jce.jar
security/US_export_policy.jar
security/local_policy.jar
ext/sunjce_provider.jar
Java运行时会自动加载这些包，因此对于带main函数的应用程序不需要设置到CLASSPATH环境变量中。对于WEB应用，不需要把这些包加到WEB-INF/lib目录下。
以下是java中调用sun公司提供的3DES加密解密算法的样本代码：
代码如下：

/*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"; //定义 加密算法,可用 DES,DESede,Blowfish

//keybyte为加密密钥，长度为24字节
//src为被加密的数据缓冲区（源）
public static byte[] encryptMode(byte[] keybyte, byte[] src) {
try {
//生成密钥
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为加密密钥，长度为24字节
//src为加密后的缓冲区
public static byte[] decryptMode(byte[] keybyte, byte[] src) {
try {
//生成密钥
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;
}

//转换成十六进制字符串
public static String byte2hex(byte[] b) {
String hs="";
String stmp="";
for (int n=0;nb.length;n++) {
stmp=(java.lang.Integer.toHexString(b[n] & 0XFF));
if (stmp.length()==1) hs=hs+"0"+stmp;
else hs=hs+stmp;
if (nb.length-1) hs=hs+":";
}
return hs.toUpperCase();
}
public static void main(String[] args){

//添加新安全算法,如果用JCE就要把它添加进去
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字节的密钥

String szSrc = "This is a 3DES test. 测试";
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)));
}
}