HELP：java中如何用私钥进行加密，用公钥解密？？？急急急急。。。。

Question

/**
 * FileName:   Encryptstr.java
 * Description: 字符串加密：通过指定相同长度的key字符串，将源字符串和Key字符串的Ascii码进行异或，并进行简单操作，获得加密后的数字字符串
 * Copyright: Copyright (c) 2003
 * @Author: Totodo
 * @Email: [email protected]
 * @Version: 1.0
 */
public class Encryptstr {
static String sWrong;
static String sSkey="207806514039";public Encryptstr() {
sWrong="";
}public static String encryptkey(String sKey,int iLength) {
//获取指定长度的key
String sKeystr=sKey;
int kLength;
kLength=sKey.length();
if (iLength<=kLength)
sKeystr=sKey.substring(0,iLength); //截取和加密字符串长度相等的key
else {
//重复key使长度相等
while (kLength<iLength) {
if (kLength+sKey.length()>=iLength) {
sKeystr=sKeystr+sKey.substring(0,iLength-kLength);
}
else {
sKeystr=sKeystr+sKey;
}
kLength=sKeystr.length();
}
}
return sKeystr;

}public  String encrypt(String sKey,String sSource) {
//加密字符串
String sTarget="";
String sKeystr;//和加密字符串长度相等的key
int sLength;//加密字符串长度
char cS,cK,cT;
int iS,iK,iT;
int i;

if (sSource=="") {
sWrong="字符串为空！";
return sTarget;
}
if (sKey=="") {
sWrong="请指定密钥！";
return sTarget;
}

sLength=sSource.length();
sKeystr=encryptkey(sKey,sLength);

for (i=0;i<sLength;i++) {
cS=sSource.charAt(i);
cK=sKeystr.charAt(i);
iS=(int)cS;
iK=(int)cK;
iT=iS^iK;
// System.out.print(iS);
// System.out.print(" ");
// System.out.print(iK);
// System.out.print(" ");
// System.out.print(iT);
// System.out.print(" ");
// System.out.println(iT+29);
iT=iT+29;
iT=1000+iT/10%10*100+iT/100*10+iT%10;//十位、百位、个位
sTarget=sTarget+Integer.toString(iT).substring(1);
}

return sTarget;
}public String encrypt(String sSource) {
return encrypt(sSkey,sSource);
}public static String decode(String sKey,String sTarget) {
//解密

String sSource="";
String sKeystr;//和解密字符串长度相等的key
int sLength; //解密字符串长度
char cS,cK;
String cT;
int iS,iK,iT;
int i; if (sTarget=="") {
sWrong="字符串为空！";
return sSource;
}
if (sKey=="") {
sWrong="请指定密钥！";
return sSource;
}

sLength=sTarget.length()/3;
sKeystr=encryptkey(sKey,sLength);

for (i=0;i<sLength;i++) {
cT=sTarget.substring(i*3,(i+1)*3);
cK=sKeystr.charAt(i);
iT=Integer.parseInt(cT);
iT=iT/10%10*100+iT/100*10+iT%10;
iK=(int)cK;
iS=(iT-29)^iK;
// System.out.print(iT);
// System.out.print(" ");
// System.out.print(iT-29);
// System.out.print(" ");
// System.out.print(iK);
// System.out.print(" ");
// System.out.println(iS);
cS=(char)iS;
sSource=sSource+cS;
} return sSource;
}public static String decode(String sTarget) {
return decode(sSkey,sTarget);
}public static void main(String[] args) throws Exception{ 
String str;
Encryptstr en_str = new Encryptstr();
str=en_str.encrypt("abcde");
System.out.println("abcde加密后的字符传:"+str);
System.out.println("adcde解迷后的字符船:"+decode("207806514039",str));
}
}

Answer 1

标准DES算法
/**
 * <p>Title: </p>
 * <p>Description: </p>
 * <p>Copyright: Copyright (c) 2004</p>
 * <p>Company: </p>
 * @author not attributable
 * @version 1.0
 */
import java.io.*;import javax.crypto.*;
import java.security.*;public class DESCryptoTest {
  public static void main(String[] args) {
//    Security.addProvider(new com.sun.crypto.provider.SunJCE());
    Security.addProvider(new org.bouncycastle.jce.provider.BouncyCastleProvider());
    KeyGenerator kg = null;
    try {
      //指定算法,这里为DES;如果想用Blowfish算法,则用 getInstance("Blowfish")
      //BouncyCastle基本上支持所有通用标准算法
      kg = KeyGenerator.getInstance("DES", "BC");      //指定密钥长度,长度越高,加密强度越大
      kg.init(56);      //产生密钥
      Key key = kg.generateKey();
      System.out.println("Key format: " + key.getFormat());
      System.out.println("Key algorithm: " + key.getAlgorithm());      //加密要用Cipher来实现
      Cipher cipher = Cipher.getInstance("DES");
      System.out.println("Cipher provider: " + cipher.getProvider());
      System.out.println("Cipher algorithm: " + cipher.getAlgorithm());      byte[] data = "Hello World!".getBytes();
      System.out.println("Original data : [" + data.length + "]" +
                         new String(data));      //设置加密模式
      cipher.init(Cipher.ENCRYPT_MODE, key);
      byte[] result = cipher.doFinal(data);
      System.out.println("Encrypted data: [" + result.length + "]" +
                         new String(result));      //设置解密模式
      cipher.init(Cipher.DECRYPT_MODE, key);
      byte[] original = cipher.doFinal(result);
      System.out.println("Decrypted data: [" + original.length + "]" +
                         new String(original));      String filename = "加密前.txt";
      //读入并加密文件
      try {
        //输入流
        cipher.init(Cipher.ENCRYPT_MODE, key);
        BufferedInputStream in = new BufferedInputStream(new FileInputStream(filename));
        //输出流
        CipherOutputStream out = new CipherOutputStream(new BufferedOutputStream(new FileOutputStream("加密后.txt")), cipher);
        int i;
        do {
          i = in.read();
          if (i != -1)
            out.write(i);
        }
        while (i != -1);        in.close();
        out.close();
        System.out.println("加密文件完成！");
      }
      catch (Exception ey5) {
        System.out.println("Error when encrypt the file");
        System.exit(0);
      }      try {
        cipher.init(Cipher.DECRYPT_MODE, key);
        //输出流
        BufferedOutputStream out = new BufferedOutputStream(new FileOutputStream("解密后.txt"));
        //输入流
        CipherInputStream in = new CipherInputStream(new BufferedInputStream(
            new FileInputStream("加密后.txt")), cipher);        int i;
        do {
          i = in.read();
          if (i != -1)
            out.write(i);
        }
        while (i != -1);        in.close();
        out.close();
        System.out.println("解密文件完成！");
      }
      catch (Exception ey5) {
        System.out.println("Error when encrypt the file");
        System.exit(0);
      }
    }
    catch (Exception e) {
      e.printStackTrace();
    }
  }
}