DES加解密原理Java实现算法

DES(Data Encryption Standard)是对称加解密算法的一种，由IBM公司W.Tuchman和C.Meyer在上个世纪70年代开发。

该算法使用64位密钥（其中包含8位奇偶校验，实际密钥长度为56位）对以64位为单位的块数据加密，产生64位密文数据，然后使用相同的密钥进行解密。

密钥只有通信双方知晓，不对第三方公开。

DES特点
对称算法：加密和解密使用同一秘钥

分组加密算法：以64位为分组。64位明文输入，64位密文输出。

有效秘钥长度为56位秘钥通常表示为64位数，但每个第8位用作奇偶校验，可以忽略。

代替和置换DES算法是两种加密技术的组合：混乱和扩散。先替代后置换。

易于实现：DES算法只是使用了标准的算术和逻辑运算，其作用的数最多也只有64 位，因此用70年代末期的硬件技术很容易实现算法的重复特性使得它可以非常理想地用在一个专用芯片中。

可通过多重加密，提高安全等级
 

源码实现

package tes;
public class DES {
    // 置换IP表
    private int[] IP_Table = { 58, 50, 42, 34, 26, 18, 10, 2, 60, 52, 44, 36, 28, 20, 12, 4, 62, 54, 46, 38, 30, 22, 14,
            6, 64, 56, 48, 40, 32, 24, 16, 8, 57, 49, 41, 33, 25, 17, 9, 1, 59, 51, 43, 35, 27, 19, 11, 3, 61, 53, 45,
            37, 29, 21, 13, 5, 63, 55, 47, 39, 31, 23, 15, 7 };
    // 逆置换IP-1表
    private int[] IPR_Table = { 40, 8, 48, 16, 56, 24, 64, 32, 39, 7, 47, 15, 55, 23, 63, 31, 38, 6, 46, 14, 54, 22, 62,
            30, 37, 5, 45, 13, 53, 21, 61, 29, 36, 4, 44, 12, 52, 20, 60, 28, 35, 3, 43, 11, 51, 19, 59, 27, 34, 2, 42,
            10, 50, 18, 58, 26, 33, 1, 41, 9, 49, 17, 57, 25 };
    // E位选择表(扩展置换表)
    private int[] E_Table = { 32, 1, 2, 3, 4, 5, 4, 5, 6, 7, 8, 9, 8, 9, 10, 11, 12, 13, 12, 13, 14, 15, 16, 17, 16, 17,
            18, 19, 20, 21, 20, 21, 22, 23, 24, 25, 24, 25, 26, 27, 28, 29, 28, 29, 30, 31, 32, 1 };
    // P换位表(单纯换位表)
    private int[] P_Table = { 16, 7, 20, 21, 29, 12, 28, 17, 1, 15, 23, 26, 5, 18, 31, 10, 2, 8, 24, 14, 32, 27, 3, 9,
            19, 13, 30, 6, 22, 11, 4, 25 };
    // PC1选位表(密钥生成置换表1)
    private int[] PC1_Table = { 57, 49, 41, 33, 25, 17, 9, 1, 58, 50, 42, 34, 26, 18, 10, 2, 59, 51, 43, 35, 27, 19, 11,
            3, 60, 52, 44, 36, 63, 55, 47, 39, 31, 23, 15, 7, 62, 54, 46, 38, 30, 22, 14, 6, 61, 53, 45, 37, 29, 21, 13,
            5, 28, 20, 12, 4 };
    // PC2选位表(密钥生成置换表2)
    private int[] PC2_Table = { 14, 17, 11, 24, 1, 5, 3, 28, 15, 6, 21, 10, 23, 19, 12, 4, 26, 8, 16, 7, 27, 20, 13, 2,
            41, 52, 31, 37, 47, 55, 30, 4