AES算法（附带代码实现）
1.AES（高级加密标准）算法是目前全球使用最广泛的对称加密算法，全称为高级加密标准（Advanced Encryption Standard），是美国联邦政府采用的一种区块加密标准。此标准用来替代原先的DES，已经被广泛使用在全球范围内。2.AES是一种对称加密算法，也就是说加密和解密使用的是同一套密钥。AES支持128、192和256位密钥长度，且支持的数据块长度为128位。
一、简要介绍
1.AES（高级加密标准）算法是目前全球使用最广泛的对称加密算法，全称为高级加密标准（Advanced Encryption Standard），是美国联邦政府采用的一种区块加密标准。此标准用来替代原先的DES，已经被广泛使用在全球范围内。
2.AES是一种对称加密算法，也就是说加密和解密使用的是同一套密钥。AES支持128、192和256位密钥长度，且支持的数据块长度为128位。
3.AES的工作过程包括：字节替代（SubBytes）、行移位（ShiftRows）、列混淆（MixColumns）和轮密钥加（AddRoundKey）。这些步骤共同构成了AES的一个加密轮次，实际的加密过程会进行多个这样的轮次。
4.AES算法的安全性很高，运行效率也很高，因此在很多场景下都有应用，包括无线通信、网络通信、数据存储等等。
AES的困难点包括：
1. S-盒（Substitution box）设计：S-盒是AES中最复杂的部分，需要对其进行适当的设计以保证加密的安全性。S-盒涉及到有限域GF(2^8)上的逆元运算和仿射变换，这部分对于初学者来说比较困难。
2. 位操作：AES使用了许多位操作，包括位移、异或、字节替换等，这些都需要对计算机二进制运算有深入理解。
3. 迭代次数：AES的迭代次数取决于密钥的长度，有10轮（128位密钥）、12轮（192位密钥）和14轮（256位密钥）三种情况。每轮的运算都包括SubBytes、ShiftRows、MixColumns和AddRoundKey四个步骤，需要对这些步骤有清晰的理解和实现。
二、AES的重要部分：
1. 密钥扩展：根据原始密钥生成一系列轮密钥，这些轮密钥用于每轮的加密操作。
2. SubBytes步骤：使用S-盒进行字节替换，增加了加密的混淆性。
3. ShiftRows步骤：通过行移位操作，增加了数据的扩散性。
4. MixColumns步骤：进一步增加了数据的扩散性。
5. AddRoundKey步骤：将轮密钥和状态矩阵进行异或操作，增加了加密的混淆性。
以上就是我的解答，希望对你有所帮助。
三、代码实现
#include <stdio.h>
#pragma warning(disable:4996)
//定义轮常量表
static const unsigned char Rcon[10] = {
0x01,0x02,0x04,0x08,0x10,0x20,0x40,0x80,0x1b,0x36 };
static unsigned char x2time(unsigned char x)
{
if (x & 0x80)
{
return (((x << 1) ^ 0x1B) & 0xFF);
}
return x << 1;
}
static unsigned char x3time(unsigned char x)
{
return (x2time(x) ^ x);
}
static unsigned char x4time(unsigned char x)
{
return (x2time(x2time(x)));
}
static unsigned char x8time(unsigned char x)
{
return (x2time(x2time(x2time(x))));
}
static unsigned char x9time(unsigned char x)
{
return (x8time(x) ^ x);
}
static unsigned char xBtime(unsigned char x)
{
return (x8time(x) ^ x2time(x) ^ x);
}
//定义有限域*D乘法
static unsigned char xDtime(unsigned char x)
{
return (x8time(x) ^ x4time(x) ^ x);
}
//定义有限域*E乘法
static unsigned char xEtime(unsigned char x)
{
return (x8time(x) ^ x4time(x) ^ x2time(x));
}
//s盒矩阵 Substitution Table
static const unsigned char sbox[256] = {
0x63,0x7c,0x77,0x7b,0xf2,0x6b,0x6f,0xc5,
0x30,0x01,0x67,0x2b,0xfe,0xd7,0xab,0x76,
0xca,0x82,0xc9,0x7d,0xfa,0x59,0x47,0xf0,
0xad,0xd4,0xa2,0xaf,0x9c,0xa4,0x72,0xc0,
0xb7,0xfd,0x93,0x26,0x36,0x3f,0xf7,0xcc,
0x34,0xa5,0xe5,0xf1,0x71,0xd8,0x31,0x15,
0x04,0xc7,0x23,0xc3,0x18,0x96,0x05,0x9a,
0x07,0x12,0x80,0xe2,0xeb,0x27,0xb2,0x75,
0x09,0x83,0x2c,0x1a,0x1b,0x6e,0x5a,0xa0,
0x52,0x3b,0xd6,0xb3,0x29,0xe3,0x2f,0x84,
0x53,0xd1,0x00,0xed,0x20,0xfc,0xb1,0x5b,
0x6a,0xcb,0xbe,0x39,0x4a,0x4c,0x58,0xcf,
0xd0,0xef,0xaa,0xfb,0x43,0x4d,0x33,0x85,
0x45,0xf9,0x02,0x7f,0x50,0x3c,0x9f,0xa8,
0x51,0xa3,0x40,0x8f,0x92,0x9d,0x38,0xf5,
0xbc,0xb6,0xda,0x21,0x10,0xff,0xf3,0xd2,
0xcd,0x0c,0x13,0xec,0x5f,0x97,0x44,0x17,
0xc4,0xa7,0x7e,0x3d,0x64,0x5d,0x19,0x73,
0x60,0x81,0x4f,0xdc,0x22,0x2a,0x90,0x88,
0x46,0xee,0xb8,0x14,0xde,0x5e,0x0b,0xdb,
0xe0,0x32,0x3a,0x0a,0x49,0x06,0x24,0x5c,
0xc2,0xd3,0xac,0x62,0x91,0x95,0xe4,0x79,
0xe7,0xc8,0x37,0x6d,0x8d,0xd5,0x4e,0xa9,
0x6c,0x56,0xf4,0xea,0x65,0x7a,0xae,0x08,
0xba,0x78,0x25,0x2e,0x1c,0xa6,0xb4,0xc6,
0xe8,0xdd,0x74,0x1f,0x4b,0xbd,0x8b,0x8a,
0x70,0x3e,0xb5,0x66,0x48,0x03,0xf6,0x0e,
0x61,0x35,0x57,0xb9,0x86,0xc1,0x1d,0x9e,
0xe1,0xf8,0x98,0x11,0x69,0xd9,0x8e,0x94,
0x9b,0x1e,0x87,0xe9,0xce,0x55,0x28,0xdf,
0x8c,0xa1,0x89,0x0d,0xbf,0xe6,0x42,0x68,
0x41,0x99,0x2d,0x0f,0xb0,0x54,0xbb,0x16,
};
//逆向S盒矩阵
static const unsigned char contrary_sbox[256] = {
0x52,0x09,0x6a,0xd5,0x30,0x36,0xa5,0x38,
0xbf,0x40,0xa3,0x9e,0x81,0xf3,0xd7,0xfb,
0x7c,0xe3,0x39,0x82,0x9b,0x2f,0xff,0x87,
0x34,0x8e,0x43,0x44,0xc4,0xde,0xe9,0xcb,
0x54,0x7b,0x94,0x32,0xa6,0xc2,0x23,0x3d,
0xee,0x4c,0x95,0x0b,0x42,0xfa,0xc3,0x4e,
0x08,0x2e,0xa1,0x66,0x28,0xd9,0x24,0xb2,
0x76,0x5b,0xa2,0x49,0x6d,0x8b,0xd1,0x25,
0x72,0xf8,0xf6,0x64,0x86,0x68,0x98,0x16,
0xd4,0xa4,0x5c,0xcc,0x5d,0x65,0xb6,0x92,
0x6c,0x70,0x48,0x50,0xfd,0xed,0xb9,0xda,
0x5e,0x15,0x46,0x57,0xa7,0x8d,0x9d,0x84,
0x90,0xd8,0xab,0x00,0x8c,0xbc,0xd3,0x0a,
0xf7,0xe4,0x58,0x05,0xb8,0xb3,0x45,0x06,
0xd0,0x2c,0x1e,0x8f,0xca,0x3f,0x0f,0x02,
0xc1,0xaf,0xbd,0x03,0x01,0x13,0x8a,0x6b,
0x3a,0x91,0x11,0x41,0x4f,0x67,0xdc,0xea,
0x97,0xf2,0xcf,0xce,0xf0,0xb4,0xe6,0x73,
0x96,0xac,0x74,0x22,0xe7,0xad,0x35,0x85,
0xe2,0xf9,0x37,0xe8,0x1c,0x75,0xdf,0x6e,
0x47,0xf1,0x1a,0x71,0x1d,0x29,0xc5,0x89,
0x6f,0xb7,0x62,0x0e,0xaa,0x18,0xbe,0x1b,
0xfc,0x56,0x3e,0x4b,0xc6,0xd2,0x79,0x20,
0x9a,0xdb,0xc0,0xfe,0x78,0xcd,0x5a,0xf4,
0x1f,0xdd,0xa8,0x33,0x88,0x07,0xc7,0x31,
0xb1,0x12,0x10,0x59,0x27,0x80,0xec,0x5f,
0x60,0x51,0x7f,0xa9,0x19,0xb5,0x4a,0x0d,
0x2d,0xe5,0x7a,0x9f,0x93,0xc9,0x9c,0xef,
0xa0,0xe0,0x3b,0x4d,0xae,0x2a,0xf5,0xb0,
0xc8,0xeb,0xbb,0x3c,0x83,0x53,0x99,0x61,
0x17,0x2b,0x04,0x7e,0xba,0x77,0xd6,0x26,
0xe1,0x69,0x14,0x63,0x55,0x21,0x0c,0x7d,
};
//定义列混合操作
static void MixColumns(unsigned char* col)
{
unsigned char tmp[4], xt[4];
int i;
for (i = 0; i < 4; i++, col += 4)
{ //col代表一列的基地址，col+4:下一列的基地址
//xt[n]代表*2 xt[n]^col[n]代表*3 col[n]代表*1
tmp[0] = x2time(col[0]) ^ x3time(col[1]) ^ col[2] ^ col[3]; //2 3 1 1
tmp[1] = col[0] ^ x2time(col[1]) ^ x3time(col[2]) ^ col[3]; //1 2 3 1
tmp[2] = col[0] ^ col[1] ^ x2time(col[2]) ^ x3time(col[3]); //1 1 2 3
tmp[3] = x3time(col[0]) ^ col[1] ^ col[2] ^ x2time(col[3]); //3 1 1 2
//修改后的值 直接在原矩阵上修改
col[0] = tmp[0];
col[1] = tmp[1];
col[2] = tmp[2];
col[3] = tmp[3];
}
}
//定义逆向列混淆
static void Contrary_MixColumns(unsigned char* col)
{
unsigned char tmp[4];
unsigned char xt2[4];//colx2
unsigned char xt4[4];//colx4
unsigned char xt8[4];//colx8
int x;
for (x = 0; x < 4; x++, col += 4)
{
tmp[0] = xEtime(col[0]) ^ xBtime(col[1]) ^ xDtime(col[2]) ^ x9time(col[3]);
tmp[1] = x9time(col[0]) ^ xEtime(col[1]) ^ xBtime(col[2]) ^ xDtime(col[3]);
tmp[2] = xDtime(col[0]) ^ x9time(col[1]) ^ xEtime(col[2]) ^ xBtime(col[3]);
tmp[3] = xBtime(col[0]) ^ xDtime(col[1]) ^ x9time(col[2]) ^ xEtime(col[3]);
col[0] = tmp[0];
col[1] = tmp[1];
col[2] = tmp[2];
col[3] = tmp[3];
}
}
//定义行移位操作：行左循环移位
static void ShiftRows(unsigned char* col)
{//正向行移位
unsigned char t;
//左移1位
t = col[1]; col[1] = col[5]; col[5] = col[9]; col[9] = col[13]; col[13] = t;
//左移2位，交换2次数字来实现
t = col[2]; col[2] = col[10]; col[10] = t;
t = col[6]; col[6] = col[14]; col[14] = t;
//左移3位，相当于右移1次
t = col[15]; col[15] = col[11]; col[11] = col[7]; col[7] = col[3]; col[3] = t;
//第4行不移位
}
//逆向行移位
static void Contrary_ShiftRows(unsigned char* col)
{
unsigned char t;
t = col[13]; col[13] = col[9]; col[9] = col[5]; col[5] = col[1]; col[1] = t;
t = col[2]; col[2] = col[10]; col[10] = t;
t = col[6]; col[6] = col[14]; col[14] = t;
t = col[3]; col[3] = col[7]; col[7] = col[11]; col[11] = col[15]; col[15] = t;
//同理，第4行不移位
}
//定义s盒字节代换替换操作
static void SubBytes(unsigned char* col)
{//字节代换
int x;
for (x = 0; x < 16; x++)
{
col[x] = sbox[col[x]];
}
}
//逆向字节代换
static void Contrary_SubBytes(unsigned char* col)
{
int x;
for (x = 0; x < 16; x++)
{
col[x] = contrary_sbox[col[x]];
}
}
//密钥编排，16字节--->44列32bit密钥生成--> 11组16字节:分别用于11轮 轮密钥加运算
void ScheduleKey(unsigned char* inkey, unsigned char* outkey, int Nk, int Nr)
{
//inkey:初始16字节密钥key
//outkey：11组*16字节扩展密钥expansionkey
//Nk：4列
//Nr：10轮round
unsigned char temp[4], t;
int x, i;
/*copy the key*/
//第0组：[0-3]直接拷贝
for (i = 0; i < (4 * Nk); i++)
{
outkey[i] = inkey[i];
}
//第1-10组：[4-43]
i = Nk;
while (i < (4 * (Nr + 1))) //i=4~43 WORD 32bit的首字节地址，每一个4字节
{//1次循环生成1个字节扩展密钥，4次循环生成一个WORD
//temp：4字节数组：代表一个WORD密钥
//i不是4的倍数的时候
//每个temp = 每个outkey32bit = 4字节
for (x = 0; x < 4; x++)
temp[x] = outkey[(4 * (i - 1)) + x]; //i：32bit的首字节地址
//i是4的倍数的时候
if (i % Nk == 0)
{
/*字循环：循环左移1字节 RotWord()*/
t = temp[0]; temp[0] = temp[1]; temp[1] = temp[2]; temp[2] = temp[3]; temp[3] = t;
/*字节代换：SubWord()*/
for (x = 0; x < 4; x++)
{
temp[x] = sbox[temp[x]];
}
/*轮常量异或：Rcon[j]*/
temp[0] ^= Rcon[(i / Nk) - 1];
}
for (x = 0; x < 4; x++)
{
outkey[(4 * i) + x] = outkey[(4 * (i - Nk)) + x] ^ temp[x];
}
++i;
}
}
//定义轮密钥加操作
static void AddRoundKey(unsigned char* col, unsigned char* expansionkey, int round)//密匙加
{
//扩展密钥：44*32bit =11*4* 4*8 = 16字节*11轮，每轮用16字节密钥
//第0轮，只进行一次轮密钥加
//第1-10轮，轮密钥加
int x;
for (x = 0; x < 16; x++)
{ //每1轮操作：4*32bit密钥 = 16个字节密钥
col[x] ^= expansionkey[(round << 4) + x];
}
}
//AES加密函数
void AesEncrypt(unsigned char* blk, unsigned char* expansionkey, int Nr)
{//加密一个区块
//输入blk原文，直接在上面修改，输出blk密文
//输入skey：
//输入Nr = 10轮
int round;
//第1轮之前：轮密钥加
AddRoundKey(blk, expansionkey, 0);
//第1-9轮：4类操作：字节代换、行移位、列混合、轮密钥加
for (round = 1; round <= (Nr - 1); round++)
{
SubBytes(blk); //输入16字节数组，直接在原数组上修改
ShiftRows(blk); //输入16字节数组，直接在原数组上修改
MixColumns(blk); //输入16字节数组，直接在原数组上修改
AddRoundKey(blk, expansionkey, round);
}
//第10轮：不进行列混合
SubBytes(blk);
ShiftRows(blk);
AddRoundKey(blk, expansionkey, Nr);
}
//AES 解密函数
void Contrary_AesEncrypt(unsigned char* blk, unsigned char* expansionkey, int Nr)
{
int x;
AddRoundKey(blk, expansionkey, Nr);
Contrary_ShiftRows(blk);
Contrary_SubBytes(blk);
for (x = (Nr - 1); x >= 1; x--)
{
AddRoundKey(blk, expansionkey, x);
Contrary_MixColumns(blk);
Contrary_ShiftRows(blk);
Contrary_SubBytes(blk);
}
AddRoundKey(blk, expansionkey, 0);
}
int main(void) {
unsigned char pt[17], key[17];
//定义原文pt
//定义密钥key
unsigned char expansionkey[15 * 16];
int i;
int j;
printf("输入明文：\n");
scanf("%s", pt);
printf("输入密钥：\n");
scanf("%s", key);
//加密过程
ScheduleKey(key, expansionkey, 4, 10);//密钥扩展生成
AesEncrypt(pt, expansionkey, 10);//调用AES 加密
printf("密文是: ");
//输出密文
for (i = 0; i < 16; i++)
{
printf("%02x ", pt[i]);
}
printf("\n");
printf("\n");
//解密过程
Contrary_AesEncrypt(pt, expansionkey, 10);//调用AES 解密
printf("明文是: ");
//输出明文
for (i = 0; i < 16; i++)
{
printf("%c ", pt[i]);
}
printf("\n");
printf("\n");
while (1);
return 0;
}
四、总结
总结来说，AES是一种广泛使用的对称加密算法，其安全性和效率高，但实现起来相对复杂。其主要挑战在于理解和实现S-盒设计、位操作和不同轮次的迭代运算。AES的核心部分包括密钥扩展、SubBytes、ShiftRows、MixColumns和AddRoundKey五个步骤，这些步骤通过混淆和扩散数据来保证加密的安全性。对于初学者来说，需要对计算机二进制运算、有限域GF(2^8)上的逆元运算和仿射变换有深入理解，才能有效地实现AES算法。
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