别的不说，先看代码：
import java.util.*;
public class Des {
private static int[] IP = { 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 };
private static int[] IP_1 = { 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 };
private static int[] PC1 = { 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 };
private static int[] PC2 = { 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, 40, 51, 45, 33, 48, 44, 49, 39, 56, 34, 53, 46, 42, 50, 36, 29,
32 };
private static int[] E = { 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置换
private static int[] P = { 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 };
private static final int[][][] S_Box = {
{ { 14, 4, 13, 1, 2, 15, 11, 8, 3, 10, 6, 12, 5, 9, 0, 7 },
{ 0, 15, 7, 4, 14, 2, 13, 1, 10, 6, 12, 11, 9, 5, 3, 8 },
{ 4, 1, 14, 8, 13, 6, 2, 11, 15, 12, 9, 7, 3, 10, 5, 0 },
{ 15, 12, 8, 2, 4, 9, 1, 7, 5, 11, 3, 14, 10, 0, 6, 13 } },
{ { 15, 1, 8, 14, 6, 11, 3, 4, 9, 7, 2, 13, 12, 0, 5, 10 },
{ 3, 13, 4, 7, 15, 2, 8, 14, 12, 0, 1, 10, 6, 9, 11, 5 },
{ 0, 14, 7, 11, 10, 4, 13, 1, 5, 8, 12, 6, 9, 3, 2, 15 },
{ 13, 8, 10, 1, 3, 15, 4, 2, 11, 6, 7, 12, 0, 5, 14, 9 } },
{ { 10, 0, 9, 14, 6, 3, 15, 5, 1, 13, 12, 7, 11, 4, 2, 8 },
{ 13, 7, 0, 9, 3, 4, 6, 10, 2, 8, 5, 14, 12, 11, 15, 1 },
{ 13, 6, 4, 9, 8, 15, 3, 0, 11, 1, 2, 12, 5, 10, 14, 7 },
{ 1, 10, 13, 0, 6, 9, 8, 7, 4, 15, 14, 3, 11, 5, 2, 12 } },
{ { 7, 13, 14, 3, 0, 6, 9, 10, 1, 2, 8, 5, 11, 12, 4, 15 },
{ 13, 8, 11, 5, 6, 15, 0, 3, 4, 7, 2, 12, 1, 10, 14, 9 },
{ 10, 6, 9, 0, 12, 11, 7, 13, 15, 1, 3, 14, 5, 2, 8, 4 },
{ 3, 15, 0, 6, 10, 1, 13, 8, 9, 4, 5, 11, 12, 7, 2, 14 } },
{ { 2, 12, 4, 1, 7, 10, 11, 6, 8, 5, 3, 15, 13, 0, 14, 9 },
{ 14, 11, 2, 12, 4, 7, 13, 1, 5, 0, 15, 10, 3, 9, 8, 6 },
{ 4, 2, 1, 11, 10, 13, 7, 8, 15, 9, 12, 5, 6, 3, 0, 14 },
{ 11, 8, 12, 7, 1, 14, 2, 13, 6, 15, 0, 9, 10, 4, 5, 3 } },
{ { 12, 1, 10, 15, 9, 2, 6, 8, 0, 13, 3, 4, 14, 7, 5, 11 },
{ 10, 15, 4, 2, 7, 12, 9, 5, 6, 1, 13, 14, 0, 11, 3, 8 },
{ 9, 14, 15, 5, 2, 8, 12, 3, 7, 0, 4, 10, 1, 13, 11, 6 },
{ 4, 3, 2, 12, 9, 5, 15, 10, 11, 14, 1, 7, 6, 0, 8, 13 } },
{ { 4, 11, 2, 14, 15, 0, 8, 13, 3, 12, 9, 7, 5, 10, 6, 1 },
{ 13, 0, 11, 7, 4, 9, 1, 10, 14, 3, 5, 12, 2, 15, 8, 6 },
{ 1, 4, 11, 13, 12, 3, 7, 14, 10, 15, 6, 8, 0, 5, 9, 2 },
{ 6, 11, 13, 8, 1, 4, 10, 7, 9, 5, 0, 15, 14, 2, 3, 12 } },
{ { 13, 2, 8, 4, 6, 15, 11, 1, 10, 9, 3, 14, 5, 0, 12, 7 },
{ 1, 15, 13, 8, 10, 3, 7, 4, 12, 5, 6, 11, 0, 14, 9, 2 },
{ 7, 11, 4, 1, 9, 12, 14, 2, 0, 6, 10, 13, 15, 3, 5, 8 },
{ 2, 1, 14, 7, 4, 10, 8, 13, 15, 12, 9, 0, 3, 5, 6, 11 } } };
private static int[] LFT = { 1, 1,2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1 };
private static int[][] sub_key = new int[16][48];
public static void main(String[] args) {
// TODO Auto-generated method stub
// String result = Integer.toBinaryString(157);
// int r = Integer.parseInt(result);
// System.out.println(r);
// char xx=result.charAt(1);
//System.out.println(result);
// int a=Integer.valueOf(xx);
// byte hh=127;
// System.out.println(hh);
Scanner input = new Scanner(System.in);
// Input the Text and the Key;
System.out.println("请输入密钥");
String Key = input.nextLine();
System.out.println("请输入原文");
String Text = input.nextLine();
System.out.println("原文：" + Text);
System.out.println("密钥：" + Key);
getchildkey(Key);
byte[] c = deal(Text.getBytes(),1);
byte[] secret = deal(c,0);
System.out.println("密文："+ new String(c));
System.out.println("解密："+ new String(secret));
}
public static byte[] deal(byte[] text_bit,int flag) {
int text_bit_length = text_bit.length;
int r, g;
g = text_bit_length / 8;
r = 8 - (text_bit_length - g * 8);// 8不填充,r是填充的个数
byte[] p_padding;
if (r < 8) {
p_padding = new byte[text_bit_length + r];
System.arraycopy(text_bit, 0, p_padding, 0, text_bit_length);
for (int i = 0; i < r; i++) {
p_padding[text_bit_length + i] = (byte) r;
}
} else {
p_padding = text_bit;
}
g = p_padding.length / 8;
byte[] f_p = new byte[8];
byte[] result_data = new byte[p_padding.length];
for (int i = 0; i < g; i++) {
System.arraycopy(p_padding, i * 8, f_p, 0, 8);
System.arraycopy(descryUnit(f_p,flag), 0, result_data, i * 8, 8);
}
return result_data;
}
public static byte[] descryUnit(byte[] p,int flag) {
byte[] p_bit = new byte[64];
StringBuilder stringBuilder = new StringBuilder();
for (int i = 0; i < 8; i++) {
String p_b = Integer.toBinaryString(p[i]);
while (p_b.length() % 8 != 0) {
p_b = "0" + p_b;
}
stringBuilder.append(p_b);// Get 64bit data.
}
String p_str = stringBuilder.toString();
for (int i = 0; i < 64; i++) {
int p_t = Integer.valueOf(p_str.charAt(i));
if (p_t == 48) {
p_t = 0;
} else if (p_t == 49) {
p_t = 1;
} else {
System.out.println("To bit error!");
}
p_bit[i] = (byte) p_t;
}
/*for (int i = 0; i < 8; i++) {
for (int j = 0; j < 8; j++)
System.out.print(p_bit[i * 8 + j]);
System.out.println();
}*/
byte[] newp_IP = new byte[64];
for (int i = 0; i < IP.length; i++) {
newp_IP[i] = p_bit[IP[i] - 1];// ip置换
}
if(flag==0){
for (int i = 0; i < 16; i++) {
LR(newp_IP, sub_key[i]);
}}
else{
for (int i = 15; i >=0; i--) {
LR(newp_IP, sub_key[i]);
}
}
int[] c = new int[64];
for (int i = 0; i < IP_1.length; i++) {
c[i] = newp_IP[IP_1[i] - 1];
}
byte[] c_byte = new byte[8];
for (int i = 0; i < 8; i++) {
c_byte[i] = (byte) ((c[8 * i] << 7) + (c[8 * i + 1] << 6) + (c[8 * i + 2] << 5)
+ (c[8 * i + 3] << 4) + (c[8 * i + 4] << 3) + (c[8 * i + 5] << 2)
+ (c[8 * i + 6] << 1) + (c[8 * i + 7]));
}
return c_byte;
}
public static void LR(byte[] newp_IP, int[] key) {
byte[] L0 = new byte[32];
byte[] R0 = new byte[32];
byte[] L1 = new byte[32];
byte[] R1 = new byte[32];
byte[] f = new byte[32];
System.arraycopy(newp_IP, 0, L0, 0, 32);
System.arraycopy(newp_IP, 32, R0, 0, 32);
L1 = R0;
f = lrchange(key, R0);
for (int j = 0; j < 32; j++) {
R1[j] = (byte) (L0[j] ^ f[j]);
newp_IP[j] = R1[j];
newp_IP[j + 32] = L1[j];
}
}
public static byte[] lrchange(int[] key, byte[] R) {
byte[] R_E = new byte[48];
byte[] e_k = new byte[48];
byte[] s_after = new byte[32];
for (int i = 0; i < 48; i++) {
R_E[i] = R[E[i]-1];
}
for (int i = 0; i < 48; i++) {
e_k[i] = (byte) (R_E[i] ^ key[i]);
}
byte[][] S_group = new byte[8][6];
for (int i = 0; i < 8; i++) {
for (int j = 0; j < 6; j++) {
S_group[i][j] = e_k[i * 6 + j];
}
}
for (int i = 0; i < 8; i++) {
int r = (S_group[i][0] << 1) + S_group[i][5];// 横坐标
int c = (S_group[i][1] << 3) + (S_group[i][2] << 2) + (S_group[i][3] << 1) + S_group[i][4];// 纵坐标
String str = Integer.toBinaryString(S_Box[i][r][c]);
while (str.length() < 4) {
str = "0" + str;
}
for (int j = 0; j < 4; j++) {
int p = Integer.valueOf(str.charAt(j));
if (p == 48) {
p = 0;
} else if (p == 49) {
p = 1;
} else {
System.out.println("To bit error!");
}
s_after[4 * i + j] = (byte) p;
}
}
byte[] result = new byte[32];
for (int i = 0; i < P.length; i++) {
result[i] = s_after[P[i] - 1];
}
return result;
}
public static void getchildkey(String key) {
while (key.length() < 8) {
key = key + key;
}
key = key.substring(0, 8);
byte[] keys = key.getBytes();
int[] k_bit = new int[64];
// 取位值
for (int i = 0; i < 8; i++) {
String k_str = Integer.toBinaryString(keys[i]);
while(k_str.length() < 8) {
k_str = "0" + k_str;
}
for (int j = 0; j < 8; j++) {
int p = Integer.valueOf(k_str.charAt(j));
if (p == 48) {
p = 0;
} else if (p == 49) {
p = 1;
} else {
System.out.println("To bit error!");
}
k_bit[i * 8 + j] = p;
}
}
int[] k_new_bit = new int[56];
for (int i = 0; i < PC1.length; i++) {
k_new_bit[i] = k_bit[PC1[i] - 1];
}
int[] c0 = new int[28];
int[] d0 = new int[28];
System.arraycopy(k_new_bit, 0, c0, 0, 28);
System.arraycopy(k_new_bit, 28, d0, 0, 28);
for (int i = 0; i < 16; i++) {// 根据LFT表格进行循环移动
int[] c1 = new int[28];
int[] d1 = new int[28];
if (LFT[i] == 1) {
System.arraycopy(c0,1,c1,0,27);
c1[27]=c0[0];
System.arraycopy(d0,1,d1,0,27);
d1[27]=d0[0];
}else if(LFT[i]==2){
System.arraycopy(c0,2,c1,0,26);
c1[26]=c0[0];
c1[27]=c0[1];
System.arraycopy(d0,2,d1,0,26);
d1[26]=d0[0];
d1[27]=d0[1];
}else{
System.out.println("error");
}
int[] tmp=new int[56];
System.arraycopy(c1,0,tmp,0,28);
System.arraycopy(d1,0,tmp,28,28);
for (int j=0;j<PC2.length;j++){//PC2压缩置换
sub_key[i][j]= tmp[PC2[j]-1];
}
c0=c1;
d0=d1;
}
}
}
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实验原理和内容：
image.png
首先我们要将输入的数据转化为二进制编码，每64个bit分为一组，不够的结尾补0。
根据用户的输入生成一个56bit的密钥，多退少补，最后根据LFT表格进行循环移动，最后得到16个密钥。
image.png
3.64bit的明文可以分解为L和R，进行扩展运算，得到48bit的数据，再与得到的密钥相异或，再进行压缩运算，变成32bit的数据，产生雪崩效应，最后再进行置换，得到R（i+1）,重复16次。
4.拓展盒原理：
image.png
拓展E盒置换之后得到48bit的数据。
5.将得到的数据和密钥进行异或
6.进行压缩运算：64个数据分成八个部分，每组6bit.
image.png
image.png
image.png
7.进行置换,得到新的LR，重复十六次。
8.密钥生成：[图片上传失败...(image-6cc794-1605172773156)]
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参考：//https://blog.csdn.net/android_jiangjun/article/details/79654940
