夢幻之旅

在java中調用sun公司提供的3DES加密解密算法時，需要使用到$JAVA_HOME/jre/lib/目錄下如下的4個jar包：
jce.jar
security/US_export_policy.jar
security/local_policy.jar
ext/sunjce_provider.jar

Java運行時會自動加載這些包，因此對于帶main函數的應用程序不需要設置到CLASSPATH環境變量中。對于WEB應用，不需要把這些包加到WEB-INF/lib目錄下。

以下是java中調用sun公司提供的3DES加密解密算法的樣本代碼：

/*
字符串 DESede(3DES) 加密
*/
import java.security.*;
import javax.crypto.*;
import javax.crypto.spec.SecretKeySpec;

public class ThreeDes {

    private static final String Algorithm = "DESede"; //定義 加密算法,可用 DES,DESede,Blowfish
    
    //keybyte為加密密鑰，長度為24字節
    //src為被加密的數據緩沖區（源）
    public static byte[] encryptMode(byte[] keybyte, byte[] src) {
       try {
            //生成密鑰
            SecretKey deskey = new SecretKeySpec(keybyte, Algorithm);

            //加密
            Cipher c1 = Cipher.getInstance(Algorithm);
            c1.init(Cipher.ENCRYPT_MODE, deskey);
            return c1.doFinal(src);
        } catch (java.security.NoSuchAlgorithmException e1) {
            e1.printStackTrace();
        } catch (javax.crypto.NoSuchPaddingException e2) {
            e2.printStackTrace();
        } catch (java.lang.Exception e3) {
            e3.printStackTrace();
        }
        return null;
    }

    //keybyte為加密密鑰，長度為24字節
    //src為加密后的緩沖區
    public static byte[] decryptMode(byte[] keybyte, byte[] src) {      
	try {
            //生成密鑰
            SecretKey deskey = new SecretKeySpec(keybyte, Algorithm);

            //解密
            Cipher c1 = Cipher.getInstance(Algorithm);
            c1.init(Cipher.DECRYPT_MODE, deskey);
            return c1.doFinal(src);
        } catch (java.security.NoSuchAlgorithmException e1) {
            e1.printStackTrace();
        } catch (javax.crypto.NoSuchPaddingException e2) {
            e2.printStackTrace();
        } catch (java.lang.Exception e3) {
            e3.printStackTrace();
        }
        return null;
    }

    //轉換成十六進制字符串
    public static String byte2hex(byte[] b) {
        String hs="";
        String stmp="";

        for (int n=0;n<b.length;n++) {
            stmp=(java.lang.Integer.toHexString(b[n] & 0XFF));
            if (stmp.length()==1) hs=hs+"0"+stmp;
            else hs=hs+stmp;
            if (n<b.length-1)  hs=hs+":";
        }
        return hs.toUpperCase();
    }
    
    public static void main(String[] args)
    {
        //添加新安全算法,如果用JCE就要把它添加進去
        Security.addProvider(new com.sun.crypto.provider.SunJCE());

        final byte[] keyBytes = {0x11, 0x22, 0x4F, 0x58, (byte)0x88, 0x10, 0x40, 0x38
                               , 0x28, 0x25, 0x79, 0x51, (byte)0xCB, (byte)0xDD, 0x55, 0x66
                               , 0x77, 0x29, 0x74, (byte)0x98, 0x30, 0x40, 0x36, (byte)0xE2};	//24字節的密鑰
        String szSrc = "This is a 3DES test. 測試";
        
        System.out.println("加密前的字符串:" + szSrc);
        
        byte[] encoded = encryptMode(keyBytes, szSrc.getBytes());        
        System.out.println("加密后的字符串:" + new String(encoded));
        
        byte[] srcBytes = decryptMode(keyBytes, encoded);
        System.out.println("解密后的字符串:" + (new String(srcBytes)));
    }
}