AES算法

时间 2019-11-19

原文原文链接

AES加密算法是密码学中的高级加密标准（Advanced Encryption Standard，AES），又称Rijndael加密法，是美国联邦政府采用的一种区块加密标准。这个标准用来替代原先的DES，高级加密标准由美国国家标准与技术研究院（NIST）于2001年11月26日发布于FIPS PUB 197，并在2002年5月26日成为有效的标准。c++

优势： 1.AES在软件及硬件上都能快速地加解密，相对来讲较易于实做，且只须要不多的存储器。 2. 有很好的抵抗差分密码分析及线性密码分析的能力。算法

对称密码体制的发展趋势将以分组密码为重点。分组密码算法一般由密钥扩展算法和加密（解密）算法两部分组成。密钥扩展算法将b字节用户主密钥扩展成r个子密钥。加密算法由一个密码学上的弱函数f与r个子密钥迭代r次组成。混乱和密钥扩散是分组密码算法设计的基本原则。抵御已知明文的差分和线性攻击，可变长密钥和分组是该体制的设计要点。函数

AES算法基于排列和置换运算。排列是对数据从新进行安排，置换是将一个数据单元替换为另外一个。AES 使用几种不一样的方法来执行排列和置换运算。 AES是一个迭代的、对称密钥分组的密码，密钥长度支持为12八、19二、256，用 128 位（16字节）分组加密和解密数据。算法应易于各类硬件和软件实现。 AES加密数据块大小最大是256bit，可是密钥大小在理论上没有上限。对称密钥密码使用相同的密钥加密和解密数据。经过分组密码返回的加密数据的位数与输入数据相同。迭代加密使用一个循环结构，在该循环中重复置换和替换输入数据。测试

原理：1.圈变化：AES每个圈变换由如下三个层组成:编码

a. 非线性层——进行Subbyte变换：做用在状态中每一个字节上的一种非线性字节转换,能够经过计算出来的S盒进行映射。将指针指向S盒的首地址，将要查找的数据做为指针低地址，取出这个对应的数据，交换数据完成查表。加密

b. 线行混合层——进行ShiftRow和MixColumn运算： ShiftRow是一个字节换位。它将状态中的行按照不一样的偏移量进行循环移位，而这个偏移量也是根据Nb的不一样而选择的；在MixColumn变换中,把状态中的每一列看做GF(28)上的多项式a(x)与固定多项式c(x)相乘的结果。b(x)=c(x)*a(x)的系数这样计算:*运算不是普通的乘法运算,而是特殊的运算，即b(x)=c(x)·a(x)(mod x4+1)对于这个运算b0=02。a0+03。a1+a2+a3令xtime(a0)=02。a0其中，符号“。”表示模一个八次不可约多项式的同余乘法。对于逆变化,其矩阵C要改变成相应的D,即b(x)=d(x)＊a(x)。spa

c.密钥加层——进行AddRoundKey运算: 将圈密钥状态中的对应字节按位“异或”。设计

2.轮变化 :对不一样的分组长度，其对应的轮变化次数是不一样的 .3d

3.秘钥扩展:利用外部输入密钥K(密钥串的字数为Nk),经过密钥的扩展程序获得共计4(Nr+1)字的扩展密钥。它涉及以下三个模块:指针

① 位置变换(rotword)——把一个4字节的序列[A,B,C,D]变化成[B,C,D,A]；

② S盒变换(subword)——对一个4字节进行S盒代替；

③ 变换Rcon[i]——Rcon[i]表示32位比特字[xi-1,00,00,00]。这里的x是（02），如

Rcon[1]=[01000000]；Rcon[2]=[02000000]；Rcon[3]=[04000000]……

扩展密钥的生成：扩展密钥的前Nk个字就是外部密钥K；之后的字W[[ｉ]]等于它前一个字W[[i-1]]与前第Nk个字W[[i-Nk]]的“异或”,即W[[ｉ]]=W[[i-1]] W[[ｉ- Nk]]。可是若ｉ为Nk的倍数,则W[ｉ]=W[i-Nk] Subword(Rotword(W[[ｉ-1]])) Rcon[i/Nk]。

解密要比加密复杂和费时。

具体用法以及代码以下：

//加密
char miwen[1024*2] = "";//密文
unsigned char key[] = "20171102";
AES aesEncrypt(key);
CString strMingWen;
strPara = CStringA(strMingWen);
aesEncrypt.Bm53Cipher(strPara.c_str(), miwen);


//解密引擎
unsigned char key[] = "20171102";//key
AES aesEncrypt(key);
char mingwen[1024*2] = "";
CString strMiWen;
std::string strPara = CStringA(strMiWen);
aesEncrypt.Bm53InvCipher(strPara.c_str(), mingwen);

// AES.h: interface for the AES class.
//
//////////////////////////////////////////////////////////////////////

#if !defined(AFX_AES_H__24984881_87F5_447A_838A_57873C600813__INCLUDED_)
#define AFX_AES_H__24984881_87F5_447A_838A_57873C600813__INCLUDED_

#include <string.h>

#if _MSC_VER > 1000
#pragma once
#endif // _MSC_VER > 1000

class __declspec(dllexport) AES

{

public:
	AES(unsigned char* key);
	
	virtual ~AES();
	//加密整段文字
	void Bm53Cipher(const char *input,char *output);	
	void Bm53InvCipher(const char *input, char *output);
	void InvCipher(const char *input, char *output);
	
private:	
	unsigned char* Cipher(unsigned char* input);	
	unsigned char* InvCipher(unsigned char* input);
	void* Cipher(void* input, int length=0);
	void* InvCipher(void* input, int length);	
	void Cipher(char *input, char *output);	
	unsigned char Sbox[256];	
	unsigned char InvSbox[256];	
	unsigned char w[11][4][4];	
	void KeyExpansion(unsigned char* key, unsigned char w[][4][4]);	
	unsigned char FFmul(unsigned char a, unsigned char b);	
	void SubBytes(unsigned char state[][4]);
	void ShiftRows(unsigned char state[][4]);	
	void MixColumns(unsigned char state[][4]);	
	void AddRoundKey(unsigned char state[][4], unsigned char k[][4]);	
	void InvSubBytes(unsigned char state[][4]);	
	void InvShiftRows(unsigned char state[][4]);	
	void InvMixColumns(unsigned char state[][4]);
	int strToHex(const char *ch, char *hex);
	int hexToStr(const char *hex, char *ch);
	int ascillToValue(const char ch);
	char valueToHexCh(const int value);
	int getUCharLen(const unsigned char *uch);
	int strToUChar(const char *ch, unsigned char *uch);
	int ucharToStr(const unsigned char *uch, char *ch);
	int ucharToHex(const unsigned char *uch, char *hex);
	int hexToUChar(const char *hex, unsigned char *uch);
};


#endif // !defined(AFX_AES_H__24984881_87F5_447A_838A_57873C600813__INCLUDED_)

// AES.cpp: implementation of the AES class.
//
//////////////////////////////////////////////////////////////////////
#include "stdafx.h"
#include "stdio.h"
#include "memory.h"
#include "time.h"
#include "stdlib.h"
#include "AES.h"
//////////////////////////////////////////////////////////////////////
// Construction/Destruction
//////////////////////////////////////////////////////////////////////

AES::AES(unsigned char* key)

{

  unsigned char sBox[] =

  { /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */

    0x63,0x7c,0x77,0x7b,0xf2,0x6b,0x6f,0xc5,0x30,0x01,0x67,0x2b,0xfe,0xd7,0xab,0x76, /*0*/

    0xca,0x82,0xc9,0x7d,0xfa,0x59,0x47,0xf0,0xad,0xd4,0xa2,0xaf,0x9c,0xa4,0x72,0xc0, /*1*/

    0xb7,0xfd,0x93,0x26,0x36,0x3f,0xf7,0xcc,0x34,0xa5,0xe5,0xf1,0x71,0xd8,0x31,0x15, /*2*/

    0x04,0xc7,0x23,0xc3,0x18,0x96,0x05,0x9a,0x07,0x12,0x80,0xe2,0xeb,0x27,0xb2,0x75, /*3*/

    0x09,0x83,0x2c,0x1a,0x1b,0x6e,0x5a,0xa0,0x52,0x3b,0xd6,0xb3,0x29,0xe3,0x2f,0x84, /*4*/

    0x53,0xd1,0x00,0xed,0x20,0xfc,0xb1,0x5b,0x6a,0xcb,0xbe,0x39,0x4a,0x4c,0x58,0xcf, /*5*/

    0xd0,0xef,0xaa,0xfb,0x43,0x4d,0x33,0x85,0x45,0xf9,0x02,0x7f,0x50,0x3c,0x9f,0xa8, /*6*/

    0x51,0xa3,0x40,0x8f,0x92,0x9d,0x38,0xf5,0xbc,0xb6,0xda,0x21,0x10,0xff,0xf3,0xd2, /*7*/

    0xcd,0x0c,0x13,0xec,0x5f,0x97,0x44,0x17,0xc4,0xa7,0x7e,0x3d,0x64,0x5d,0x19,0x73, /*8*/

    0x60,0x81,0x4f,0xdc,0x22,0x2a,0x90,0x88,0x46,0xee,0xb8,0x14,0xde,0x5e,0x0b,0xdb, /*9*/

    0xe0,0x32,0x3a,0x0a,0x49,0x06,0x24,0x5c,0xc2,0xd3,0xac,0x62,0x91,0x95,0xe4,0x79, /*a*/

    0xe7,0xc8,0x37,0x6d,0x8d,0xd5,0x4e,0xa9,0x6c,0x56,0xf4,0xea,0x65,0x7a,0xae,0x08, /*b*/

    0xba,0x78,0x25,0x2e,0x1c,0xa6,0xb4,0xc6,0xe8,0xdd,0x74,0x1f,0x4b,0xbd,0x8b,0x8a, /*c*/

    0x70,0x3e,0xb5,0x66,0x48,0x03,0xf6,0x0e,0x61,0x35,0x57,0xb9,0x86,0xc1,0x1d,0x9e, /*d*/

    0xe1,0xf8,0x98,0x11,0x69,0xd9,0x8e,0x94,0x9b,0x1e,0x87,0xe9,0xce,0x55,0x28,0xdf, /*e*/

    0x8c,0xa1,0x89,0x0d,0xbf,0xe6,0x42,0x68,0x41,0x99,0x2d,0x0f,0xb0,0x54,0xbb,0x16 /*f*/

  };

  unsigned char invsBox[256] =

  { /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */

    0x52,0x09,0x6a,0xd5,0x30,0x36,0xa5,0x38,0xbf,0x40,0xa3,0x9e,0x81,0xf3,0xd7,0xfb, /*0*/

    0x7c,0xe3,0x39,0x82,0x9b,0x2f,0xff,0x87,0x34,0x8e,0x43,0x44,0xc4,0xde,0xe9,0xcb, /*1*/

    0x54,0x7b,0x94,0x32,0xa6,0xc2,0x23,0x3d,0xee,0x4c,0x95,0x0b,0x42,0xfa,0xc3,0x4e, /*2*/

    0x08,0x2e,0xa1,0x66,0x28,0xd9,0x24,0xb2,0x76,0x5b,0xa2,0x49,0x6d,0x8b,0xd1,0x25, /*3*/

    0x72,0xf8,0xf6,0x64,0x86,0x68,0x98,0x16,0xd4,0xa4,0x5c,0xcc,0x5d,0x65,0xb6,0x92, /*4*/

    0x6c,0x70,0x48,0x50,0xfd,0xed,0xb9,0xda,0x5e,0x15,0x46,0x57,0xa7,0x8d,0x9d,0x84, /*5*/

    0x90,0xd8,0xab,0x00,0x8c,0xbc,0xd3,0x0a,0xf7,0xe4,0x58,0x05,0xb8,0xb3,0x45,0x06, /*6*/

    0xd0,0x2c,0x1e,0x8f,0xca,0x3f,0x0f,0x02,0xc1,0xaf,0xbd,0x03,0x01,0x13,0x8a,0x6b, /*7*/

    0x3a,0x91,0x11,0x41,0x4f,0x67,0xdc,0xea,0x97,0xf2,0xcf,0xce,0xf0,0xb4,0xe6,0x73, /*8*/

    0x96,0xac,0x74,0x22,0xe7,0xad,0x35,0x85,0xe2,0xf9,0x37,0xe8,0x1c,0x75,0xdf,0x6e, /*9*/

    0x47,0xf1,0x1a,0x71,0x1d,0x29,0xc5,0x89,0x6f,0xb7,0x62,0x0e,0xaa,0x18,0xbe,0x1b, /*a*/

    0xfc,0x56,0x3e,0x4b,0xc6,0xd2,0x79,0x20,0x9a,0xdb,0xc0,0xfe,0x78,0xcd,0x5a,0xf4, /*b*/

    0x1f,0xdd,0xa8,0x33,0x88,0x07,0xc7,0x31,0xb1,0x12,0x10,0x59,0x27,0x80,0xec,0x5f, /*c*/

    0x60,0x51,0x7f,0xa9,0x19,0xb5,0x4a,0x0d,0x2d,0xe5,0x7a,0x9f,0x93,0xc9,0x9c,0xef, /*d*/

    0xa0,0xe0,0x3b,0x4d,0xae,0x2a,0xf5,0xb0,0xc8,0xeb,0xbb,0x3c,0x83,0x53,0x99,0x61, /*e*/

    0x17,0x2b,0x04,0x7e,0xba,0x77,0xd6,0x26,0xe1,0x69,0x14,0x63,0x55,0x21,0x0c,0x7d /*f*/

  };

  memcpy(Sbox, sBox, 256);

  memcpy(InvSbox, invsBox, 256);

  memset(w, 0, 176);

  KeyExpansion(key, w);

}



AES::~AES()

{



}



void AES::Cipher(char *input, char *output)
{
  unsigned char uch_input[1024];
  strToUChar(input, uch_input);
  Cipher(uch_input);
  ucharToHex(uch_input,output);
}


 /*********************************************
 * 函数名：  AES::Bm53Cipher
 * 描述：    整段文档加密
 * @参数：   char *input
 * @参数：   char *output
 * @返回值： void 
 *********************************************/
void AES::Bm53Cipher(const char *input,char *output)
{
	int nLen = strlen(input);
	char * newAlock = (char*)malloc(nLen+(16-nLen%16)+1);
	strcpy(newAlock,input);
	for (int n=0;n<(16-nLen%16);n++)
	{
		newAlock[nLen+n] = (16-nLen%16);
	}
	newAlock[nLen + (16-nLen%16)] = 0;
	int i=0,j=0;
	char block[17],e_block[33];
	while (newAlock[i]!='\0')
	{
		strncpy(block,newAlock+i,16);
		block[16] = '\0';
		Cipher(block,e_block);
		strncpy(output+j,e_block,32);
		i+=16;
		j+=32;
	}
	output[j]='\0';
	free(newAlock);
}


void AES::InvCipher(const char *input, char *output)
{
  unsigned char uch_input[1024];
  hexToUChar(input, uch_input);
  InvCipher(uch_input);
  ucharToStr(uch_input, output);
}
 /*********************************************
 * 函数名：  AES::Bm53InvCipher
 * 描述：    对整段文字解密
 * @参数：   char *input 16进制密文
 * @参数：   char *output 原文
 * @返回值： void 
 *********************************************/
void AES::Bm53InvCipher(const char *input, char *output)
{
	unsigned char *uch_input = (unsigned char *)malloc(1024*10);	
	unsigned char *uch_output = (unsigned char *)malloc(/*strlen(output)*/1024*10);
	memset(uch_input,0,sizeof(unsigned char)*1024*10);
	memset(uch_output,0,sizeof(unsigned char)*1024*10);
	hexToUChar(input, uch_input);
	int nBuf = 0;
	unsigned char ublock[16];
	int n= strlen(input);
	while(nBuf<(int)strlen(input)/2)
	{
		memcpy(ublock,uch_input+nBuf,16);
		InvCipher(ublock);
		memcpy(uch_output+nBuf,ublock,16);
		nBuf+=16;
	}
	uch_output[nBuf] = 0;//封闭字符串
	ucharToStr(uch_output,output);
	//剔除用于补充16字节的字符
	int nLen = strlen(output);
	for (n=nLen-1;n>=nLen-16;n--)
	{
		if (1<=output[n]&&16>=output[n])
		{
			output[n] = 0;
		}
		else
		{
			break;
		}
	}
}

unsigned char* AES::Cipher(unsigned char* input)
{
  unsigned char state[4][4];
  int i,r,c;
  for(r=0; r<4; r++)
  {
    for(c=0; c<4 ;c++)
    {
      state[r][c] = input[c*4+r];
    }
  }
  AddRoundKey(state,w[0]);
  for(i=1; i<=10; i++)
  {
    SubBytes(state);
    ShiftRows(state);
    if(i!=10)MixColumns(state);
    AddRoundKey(state,w[i]);
  }



  for(r=0; r<4; r++)
  {

    for(c=0; c<4 ;c++)

    {

      input[c*4+r] = state[r][c];

    }

  }


  input[16] = '\0';
  return input;

}



unsigned char* AES::InvCipher(unsigned char* input)

{

  unsigned char state[4][4];

  int i,r,c;



  for(r=0; r<4; r++)

  {

    for(c=0; c<4 ;c++)

    {

      state[r][c] = input[c*4+r];

    }

  }



  AddRoundKey(state, w[10]);

  for(i=9; i>=0; i--)

  {

    InvShiftRows(state);

    InvSubBytes(state);

    AddRoundKey(state, w[i]);

    if(i)

    {

      InvMixColumns(state);

    }

  }



  for(r=0; r<4; r++)

  {

    for(c=0; c<4 ;c++)

    {

      input[c*4+r] = state[r][c];

    }

  }



  return input;

}



void* AES::Cipher(void* input, int length)

{

  unsigned char* in = (unsigned char*) input;

  int i;

  if(!length)

  {

    while(*(in+length++));

    in = (unsigned char*) input;

  }

  for(i=0; i<length; i+=16)

  {

    Cipher(in+i);

  }

  return input;

}



void* AES::InvCipher(void* input, int length)

{

  unsigned char* in = (unsigned char*) input;

  int i;

  for(i=0; i<length; i+=16)

  {

    InvCipher(in+i);

  }

  return input;

}



void AES::KeyExpansion(unsigned char* key, unsigned char w[][4][4])

{

  int i,j,r,c;

  unsigned char rc[] = {0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36};

  int nKeyLen = strlen((const char*)key);

  for(r=0; r<4; r++)

  {

    for(c=0; c<4; c++)

    {
		int nNewIndex= r+c*4;

		if ( nKeyLen <= nNewIndex)
			w[0][r][c] = 0;
		else
			w[0][r][c] = key[nNewIndex];
    }

  }

  for(i=1; i<=10; i++)

  {

    for(j=0; j<4; j++)

    {

      unsigned char t[4];

      for(r=0; r<4; r++)

      {

        t[r] = j ? w[i][r][j-1] : w[i-1][r][3];

      }

      if(j == 0)

      {

        unsigned char temp = t[0];

        for(r=0; r<3; r++)

        {

          t[r] = Sbox[t[(r+1)%4]];

        }

        t[3] = Sbox[temp];

        t[0] ^= rc[i-1];

      }

      for(r=0; r<4; r++)

      {

        w[i][r][j] = w[i-1][r][j] ^ t[r];

      }

    }

  }

}



unsigned char AES::FFmul(unsigned char a, unsigned char b)

{

  unsigned char bw[4];

  unsigned char res=0;

  int i;

  bw[0] = b;

  for(i=1; i<4; i++)

  {

    bw[i] = bw[i-1]<<1;

    if(bw[i-1]&0x80)

    {

      bw[i]^=0x1b;

    }

  }

  for(i=0; i<4; i++)

  {

    if((a>>i)&0x01)

    {

      res ^= bw[i];

    }

  }

  return res;

}



void AES::SubBytes(unsigned char state[][4])

{

  int r,c;

  for(r=0; r<4; r++)

  {

    for(c=0; c<4; c++)

    {

      state[r][c] = Sbox[state[r][c]];

    }

  }

}



void AES::ShiftRows(unsigned char state[][4])

{

  unsigned char t[4];

  int r,c;

  for(r=1; r<4; r++)

  {

    for(c=0; c<4; c++)

    {

      t[c] = state[r][(c+r)%4];

    }

    for(c=0; c<4; c++)

    {

      state[r][c] = t[c];

    }

  }

}



void AES::MixColumns(unsigned char state[][4])

{

  unsigned char t[4];

  int r,c;

  for(c=0; c< 4; c++)

  {

    for(r=0; r<4; r++)

    {

      t[r] = state[r][c];

    }

    for(r=0; r<4; r++)

    {

      state[r][c] = FFmul(0x02, t[r])

            ^ FFmul(0x03, t[(r+1)%4])

            ^ FFmul(0x01, t[(r+2)%4])

            ^ FFmul(0x01, t[(r+3)%4]);

    }

  }

}



void AES::AddRoundKey(unsigned char state[][4], unsigned char k[][4])

{

  int r,c;

  for(c=0; c<4; c++)

  {

    for(r=0; r<4; r++)

    {

      state[r][c] ^= k[r][c];

    }

  }

}



void AES::InvSubBytes(unsigned char state[][4])

{

  int r,c;

  for(r=0; r<4; r++)

  {

    for(c=0; c<4; c++)

    {

      state[r][c] = InvSbox[state[r][c]];

    }

  }

}



void AES::InvShiftRows(unsigned char state[][4])

{

  unsigned char t[4];

  int r,c;

  for(r=1; r<4; r++)

  {

    for(c=0; c<4; c++)

    {

      t[c] = state[r][(c-r+4)%4];

    }

    for(c=0; c<4; c++)

    {

      state[r][c] = t[c];

    }

  }

}



void AES::InvMixColumns(unsigned char state[][4])

{

  unsigned char t[4];

  int r,c;

  for(c=0; c< 4; c++)

  {

    for(r=0; r<4; r++)

    {

      t[r] = state[r][c];

    }

    for(r=0; r<4; r++)

    {

      state[r][c] = FFmul(0x0e, t[r])

            ^ FFmul(0x0b, t[(r+1)%4])

            ^ FFmul(0x0d, t[(r+2)%4])

            ^ FFmul(0x09, t[(r+3)%4]);

    }

  }

}



int AES::getUCharLen(const unsigned char *uch)

{

  int len = 0;

  while(*uch++)

    ++len;



  return len;

}



int AES::ucharToHex(const unsigned char *uch, char *hex)

{

  int high,low;

  int tmp = 0;

  if(uch == NULL || hex == NULL){

    return -1;

  }


  /*不可如此判断，不然当中间为0时会致使加密出错，如“双顶双抱” 
  if(getUCharLen(uch) == 0){

    return -2;

  }*/



  //while(*uch){
  //不可经过字符串是否为0来判断，不然当中间为0时会致使加密出错，如“绝缘子” 
  //而在Cipher函数中己明确将[16]处设置为0，仍须要进一步测试
  for (int nIndex = 0; nIndex < 16; ++nIndex)
  {
    tmp = (int)*uch;

    high = tmp >> 4;

    low = tmp & 15;

    *hex++ = valueToHexCh(high); //先写高字节

    *hex++ = valueToHexCh(low); //其次写低字节

    uch++;
  }

  *hex = '\0';

  return 0;

}



int AES::hexToUChar(const char *hex, unsigned char *uch)

{

  int high,low;

  int tmp = 0;

  if(hex == NULL || uch == NULL){

    return -1;

  }



  if(strlen(hex) %2 == 1){

    return -2;

  }



  while(*hex){

    high = ascillToValue(*hex);

    if(high < 0){

      *uch = '\0';

      return -3;

    }

    hex++; //指针移动到下一个字符上

    low = ascillToValue(*hex);

    if(low < 0){

      *uch = '\0';

      return -3;

    }

    tmp = (high << 4) + low;

    *uch++ = tmp;

    hex++;

  }

  *uch = (int)'\0';

  return 0;

}



int AES::strToUChar(const char *ch, unsigned char *uch)

{

  int tmp = 0;

  if(ch == NULL || uch == NULL)

    return -1;

  if(strlen(ch) == 0)

    return -2;



  while(*ch){

    tmp = (int)*ch;

    *uch++ = tmp;

    ch++;

  }

  *uch = (int)'\0';

  return 0;

}



int AES::ucharToStr(const unsigned char *uch, char *ch)
{
  int tmp = 0;
  if(uch == NULL || ch == NULL)
    return -1;
  while(*uch){
    tmp = (int)*uch;
    *ch++ = (char)tmp;
    uch++;
  }

  *ch = '\0';
  return 0;
}



int AES::strToHex(const char *ch, char *hex)

{

  int high,low;

  int tmp = 0;

  if(ch == NULL || hex == NULL){

    return -1;

  }



  if(strlen(ch) == 0){

    return -2;

  }



  while(*ch){

    tmp = (int)*ch;

    high = tmp >> 4;

    low = tmp & 15;

    *hex++ = valueToHexCh(high); //先写高字节

    *hex++ = valueToHexCh(low); //其次写低字节

    ch++;

  }

  *hex = '\0';

  return 0;

}



int AES::hexToStr(const char *hex, char *ch)

{

  int high,low;

  int tmp = 0;

  if(hex == NULL || ch == NULL){

    return -1;

  }



  if(strlen(hex) %2 == 1){

    return -2;

  }



  while(*hex){

    high = ascillToValue(*hex);

    if(high < 0){

      *ch = '\0';

      return -3;

    }

    hex++; //指针移动到下一个字符上

    low = ascillToValue(*hex);

    if(low < 0){

      *ch = '\0';

      return -3;

    }

    tmp = (high << 4) + low;

    *ch++ = (char)tmp;

    hex++;

  }

  *ch = '\0';

  return 0;

}



int AES::ascillToValue(const char ch){

  int result = 0;

  //获取16进制的高字节位数据

  if(ch >= '0' && ch <= '9'){

    result = (int)(ch - '0');

  }

  else if(ch >= 'a' && ch <= 'z'){

    result = (int)(ch - 'a') + 10;

  }

  else if(ch >= 'A' && ch <= 'Z'){

    result = (int)(ch - 'A') + 10;

  }

  else{

    result = -1;

  }

  return result;

}



char AES::valueToHexCh(const int value)

{

  char result = '\0';

  if(value >= 0 && value <= 9){

    result = (char)(value + 48); //48为ascii编码的‘0’字符编码值

  }

  else if(value >= 10 && value <= 15){

    result = (char)(value - 10 + 65); //减去10则找出其在16进制的偏移量，65为ascii的'A'的字符编码值

  }

  else{

    ;

  }

  return result;
}