signature.java

来自「《移动Agent技术》一书的所有章节源代码。」· Java 代码 · 共 597 行 · 第 1/2 页

    /**
     * Updates the data to be signed or verified by a byte.
     *
     * @param b the byte to use for the update.
     * 
     * @exception SignatureException if this signature object is not 
     * initialized properly.     
     */
    public final void update(byte b) throws SignatureException {
	if (state == VERIFY || state == SIGN) {
	    engineUpdate(b);
	} else {
	    throw new SignatureException("object not initialized for signature " +
					 "or verification.");
	}
    }

    /**
     * Updates the data to be signed or verified, using the specified
     * array of bytes.
     *
     * @param data the byte array to use for the update.       
     * 
     * @exception SignatureException if this signature object is not 
     * initialized properly.          
     */
    public final void update(byte[] data) throws SignatureException {
	update(data, 0, data.length);
    }

    /**
     * Updates the data to be signed or verified, using the specified
     * array of bytes, starting at the specified offset.  
     *
     * @param data the array of bytes.  
     * @param off the offset to start from in the array of bytes.  
     * @param len the number of bytes to use, starting at offset.
     *  
     * @exception SignatureException if this signature object is not 
     * initialized properly.          
     */
    public final void update(byte[] data, int off, int len) 
    throws SignatureException {
	if (state == SIGN || state == VERIFY) {
	    engineUpdate(data, off, len);
	} else {
	    throw new SignatureException("object not initialized for signature " +
					 "or verification.");
	}
    }

    /** 
     * Returns the name of the algorithm for this signature object.
     * 
     * @return the name of the algorithm for this signature object.
     */
    public final String getAlgorithm() {
	return algorithm;
    }

    /**
     * Returns a string representation of this signature object,       
     * providing information that includes the state of the object       
     * and the name of the algorithm used.       
     * 
     * @return a string representation of this signature object.
     */
    public String toString() {
	String initState = "";
	switch (state) {
	case UNINITIALIZED:
	    initState = "<not initialized>";
	    break;
	  case VERIFY:
	    initState = "<initialized for verifying>";
	    break;	      
	  case SIGN:
	    initState = "<initialized for signing>";
	    break;	      
	}
	return "Signature object: " + getAlgorithm() + initState;
    }

    /**
     * Sets the specified algorithm parameter to the specified value.
     * This method supplies a general-purpose mechanism through
     * which it is possible to set the various parameters of this object. 
     * A parameter may be any settable parameter for the algorithm, such as 
     * a parameter size, or a source of random bits for signature generation 
     * (if appropriate), or an indication of whether or not to perform
     * a specific but optional computation. A uniform algorithm-specific 
     * naming scheme for each parameter is desirable but left unspecified 
     * at this time.
     *
     * @param param the string identifier of the parameter.
     * @param value the parameter value.
     *
     * @exception InvalidParameterException if <code>param</code> is an
     * invalid parameter for this signature algorithm engine,
     * the parameter is already set
     * and cannot be set again, a security exception occurs, and so on.
     */
    public final void setParameter(String param, Object value) 
	throws InvalidParameterException {
	engineSetParameter(param, value);
    }

    /**
     * Gets the value of the specified algorithm parameter. This method 
     * supplies a general-purpose mechanism through which it is possible to 
     * get the various parameters of this object. A parameter may be any 
     * settable parameter for the algorithm, such as a parameter size, or 
     * a source of random bits for signature generation (if appropriate), 
     * or an indication of whether or not to perform a specific but optional 
     * computation. A uniform algorithm-specific naming scheme for each 
     * parameter is desirable but left unspecified at this time.
     *
     * @param param the string name of the parameter.
     *
     * @return the object that represents the parameter value, or null if
     * there is none.
     *
     * @exception InvalidParameterException if <code>param</code> is an invalid
     * parameter for this engine, or another exception occurs while
     * trying to get this parameter.
     */
    public final Object getParameter(String param) 
	throws InvalidParameterException {
	    return engineGetParameter(param);
    }

    /**
     * <b>SPI</b>: Initializes this signature object with the specified
     * public key for verification operations.
     *
     * @param publicKey the public key of the identity whose signature is
     * going to be verified.
     * 
     * @exception InvalidKeyException if the key is improperly
     * encoded, parameters are missing, and so on.  
     */
    protected abstract void engineInitVerify(PublicKey publicKey)
    throws InvalidKeyException;

    /**
     * <b>SPI</b>: Initializes this signature object with the specified
     * private key for signing operations.
     *
     * @param privateKey the private key of the identity whose signature
     * will be generated.
     *
     * @exception InvalidKeyException if the key is improperly
     * encoded, parameters are missing, and so on. 
     */
    protected abstract void engineInitSign(PrivateKey privateKey)
    throws InvalidKeyException;

   /**
     * <b>SPI</b>: Updates the data to be signed or verified
     * using the specified byte.
     *
     * @param b the byte to use for the update.
     *
     * @exception SignatureException if the engine is not initialized
     * properly.
     */
    protected abstract void engineUpdate(byte b) throws SignatureException;

    /**
     * <b>SPI</b>: Updates the data to be signed or verified, using the 
     * specified array of bytes, starting at the specified offset.
     *
     * @param data the array of bytes.  
     * @param off the offset to start from in the array of bytes.  
     * @param len the number of bytes to use, starting at offset.
     *
     * @exception SignatureException if the engine is not initialized 
     * properly.
     */
    protected abstract void engineUpdate(byte[] b, int off, int len) 
        throws SignatureException;

    /** 
     * <b>SPI</b>: Returns the signature bytes of all the data
     * updated so far. The signature returned is X.509-encoded.    
     * For more information about the X.509 encoding, see    
     * <a href = "../guide/security/cert2.html">X.509 certificates</a>.   
     *
     * @return the signature bytes of the signing operation's result.
     *
     * @exception SignatureException if the engine is not
     * initialized properly.  
     */
    protected abstract byte[] engineSign() throws SignatureException;

    /** 
     * <b>SPI</b>: Verifies the passed-in signature. The signature bytes 
     * are expected to be X.509-encoded. For more information about the 
     * X.509 encoding, see <a href = "../guide/security/cert2.html">X.509 
     * certificates</a>.   
     * 
     * @param sigBytes the signature bytes to be verified.
     *
     * @return true if the signature was verified, false if not. 
     *
     * @exception SignatureException if the engine is not initialized 
     * properly, or the passed-in signature is improperly encoded or 
     * of the wrong type, etc.  
     */
    protected abstract boolean engineVerify(byte[] sigBytes) 
	throws SignatureException;

    /**
     * <b>SPI</b>: Sets the specified algorithm parameter to the specified
     * value. This method supplies a general-purpose mechanism through
     * which it is possible to set the various parameters of this object. 
     * A parameter may be any settable parameter for the algorithm, such as 
     * a parameter size, or a source of random bits for signature generation 
     * (if appropriate), or an indication of whether or not to perform
     * a specific but optional computation. A uniform algorithm-specific 
     * naming scheme for each parameter is desirable but left unspecified 
     * at this time.
     *
     * @param param the string identifier of the parameter.
     *
     * @param value the parameter value.
     *
     * @exception InvalidParameterException if <code>param</code> is an
     * invalid parameter for this signature algorithm engine,
     * the parameter is already set
     * and cannot be set again, a security exception occurs, and so on. 
     */
    protected abstract void engineSetParameter(String param, Object value) 
	throws InvalidParameterException;

    /**
     * <b>SPI</b>: Gets the value of the specified algorithm parameter. 
     * This method supplies a general-purpose mechanism through which it 
     * is possible to get the various parameters of this object. A parameter
     * may be any settable parameter for the algorithm, such as a parameter 
     * size, or  a source of random bits for signature generation (if 
     * appropriate), or an indication of whether or not to perform a 
     * specific but optional computation. A uniform algorithm-specific 
     * naming scheme for each parameter is desirable but left unspecified 
     * at this time.
     *
     * @param param the string name of the parameter.
     *
     * @return the object that represents the parameter value, or null if
     * there is none.
     *
     * @exception InvalidParameterException if <code>param</code> is an 
     * invalid parameter for this engine, or another exception occurs while
     * trying to get this parameter.
     */
    protected abstract Object engineGetParameter(String param)
	throws InvalidParameterException;

    /**
     * Returns a clone if the implementation is cloneable.
     * 
     * @return a clone if the implementation is cloneable.
     *
     * @exception CloneNotSupportedException if this is called
     * on an implementation that does not support <code>Cloneable</code>.
     */
    public Object clone() throws CloneNotSupportedException {
	if (this instanceof Cloneable) {
	    return super.clone();
	} else {
	    throw new CloneNotSupportedException();
	}
    }

    // private debugging method.
    private static void debug(String statement) {
	if (debug) {
	    System.err.println(statement);
	}
    }

    // private debugging method.
    private static void debug(Exception e) {
	if (debug) {
	    e.printStackTrace();
	}
    }

}