseProvider(I_PARAMS, key, params, random);
        }
}

Initializes this key agreement with the given key, set of algorithm parameters, and source of randomness.