3DES是继DESeasy被破解后的DES加密升级版，它属于对称加密。

可指定24位长度的密钥。在java API中也有事实上现，代码例如以下：

/**

 * 3DES 的Java SDK API 实现

 * @author dxd

 * 201406917

 */

public class DES3 {

	private static final String Algorithm = "DESede";//　定义　加密算法,可用

	//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;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();

    }

}

调用时能够：

	byte[] keydata = {

    		(byte) 0x00, (byte) 0x01, (byte) 0x02, (byte) 0x03, (byte) 0x04, (byte) 0x05, (byte) 0x06, (byte) 0x07,

    		(byte) 0x08, (byte) 0x09, (byte) 0x0a, (byte) 0x0b, (byte) 0x0c, (byte) 0x0d, (byte) 0x0e, (byte) 0x0f,

    		(byte) 0x10, (byte) 0x11, (byte) 0x12, (byte) 0x13, (byte) 0x14, (byte) 0x15, (byte) 0x16, (byte) 0x17, };

	String src = "3DES加密算法" ;

	byte[] encoded = DES3.encryptMode(keydata, src.getBytes());

	System.out.println("DES3-->Encoded = " + new String(encoded));

则能够计算出原文src加密后的密文。