cipher.java

jpeg2000编解码

            throw new IllegalArgumentException("IJCE does not support ciphers for which implPadding == true");

        this.implBuffering = implBuffering;
        this.provider = provider;
    }

    /**
     * This constructor is identical to the previous one (with arguments
     * boolean, boolean, String), except that it does not have the redundant
     * <i>implPadding</i> parameter, and also allows the algorithm name
     * to be specified.
     * <p>
     * <strong><a href="../guide/ijce/JCEDifferences.html">This constructor
     * is not supported in JavaSoft's version of JCE.</a></strong>
     *
     * @param  implBuffering    if true, this argument indicates that data
     *                          will always be passed from update/crypt to
     *                          engineUpdate/engineCrypt without modification.
     * @param  provider         the name of the provider of the underlying
     *                          cryptographic engine.
     * @param  algorithm        the name of this algorithm (optionally with
     *                          mode and padding, separated by '/'), as it is
     *                          configured in the properties file.
     */
    protected Cipher(boolean implBuffering, String provider, String algorithm) {
        super("Cipher");
        this.implBuffering = implBuffering;
        this.provider = provider;
        parseAlgorithm(algorithm);
    }

    private void parseAlgorithm(String algorithm) {
        int p = algorithm.indexOf('/');
        if (p == -1)
            cipherName = algorithm;
        else {            // "cipher/..."
            cipherName = algorithm.substring(0, p);
            int q = algorithm.indexOf('/', p+1);
            if (q == -1)  // "cipher/mode"
                modeName = algorithm.substring(p+1);
            else {        // "cipher/mode/padding"
                modeName = algorithm.substring(p+1, q);
                paddingName = algorithm.substring(q+1);
            }
        }
    }

    private void
    setNames(String cipherName, String modeName, String paddingName, String provider) {
        if (this.cipherName == null)  this.cipherName = cipherName;
        if (this.modeName == null)    this.modeName = modeName;
        if (this.paddingName == null) this.paddingName = paddingName;
        if (this.provider == null)    this.provider = provider;
    }

    /**
     * Returns the object implementing padding for this cipher, or null if
     * there is no such object.
     */
    protected final PaddingScheme getPaddingScheme() {
        return padding;
    }

    /**
     * Generates a Cipher object that implements the given algorithm. If the
     * default provider package contains a class implementing the algorithm,
     * an instance of that class is returned. If it is not available in the
     * default package, other packages are searched.
     * <p>
     * Any of the following formats can be used for the algorithm name:
     * <p>
     * <dl>
     *   <dt> cipher "/" mode "/" padding
     *     <dd> all algorithm components - cipher, mode, and padding -
     *          are specified (these may be aliases).
     *   <dt> cipher "/" mode
     *     <dd> the padding is assumed to be "NONE".
     *   <dt> cipher
     *     <dd> the mode is assumed to be "ECB", and the padding to be "NONE".
     * </dl>
     * <p>
     * See <a href="../guide/ijce/Algorithms.html#Cipher">
     * <cite>International JCE Standard Algorithm Names</cite></a> for a list
     * of Cipher algorithm names.
     *
     * @param  algorithm    the algorithm name, as described above.
     * @return the new Cipher object, in the UNINITIALIZED state.
     * @exception NoSuchAlgorithmException if the algorithm is
     *                      not available from any provider.
     */
    public static Cipher getInstance(String algorithm)
    throws NoSuchAlgorithmException {
        try { return getInstance(algorithm, null); }
        catch (NoSuchProviderException e) {
            throw new NoSuchAlgorithmException(e.getMessage());
        }
    }

    /**
     * Generates a Cipher object that implements the given cipher, from
     * the given provider. The format of the cipher specification is as
     * described for <code>getInstance(String algorithm)</code>.
     * <p>
     * If the algorithm is implemented using more than one component
     * (cipher, mode, and padding scheme), all of them must come from the
     * given provider. More flexibility can be obtained by using the
     * <code>getInstance(Cipher, Mode, PaddingScheme)</code> factory method.
     * For example, to request "DES" from the SUN provider, "CBC" from the
     * Cryptix provider, and "PKCS#5" from any provider, use:
     * <pre>
     *    Cipher.getInstance(
     *        Cipher.getInstance("DES", "SUN"),
     *        Mode.getInstance("CBC", "Cryptix"),
     *        PaddingScheme.getInstance("PKCS#5")
     *    )
     * </pre>
     * <p>
     * See <a href="../guide/ijce/Algorithms.html#Cipher">
     * <cite>International JCE Standard Algorithm Names</cite></a> for a list
     * of Cipher algorithm names.
     *
     * @param  algorithm    the cipher specification.
     * @return the new Cipher object, in the UNINITIALIZED state.
     * @exception NoSuchAlgorithmException if the algorithm is not
     *                      available from the provider.
     * @exception NoSuchProviderException if the provider is not
     *                      available in the environment.
     */
    public static Cipher getInstance(String algorithm, String provider)
    throws NoSuchAlgorithmException, NoSuchProviderException {
        if (algorithm == null)
            throw new NullPointerException("algorithm == null");

        // parse the algorithm spec
        String cipherName = algorithm;
        String modeName = "ECB";
        String paddingName = "NONE";

        int p = algorithm.indexOf('/');
        if (p != -1) {      // "cipher/..."
            cipherName = algorithm.substring(0, p);
            int q = algorithm.indexOf('/', p+1);
            if (q == -1)  // "cipher/mode"
                modeName = algorithm.substring(p+1);
            else {        // "cipher/mode/padding"
                modeName = algorithm.substring(p+1, q);
                paddingName = algorithm.substring(q+1);
            }
        }
        return getInstance(cipherName, modeName, paddingName, provider);
    }

    /**
     * Generates a Cipher object implementing the specified algorithm, mode,
     * and padding from the specified provider.
     *
     * @param  algorithmName    the string name of the algorithm.
     * @param  modeName         the string name of the mode.
     * @param  paddingName      the string name of the padding scheme.
     * @return the new Cipher object, in the UNINITIALIZED state.
     * @exception NoSuchAlgorithmException if the algorithm is not
     *                          available from the provider.
     * @exception NoSuchProviderException if the provider is not
     *                          available in the environment.
     */
    private static Cipher
    getInstance(String cipherName, String modeName, String paddingName, String provider)
    throws NoSuchAlgorithmException, NoSuchProviderException {

if (DEBUG && debuglevel >= 3) debug("Entered getInstance(\"" + cipherName + "\", \"" +
    modeName + "\", \"" + paddingName + "\", \"" + provider + "\")");

        // Note: we use IJCE.getImplementation, not Security.getImpl, below,
        // because Security.getImpl is not guaranteed to exist in all
        // implementations of JCA.
        cipherName = IJCE.getStandardName(cipherName, "Cipher");
        modeName = IJCE.getStandardName(modeName, "Mode");
        paddingName = IJCE.getStandardName(paddingName, "PaddingScheme");

        Cipher result, nested = null;
        PaddingScheme padding = null;
        try {   // first check for a combined "cipher/mode/padding".
            result = (Cipher) (IJCE.getImplementation(cipherName + "/" + modeName +
                "/" + paddingName, provider, "Cipher"));
        } catch (NoSuchAlgorithmException e) {
            if (modeName.equals("ECB"))
                result = (Cipher) (IJCE.getImplementation(cipherName, provider,
                    "Cipher"));
            else {
                try {   // check for "cipher/mode".
                    result = (Cipher) (IJCE.getImplementation(cipherName + "/" +
                        modeName, provider, "Cipher"));
                } catch (NoSuchAlgorithmException e2) {
                    // otherwise, the object returned to the user will be a
                    // subclass of Mode.
                    nested = (Cipher) (IJCE.getImplementation(cipherName, provider,
                        "Cipher"));
                    nested.setNames(cipherName, "ECB", "NONE", provider);
                    result = (Cipher) (IJCE.getImplementation(modeName, provider,
                        "Mode"));
                }
            }
            if (!paddingName.equals("NONE")) {
                padding = (PaddingScheme) (IJCE.getImplementation(paddingName,
                    provider, "PaddingScheme"));
            }
        }
        result.setNames(cipherName, modeName, paddingName, provider);

        // We used to set the input block size for the padding scheme here, but
        // it might not be valid until the cipher is initialized, so set it in
        // initEncrypt/Decrypt instead.

        if (nested != null) ((Mode) result).engineSetCipher(nested);
        if (padding != null) result.engineSetPaddingScheme(padding);

if (DEBUG && debuglevel >= 3) debug("Created cipher [1]: " + result);

        return result;
    }

    /**
     * Generates a new Cipher object by composing the given Cipher, Mode and
     * PaddingScheme objects. <i>mode</i> may be null (indicating ECB),
     * and <i>padding</i> may be null (indicating NONE).
     * <p>
     * <strong><a href="../guide/ijce/JCEDifferences.html">This method
     * is not supported in JavaSoft's version of JCE.</a></strong>
     *
     * @exception NullPointerException if cipher == null
     */
    public static Cipher
    getInstance(Cipher cipher, Mode mode, PaddingScheme padding) {
        if (cipher == null) throw new NullPointerException("cipher == null");
        String cipherName = cipher.getAlgorithm();
        String modeName = (mode == null) ? "ECB" : mode.getAlgorithm();
        String paddingName =
            (padding == null) ? "NONE" : padding.getAlgorithm();
        String provider = cipher.getProvider();

        Cipher result, nested = null;
        if (mode == null)
            result = cipher;
        else {
            nested = cipher;
            result = mode;
        }
        result.setNames(cipherName, modeName, paddingName, provider);
        if (nested != null)((Mode) result).engineSetCipher(nested);
        if (padding != null) result.engineSetPaddingScheme(padding);

if (DEBUG && debuglevel >= 3) debug("Created cipher [2]: " + result);

        return result;
    }

    /**
     * Returns the state of this Cipher object. Possible states are:
     * <p>
     * <dl>
     *   <dt> UNINITIALIZED
     *     <dd> The cipher has not been initialized. 
     *   <dt> ENCRYPT
     *     <dd> The cipher has been initialized for encryption. It may be
     *          used for encryption only.
     *   <dt> DECRYPT
     *     <dd> The cipher has been initialized for decryption. It may be
     *          used for decryption only.
     * </dl>
     *
     * @return the state of this cipher object.
     *
     * @see #UNINITIALIZED
     * @see #ENCRYPT
     * @see #DECRYPT
     */
    public final int getState() { return state; }

    /**
     * Returns this algorithm's standard cipher name (<em>not</em> including
     * mode and padding).
     * <p>
     * See <a href="../guide/ijce/Algorithms.html#Cipher">
     * <cite>International JCE Standard Algorithm Names</cite></a> for a list
     * of Cipher algorithm names.
     *
     * @return the standard cipher name (such as "DES").
     */
    public final String getAlgorithm() { return cipherName; }

    /**
     * Returns this algorithm's standard mode name.
     * <p>
     * See <a href="../guide/ijce/Algorithms.html#Mode">
     * <cite>International JCE Standard Algorithm Names</cite></a> for a list
     * of Mode algorithm names.
     *
     * @return the algorithm's standard mode name (such as "CBC")
     */
    public final String getMode() {
        return (modeName == null) ? "ECB" : modeName;
    }

    /**
     * Returns this algorithm's standard padding scheme name.