cipheroutputstream.java

JAVA的加密源程序

/*
Christoforos Pirillos @ Villanova University - May 1999
based on code from the book "Java Network Programming" by Hughes
*/

package encryption;
import java.io.*;

/**A filtered OutputStream that attaches to an existing OutputStream and
encrypts all data written to it. The Cipher that is used to perform the
encryption is specified in the constructor*/

public class CipherOutputStream extends FilterOutputStream {

protected ByteArrayOutputStream byteO;
protected OutputStream o;
protected Cipher c;

/**In the constructor we accept an OutputStream o over which we will send
encrypted data and a Cipher c with which we will perform the encryption.*/

public CipherOutputStream (OutputStream o, Cipher c) {
	super (new ByteArrayOutputStream ());
	byteO = (ByteArrayOutputStream) out;
	this.o = o;
	this.c = c;
}

public void flush () throws IOException {
	writeEncrypted();
	o.flush();
}

public void close () throws IOException {
	flush();
	o.close();
}

/**Encrypts and sends the data that we have buffered*/

protected void writeEncrypted () throws IOException {
	if (byteO.size() > 0) {
		byte[] b = byteO.toByteArray();
		byteO.reset();
		
		byte[] plain = new byte[b.length+4];
		Crypt.intToBytes (plain.length, plain, 0);
		System.arraycopy (b, 0, plain, 4, b.length);

		byte[] cipher = c.encipher (plain);
		o.write (cipher);
	}
}

} /* end of class CipherOutputStream */