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();
    }
}

	byte[] keydata = http://www.mamicode.com/{ "3DES加密算法" ;
	byte[] encoded = DES3.encryptMode(keydata, src.getBytes());
	System.out.println("DES3-->Encoded = " + new String(encoded));