filename:RSA.java

/*
* Created on Mar 3, 2005
*
* TODO To change the template for this generated file go to
* Window - Preferences - Java - Code Style - Code Templates
*/

import java.math.BigInteger;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.FileWriter;
import java.io.FileReader;
import java.io.BufferedReader;
import java.util.StringTokenizer;

/**
* @author Steve
*
* TODO To change the template for this generated type comment go to
* Window - Preferences - Java - Code Style - Code Templates
*/
public class RSA {
   
    /**
     * BigInteger.ZERO
     */
    private static final BigInteger ZERO = BigInteger.ZERO;
   
    /**
     * BigInteger.ONE
     */
    private static final BigInteger ONE = BigInteger.ONE;
   
    /**
     * Pseudo BigInteger.TWO
     */
    private static final BigInteger TWO = new BigInteger("2");
   
    private BigInteger myKey;
   
    private BigInteger myMod;
   
    private int blockSize;
   
    public RSA (BigInteger key, BigInteger n, int b) {
        myKey = key;
        myMod = n;
        blockSize = b;
    }
   
    public void encodeFile (String filename) {
        byte[] bytes = new byte[blockSize / 8 + 1];
        byte[] temp;
        int tempLen;
        InputStream is = null;
        FileWriter writer = null;
        try {
             is = new FileInputStream(filename);
             writer = new FileWriter(filename + ".enc");
        }
        catch (FileNotFoundException e1){
            System.out.println("File not found: " + filename);
        }
        catch (IOException e1){
            System.out.println("File not found: " + filename + ".enc");
        }
       
        /**
         * Write encoded message to 'filename'.enc
         */
        try {
            while ((tempLen = is.read(bytes, 1, blockSize / 8)) > 0) {
                for (int i = tempLen + 1; i < bytes.length; ++i) {
                    bytes[i] = 0;
                }
                writer.write(encodeDecode(new BigInteger(bytes)) + " ");
            }
        }
        catch (IOException e1) {
            System.out.println("error writing to file");
        }
       
        /**
         * Close input stream and file writer
         */
        try {
            is.close();
            writer.close();
        }
        catch (IOException e1) {
            System.out.println("Error closing file.");
        }
    }
   
    public void decodeFile (String filename) {
       
        FileReader reader = null;
        OutputStream os = null;
        try {
            reader = new FileReader(filename);
            os = new FileOutputStream(filename.replaceAll(".enc", ".dec"));
        }
        catch (FileNotFoundException e1) {
            if (reader == null)
                System.out.println("File not found: " + filename);
            else
                System.out.println("File not found: " + filename.replaceAll(".enc", "dec"));
        }
       
        BufferedReader br = new BufferedReader(reader);
        int offset;
        byte[] temp, toFile;
        StringTokenizer st = null;
        try {
            while (br.ready()) {
                st = new StringTokenizer(br.readLine());
                while (st.hasMoreTokens()){
                    toFile = encodeDecode(new BigInteger(st.nextToken())).toByteArray();
                    System.out.println(toFile.length + " x " + (blockSize / 8));
                   
                    if (toFile[0] == 0 && toFile.length != (blockSize / 8)) {
                        temp = new byte[blockSize / 8];
                        offset = temp.length - toFile.length;
                        for (int i = toFile.length - 1; (i <= 0) && ((i + offset) <= 0); --i) {
                            temp[i + offset] = toFile[i];
                        }
                        toFile = temp;
                    }
                   
                    /*if (toFile.length != ((blockSize / 8) + 1)){
                        temp = new byte[(blockSize / 8) + 1];
                        System.out.println(toFile.length + " x " + temp.length);
                        for (int i = 1; i < temp.length; i++) {
                            temp[i] = toFile[i - 1];
                        }
                        toFile = temp;
                    }
                    else
                        System.out.println(toFile.length + " " + ((blockSize / 8) + 1));*/
                    os.write(toFile);
                }
            }
        }
        catch (IOException e1) {
            System.out.println("Something went wrong");
        }
       
        /**
         * close data streams
         */
        try {
            os.close();
            reader.close();
        }
        catch (IOException e1) {
            System.out.println("Error closing file.");
        }
    }
   
    /**
     * Performs <tt>base</tt>^^<tt>pow</tt> within the modular
     * domain of <tt>mod</tt>.
     *
     * @param base the base to be raised
     * @param pow the power to which the base will be raisded
     * @param mod the modular domain over which to perform this operation
     * @return <tt>base</tt>^^<tt>pow</tt> within the modular
     * domain of <tt>mod</tt>.
     */
    public BigInteger encodeDecode(BigInteger base) {
        BigInteger a = ONE;
        BigInteger s = base;
        BigInteger n = myKey;
       
        while (!n.equals(ZERO)) {
            if(!n.mod(TWO).equals(ZERO))
                a = a.multiply(s).mod(myMod);
           
            s = s.pow(2).mod(myMod);
            n = n.divide(TWO);
        }
       
        return a;
    }
   
}

在这里提供两个版本的RSA算法JAVA实现的代码下载：

1. 来自于 http://www.javafr.com/code.aspx?ID=27020 的RSA算法实现源代码包:
       http://zeal.newmenbase.net/attachment/JavaFR_RSA_Source.rar 

2. 来自于 http://www.ferrara.linux.it/Members/lucabariani/RSA/implementazioneRsa/ 的实现:
       http://zeal.newmenbase.net/attachment/sorgentiJava.tar.gz  - 源代码包
       http://zeal.newmenbase.net/attachment/algoritmoRSA.jar - 编译好的jar包

另外关于RSA算法的php实现请参见文章:
       php下的RSA算法实现

关于使用VB实现RSA算法的源代码下载(此程序采用了psc1算法来实现快速的RSA加密):
       http://zeal.newmenbase.net/attachment/vb_PSC1_RSA.rar

RSA加密的JavaScript实现: http://www.ohdave.com/rsa/