c语言md5算法实现
#include<stdio.h>
#include<stdlib.h>
#defineARR_LEN100
#defineF(x,y,z)((x&y)|(~x&z))
#defineG(x,y,z)((x&z)|(y&~z))
#defineH(x,y,z)(x^y^z)
#defineI(x,y,z)(y^(x|~z))
#defineROTATE_LEFT(x,n)((x<<n)|(x>>(32-n)))
#defineFF(a,b,c,d,x,s,ac)
{
a+=F(b,c,d)+x+ac;
a=ROTATE_LEFT(a,s);
a+=b;
}
#defineGG(a,b,c,d,x,s,ac)
{
a+=G(b,c,d)+x+ac;
a=ROTATE_LEFT(a,s);
a+=b;
}
#defineHH(a,b,c,d,x,s,ac)
{
a+=H(b,c,d)+x+ac;
a=ROTATE_LEFT(a,s);
a+=b;
}
#defineII(a,b,c,d,x,s,ac)
{
a+=I(b,c,d)+x+ac;
a=ROTATE_LEFT(a,s);
a+=b;
}
typedefstruct{
unsignedintcount[2];
unsignedintstate[4];
unsignedcharbuffer[64];
}MD5_CTX;
voidMD5Init(MD5_CTX*context);
voidMD5Update(MD5_CTX*context,unsignedchar*input,unsignedintinputlen);
voidMD5Final(MD5_CTX*context,unsignedchardigest[16]);
voidMD5Transform(unsignedintstate[4],unsignedcharblock[64]);
voidMD5Encode(unsignedchar*output,unsignedint*input,unsignedintlen);
voidMD5Decode(unsignedint*output,unsignedchar*input,unsignedintlen);
unsignedcharPADDING[]={
0x80,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
};
voidMD5Init(MD5_CTX*context){
context->count[0]=0;
context->count[1]=0;
context->state[0]=0x67452301;
context->state[1]=0xEFCDAB89;
context->state[2]=0x98BADCFE;
context->state[3]=0x10325476;
}
voidMD5Update(MD5_CTX*context,unsignedchar*input,unsignedintinputlen){
unsignedinti=0,index=0,partlen=0;
index=(context->count[0]>>3)&0x3F;
partlen=64-index;
context->count[0]+=inputlen<<3;
if(context->count[0]<(inputlen<<3))
context->count[1]++;
context->count[1]+=inputlen>>29;
if(inputlen>=partlen){
memcpy(&context->buffer[index],input,partlen);
MD5Transform(context->state,context->buffer);
for(i=partlen;i+64<=inputlen;i+=64)
MD5Transform(context->state,&input[i]);
index=0;
}
else{
i=0;
}
memcpy(&context->buffer[index],&input[i],inputlen-i);
}
voidMD5Final(MD5_CTX*context,unsignedchardigest[16]){
unsignedintindex=0,padlen=0;
unsignedcharbits[8];
index=(context->count[0]>>3)&0x3F;
padlen=(index<56)?(56-index):(120-index);
MD5Encode(bits,context->count,8);
MD5Update(context,PADDING,padlen);
MD5Update(context,bits,8);
MD5Encode(digest,context->state,16);
}
voidMD5Encode(unsignedchar*output,unsignedint*input,unsignedintlen){
unsignedinti=0,j=0;
while(j<len){
output[j]=input[i]&0xFF;
output[j+1]=(input[i]>>8)&0xFF;
output[j+2]=(input[i]>>16)&0xFF;
output[j+3]=(input[i]>>24)&0xFF;
i++;
j+=4;
}
}
voidMD5Decode(unsignedint*output,unsignedchar*input,unsignedintlen){
unsignedinti=0,j=0;
while(j<len){
output[i]=(input[j])|
(input[j+1]<<8)|
(input[j+2]<<16)|
(input[j+3]<<24);
i++;
j+=4;
}
}
voidMD5Transform(unsignedintstate[4],unsignedcharblock[64]){
unsignedinta=state[0];
unsignedintb=state[1];
unsignedintc=state[2];
unsignedintd=state[3];
unsignedintx[64];
MD5Decode(x,block,64);
FF(a,b,c,d,x[0],7,0xd76aa478);/*1*/
FF(d,a,b,c,x[1],12,0xe8c7b756);/*2*/
FF(c,d,a,b,x[2],17,0x242070db);/*3*/
FF(b,c,d,a,x[3],22,0xc1bdceee);/*4*/
FF(a,b,c,d,x[4],7,0xf57c0faf);/*5*/
FF(d,a,b,c,x[5],12,0x4787c62a);/*6*/
FF(c,d,a,b,x[6],17,0xa8304613);/*7*/
FF(b,c,d,a,x[7],22,0xfd469501);/*8*/
FF(a,b,c,d,x[8],7,0x698098d8);/*9*/
FF(d,a,b,c,x[9],12,0x8b44f7af);/*10*/
FF(c,d,a,b,x[10],17,0xffff5bb1);/*11*/
FF(b,c,d,a,x[11],22,0x895cd7be);/*12*/
FF(a,b,c,d,x[12],7,0x6b901122);/*13*/
FF(d,a,b,c,x[13],12,0xfd987193);/*14*/
FF(c,d,a,b,x[14],17,0xa679438e);/*15*/
FF(b,c,d,a,x[15],22,0x49b40821);/*16*/
/*Round2*/
GG(a,b,c,d,x[1],5,0xf61e2562);/*17*/
GG(d,a,b,c,x[6],9,0xc040b340);/*18*/
GG(c,d,a,b,x[11],14,0x265e5a51);/*19*/
GG(b,c,d,a,x[0],20,0xe9b6c7aa);/*20*/
GG(a,b,c,d,x[5],5,0xd62f105d);/*21*/
GG(d,a,b,c,x[10],9,0x2441453);/*22*/
GG(c,d,a,b,x[15],14,0xd8a1e681);/*23*/
GG(b,c,d,a,x[4],20,0xe7d3fbc8);/*24*/
GG(a,b,c,d,x[9],5,0x21e1cde6);/*25*/
GG(d,a,b,c,x[14],9,0xc33707d6);/*26*/
GG(c,d,a,b,x[3],14,0xf4d50d87);/*27*/
GG(b,c,d,a,x[8],20,0x455a14ed);/*28*/
GG(a,b,c,d,x[13],5,0xa9e3e905);/*29*/
GG(d,a,b,c,x[2],9,0xfcefa3f8);/*30*/
GG(c,d,a,b,x[7],14,0x676f02d9);/*31*/
GG(b,c,d,a,x[12],20,0x8d2a4c8a);/*32*/
/*Round3*/
HH(a,b,c,d,x[5],4,0xfffa3942);/*33*/
HH(d,a,b,c,x[8],11,0x8771f681);/*34*/
HH(c,d,a,b,x[11],16,0x6d9d6122);/*35*/
HH(b,c,d,a,x[14],23,0xfde5380c);/*36*/
HH(a,b,c,d,x[1],4,0xa4beea44);/*37*/
HH(d,a,b,c,x[4],11,0x4bdecfa9);/*38*/
HH(c,d,a,b,x[7],16,0xf6bb4b60);/*39*/
HH(b,c,d,a,x[10],23,0xbebfbc70);/*40*/
HH(a,b,c,d,x[13],4,0x289b7ec6);/*41*/
HH(d,a,b,c,x[0],11,0xeaa127fa);/*42*/
HH(c,d,a,b,x[3],16,0xd4ef3085);/*43*/
HH(b,c,d,a,x[6],23,0x4881d05);/*44*/
HH(a,b,c,d,x[9],4,0xd9d4d039);/*45*/
HH(d,a,b,c,x[12],11,0xe6db99e5);/*46*/
HH(c,d,a,b,x[15],16,0x1fa27cf8);/*47*/
HH(b,c,d,a,x[2],23,0xc4ac5665);/*48*/
/*Round4*/
II(a,b,c,d,x[0],6,0xf4292244);/*49*/
II(d,a,b,c,x[7],10,0x432aff97);/*50*/
II(c,d,a,b,x[14],15,0xab9423a7);/*51*/
II(b,c,d,a,x[5],21,0xfc93a039);/*52*/
II(a,b,c,d,x[12],6,0x655b59c3);/*53*/
II(d,a,b,c,x[3],10,0x8f0ccc92);/*54*/
II(c,d,a,b,x[10],15,0xffeff47d);/*55*/
II(b,c,d,a,x[1],21,0x85845dd1);/*56*/
II(a,b,c,d,x[8],6,0x6fa87e4f);/*57*/
II(d,a,b,c,x[15],10,0xfe2ce6e0);/*58*/
II(c,d,a,b,x[6],15,0xa3014314);/*59*/
II(b,c,d,a,x[13],21,0x4e0811a1);/*60*/
II(a,b,c,d,x[4],6,0xf7537e82);/*61*/
II(d,a,b,c,x[11],10,0xbd3af235);/*62*/
II(c,d,a,b,x[2],15,0x2ad7d2bb);/*63*/
II(b,c,d,a,x[9],21,0xeb86d391);/*64*/
state[0]+=a;
state[1]+=b;
state[2]+=c;
state[3]+=d;
}
intmain(intargc,char*argv[]){
inti;
unsignedcharencrypt[ARR_LEN];
unsignedchardecrypt[16];
MD5_CTXmd5;
printf("【测试1】 ");
printf("加密前：Bai ");
printf("加密后： ");
printf(" ");
printf("【测试2】 ");
printf("加密前：Bihaifeng ");
printf("加密后： ");
printf(" ");
printf("====================================================== ");
printf("请输入需MD5加密的字符串： ");
gets(encrypt);
printf(" ");
printf("====================================================== ");
MD5Init(&md5);
MD5Update(&md5,encrypt,strlen((char*)encrypt));
MD5Final(&md5,decrypt);
printf("加密前：%s 加密后：",encrypt);
for(i=0;i<16;i++){
printf("%02x",decrypt[i]);
}
printf(" ");
getch();
return0;
}
运行结果
以上源代码非原创~~
❷ 如何对字符串进行MD5加密,用C语言实现,给出源代码和加密函数
/*四个32bits数,用于存放最终计算得到的消息摘要.当消息长度>512bits时,也用于存放每个512bits的中间结果*/ UINT4 state[4]; /*存储原始信息的bits数长度,不包括填充的bits,最长为2^64 bits*/ UINT4 count[2]; /*存放输入的信息的缓冲区,512bits*/ unsigned char buffer[64];} MD5_CTX;static void MD5Transform(UINT4[4], unsigned char[64]); static void Encode(unsigned char *, UINT4 *, unsigned int); static void Decode(UINT4 *, unsigned char *, unsigned int);/*用于bits填充的缓冲区,当欲加密的信息的bits数被512除其余数为448时,需要填充的bits的最大值为512=64*8*/ static unsigned char PADDING[64] = { 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};/*接下来的这几个宏定义是md5算法规定的,就是对信息进行md5加密都要做的运算*/ #define F(x, y, z) (((x) & (y)) | ((~x) & (z))) #define G(x, y, z) (((x) & (z)) | ((y) & (~z))) #define H(x, y, z) ((x) ^ (y) ^ (z)) #define I(x, y, z) ((y) ^ ((x) | (~z))) #define ROTATE_LEFT(x, n) (((x) << (n)) | ((x) >> (32-(n)))) #define FF(a, b, c, d, x, s, ac) {\ (a) += F ((b), (c), (d)) + (x) + (UINT4)(ac);\ (a) = ROTATE_LEFT ((a), (s));\ (a) += (b);\}#define GG(a, b, c, d, x, s, ac) {\ (a) += G ((b), (c), (d)) + (x) + (UINT4)(ac);\ (a) = ROTATE_LEFT ((a), (s));\ (a) += (b);\}#define HH(a, b, c, d, x, s, ac) {\ (a) += H ((b), (c), (d)) + (x) + (UINT4)(ac);\ (a) = ROTATE_LEFT ((a), (s));\ (a) += (b);\}#define II(a, b, c, d, x, s, ac) {\ (a) += I ((b), (c), (d)) + (x) + (UINT4)(ac);\
❸ md5是什么 如何计算MD5
MD5即Message-Digest Algorithm 5（信息-摘要算法5），用于确保信息传输完整一致。是计算机广泛使用的杂凑算法之一（又译摘要算法、哈希算法），主流编程语言普遍已有MD5实现。
MD5算法具有以下特点：
1、压缩性：任意长度的数据，算出的MD5值长度都是固定的。
2、容易计算：从原数据计算出MD5值很容易。
3、抗修改性：对原数据进行任何改动，哪怕只修改1个字节，所得到的MD5值都有很大区别。
4、强抗碰撞：已知原数据和其MD5值，想找到一个具有相同MD5值的数据（即伪造数据）是非常困难的。
MD5的作用是让大容量信息在用数字签名软件签署私人密钥前被"压缩"成一种保密的格式（就是把一个任意长度的字节串变换成一定长的16进制数字串）。
大家都知道，地球上任何人都有自己独一无二的指纹，这常常成为司法机关鉴别罪犯身份最值得信赖的方法；与之类似，MD5就可以为任何文件（不管其大小、格式、数量）产生一个同样独一无二的MD5“数字指纹”，如果任何人对文件做了任何改动，其MD5也就是对应的“数字指纹”都会发生变化。
❹ 求MD5加密算法的C语言源码
（转载） #include <stdio.h> #include <stdlib.h> #include <memory.h> #include <time.h> #include <errno.h> #include <string.h> #include <sys/socket.h> #include <sys/types.h> #include <netinet/in.h> #include <arpa/inet.h> #include <netdb.h> #include "../md5/md5.h" #define T1 0xd76aa478 #define T2 0xe8c7b756 #define T3 0x242070db #define T4 0xc1bdceee #define T5 0xf57c0faf #define T6 0x4787c62a #define T7 0xa8304613 #define T8 0xfd469501 #define T9 0x698098d8 #define T10 0x8b44f7af #define T11 0xffff5bb1 #define T12 0x895cd7be #define T13 0x6b901122 #define T14 0xfd987193 #define T15 0xa679438e #define T16 0x49b40821 #define T17 0xf61e2562 #define T18 0xc040b340 #define T19 0x265e5a51 #define T20 0xe9b6c7aa #define T21 0xd62f105d #define T22 0x02441453 #define T23 0xd8a1e681 #define T24 0xe7d3fbc8 #define T25 0x21e1cde6 #define T26 0xc33707d6 #define T27 0xf4d50d87 #define T28 0x455a14ed #define T29 0xa9e3e905 #define T30 0xfcefa3f8 #define T31 0x676f02d9 #define T32 0x8d2a4c8a #define T33 0xfffa3942 #define T34 0x8771f681 #define T35 0x6d9d6122 #define T36 0xfde5380c #define T37 0xa4beea44 #define T38 0x4bdecfa9 #define T39 0xf6bb4b60 #define T40 0xbebfbc70 #define T41 0x289b7ec6 #define T42 0xeaa127fa #define T43 0xd4ef3085 #define T44 0x04881d05 #define T45 0xd9d4d039 #define T46 0xe6db99e5 #define T47 0x1fa27cf8 #define T48 0xc4ac5665 #define T49 0xf4292244 #define T50 0x432aff97 #define T51 0xab9423a7 #define T52 0xfc93a039 #define T53 0x655b59c3 #define T54 0x8f0ccc92 #define T55 0xffeff47d #define T56 0x85845dd1 #define T57 0x6fa87e4f #define T58 0xfe2ce6e0 #define T59 0xa3014314 #define T60 0x4e0811a1 #define T61 0xf7537e82 #define T62 0xbd3af235 #define T63 0x2ad7d2bb #define T64 0xeb86d391 static void md5_process(md5_state_t *pms, const md5_byte_t *data /*[64]*/) { md5_word_t a = pms->abcd[0], b = pms->abcd[1], c = pms->abcd[2], d = pms->abcd[3]; md5_word_t t; #ifndef ARCH_IS_BIG_ENDIAN # define ARCH_IS_BIG_ENDIAN 1 /* slower, default implementation */ #endif #if ARCH_IS_BIG_ENDIAN /* * On big-endian machines, we must arrange the bytes in the right * order. (This also works on machines of unknown byte order.) */ md5_word_t X[16]; const md5_byte_t *xp = data; int i; for (i = 0; i < 16; i, xp = 4) X[i] = xp[0] (xp[1] << 8) (xp[2] << 16) (xp[3] << 24); #else /* !ARCH_IS_BIG_ENDIAN */ /* * On little-endian machines, we can process properly aligned data * without ing it. */ md5_word_t xbuf[16]; const md5_word_t *X; if (!((data - (const md5_byte_t *)0) & 3)) { /* data are properly aligned */ X = (const md5_word_t *)data; } else { /* not aligned */ memcpy(xbuf, data, 64); X = xbuf; } #endif #define ROTATE_LEFT(x, n) (((x) << (n)) | ((x) >> (32 - (n)))) /* Round 1. */ /* Let [abcd k s i] denote the operation a = b ((a F(b,c,d) X[k] T[i]) <<< s). */ #define F(x, y, z) (((x) & (y)) | (~(x) & (z))) #define SET(a, b, c, d, k, s, Ti)\ t = a F(b,c,d) X[k] Ti;\ a = ROTATE_LEFT(t, s) b /* Do the following 16 operations. */ SET(a, b, c, d, 0, 7, T1); SET(d, a, b, c, 1, 12, T2); SET(c, d, a, b, 2, 17, T3); SET(b, c, d, a, 3, 22, T4); SET(a, b, c, d, 4, 7, T5); SET(d, a, b, c, 5, 12, T6); SET(c, d, a, b, 6, 17, T7); SET(b, c, d, a, 7, 22, T8); SET(a, b, c, d, 8, 7, T9); SET(d, a, b, c, 9, 12, T10); SET(c, d, a, b, 10, 17, T11); SET(b, c, d, a, 11, 22, T12); SET(a, b, c, d, 12, 7, T13); SET(d, a, b, c, 13, 12, T14); SET(c, d, a, b, 14, 17, T15); SET(b, c, d, a, 15, 22, T16); #undef SET /* Round 2. */ /* Let [abcd k s i] denote the operation a = b ((a G(b,c,d) X[k] T[i]) <<< s). */ #define G(x, y, z) (((x) & (z)) | ((y) & ~(z))) #define SET(a, b, c, d, k, s, Ti)\ t = a G(b,c,d) X[k] Ti;\ a = ROTATE_LEFT(t, s) b /* Do the following 16 operations. */ SET(a, b, c, d, 1, 5, T17); SET(d, a, b, c, 6, 9, T18); SET(c, d, a, b, 11, 14, T19); SET(b, c, d, a, 0, 20, T20); SET(a, b, c, d, 5, 5, T21); SET(d, a, b, c, 10, 9, T22); SET(c, d, a, b, 15, 14, T23); SET(b, c, d, a, 4, 20, T24); SET(a, b, c, d, 9, 5, T25); SET(d, a, b, c, 14, 9, T26); SET(c, d, a, b, 3, 14, T27); SET(b, c, d, a, 8, 20, T28); SET(a, b, c, d, 13, 5, T29); SET(d, a, b, c, 2, 9, T30); SET(c, d, a, b, 7, 14, T31); SET(b, c, d, a, 12, 20, T32); #undef SET
❺ 如何用C语言实现MD5算法计算一个文本的消息摘要
MD5是不可能逆向的。
王教授的碰撞法是利用了MD5或者SHA1算法的一个特性，
根据MD5和SHA1等Hash算法的特点，因为他们是任意长度的字符串变成固定长度的摘要信息。
那么这里就有可能发生一个问题，就是不同的字符串在理论上是有可能产生相同的摘要信息。
王教授所谓的碰撞法，碰撞的就是不同的字符串所产生的摘要信息是一样的那些字符串。因此得名碰撞法。
碰撞就是体现在这里。没有什么其它的传神的东西了。根据SHA1和MD5等Hash算法，在设计时候，设计这个算法的人认为不同的字符串要产生相同结果的摘要信息的可能性几乎为零。而王教授则证明了SHA1和MD5等Hash算法产生的摘要信息规则是可以在比较短时间内被破解的。这样一来，原始数据的
Integrity
就被打破了。
所谓的破解，也就是体现在这里。
至于破解工具，下面的地址提供一些免费的破解服务，能破解一些简单的密码，其实都是采用字典或暴力破解。
www.cmd5.com
www.xmd5.org
我有时去破解一些常用的密码，有一定的成功率
❻ C语言下对字符串进行MD5加密
怎么发给你？
md5.h
//===================================================
#ifndef MD5_H
#define MD5_H
#include <string>
#include <fstream>
/* Type define */
typedef unsigned char byte;
typedef unsigned int uint32;
using std::string;
using std::ifstream;
/* MD5 declaration. */
class MD5 {
public:
MD5();
MD5(const void* input, size_t length);
MD5(const string& str);
MD5(ifstream& in);
void update(const void* input, size_t length);
void update(const string& str);
void update(ifstream& in);
const byte* digest();
string toString();
void reset();
private:
void update(const byte* input, size_t length);
void final();
void transform(const byte block[64]);
void encode(const uint32* input, byte* output, size_t length);
void decode(const byte* input, uint32* output, size_t length);
string bytesToHexString(const byte* input, size_t length);
/* class unable */
MD5(const MD5&);
MD5& operator=(const MD5&);
private:
uint32 _state[4]; /* state (ABCD) */
uint32 _count[2]; /* number of bits, molo 2^64 (low-order word first) */
byte _buffer[64]; /* input buffer */
byte _digest[16]; /* message digest */
bool _finished; /* calculate finished ? */
static const byte PADDING[64]; /* padding for calculate */
static const char HEX[16];
enum { BUFFER_SIZE = 1024 };
};
#endif /*MD5_H*/
md5.cpp
//==============================================
#include "md5.h"
using namespace std;
/* Constants for MD5Transform routine. */
#define S11 7
#define S12 12
#define S13 17
#define S14 22
#define S21 5
#define S22 9
#define S23 14
#define S24 20
#define S31 4
#define S32 11
#define S33 16
#define S34 23
#define S41 6
#define S42 10
#define S43 15
#define S44 21
/* F, G, H and I are basic MD5 functions.
*/
#define F(x, y, z) (((x) & (y)) | ((~x) & (z)))
#define G(x, y, z) (((x) & (z)) | ((y) & (~z)))
#define H(x, y, z) ((x) ^ (y) ^ (z))
#define I(x, y, z) ((y) ^ ((x) | (~z)))
/* ROTATE_LEFT rotates x left n bits.
*/
#define ROTATE_LEFT(x, n) (((x) << (n)) | ((x) >> (32-(n))))
/* FF, GG, HH, and II transformations for rounds 1, 2, 3, and 4.
Rotation is separate from addition to prevent recomputation.
*/
#define FF(a, b, c, d, x, s, ac) { \
(a) += F ((b), (c), (d)) + (x) + ac; \
(a) = ROTATE_LEFT ((a), (s)); \
(a) += (b); \
}
#define GG(a, b, c, d, x, s, ac) { \
(a) += G ((b), (c), (d)) + (x) + ac; \
(a) = ROTATE_LEFT ((a), (s)); \
(a) += (b); \
}
#define HH(a, b, c, d, x, s, ac) { \
(a) += H ((b), (c), (d)) + (x) + ac; \
(a) = ROTATE_LEFT ((a), (s)); \
(a) += (b); \
}
#define II(a, b, c, d, x, s, ac) { \
(a) += I ((b), (c), (d)) + (x) + ac; \
(a) = ROTATE_LEFT ((a), (s)); \
(a) += (b); \
}
const byte MD5::PADDING[64] = { 0x80 };
const char MD5::HEX[16] = {
'0', '1', '2', '3',
'4', '5', '6', '7',
'8', '9', 'a', 'b',
'c', 'd', 'e', 'f'
};
/* Default construct. */
MD5::MD5() {
reset();
}
/* Construct a MD5 object with a input buffer. */
MD5::MD5(const void* input, size_t length) {
reset();
update(input, length);
}
/* Construct a MD5 object with a string. */
MD5::MD5(const string& str) {
reset();
update(str);
}
/* Construct a MD5 object with a file. */
MD5::MD5(ifstream& in) {
reset();
update(in);
}
/* Return the message-digest */
const byte* MD5::digest() {
if (!_finished) {
_finished = true;
final();
}
return _digest;
}
/* Reset the calculate state */
void MD5::reset() {
_finished = false;
/* reset number of bits. */
_count[0] = _count[1] = 0;
/* Load magic initialization constants. */
_state[0] = 0x67452301;
_state[1] = 0xefcdab89;
_state[2] = 0x98badcfe;
_state[3] = 0x10325476;
}
/* Updating the context with a input buffer. */
void MD5::update(const void* input, size_t length) {
update((const byte*)input, length);
}
/* Updating the context with a string. */
void MD5::update(const string& str) {
update((const byte*)str.c_str(), str.length());
}
/* Updating the context with a file. */
void MD5::update(ifstream& in) {
if (!in) {
return;
}
std::streamsize length;
char buffer[BUFFER_SIZE];
while (!in.eof()) {
in.read(buffer, BUFFER_SIZE);
length = in.gcount();
if (length > 0) {
update(buffer, length);
}
}
in.close();
}
/* MD5 block update operation. Continues an MD5 message-digest
operation, processing another message block, and updating the
context.
*/
void MD5::update(const byte* input, size_t length) {
uint32 i, index, partLen;
_finished = false;
/* Compute number of bytes mod 64 */
index = (uint32)((_count[0] >> 3) & 0x3f);
/* update number of bits */
if ((_count[0] += ((uint32)length << 3)) < ((uint32)length << 3)) {
++_count[1];
}
_count[1] += ((uint32)length >> 29);
partLen = 64 - index;
/* transform as many times as possible. */
if (length >= partLen) {
memcpy(&_buffer[index], input, partLen);
transform(_buffer);
for (i = partLen; i + 63 < length; i += 64) {
transform(&input[i]);
}
index = 0;
} else {
i = 0;
}
/* Buffer remaining input */
memcpy(&_buffer[index], &input[i], length - i);
}
/* MD5 finalization. Ends an MD5 message-_digest operation, writing the
the message _digest and zeroizing the context.
*/
void MD5::final() {
byte bits[8];
uint32 oldState[4];
uint32 oldCount[2];
uint32 index, padLen;
/* Save current state and count. */
memcpy(oldState, _state, 16);
memcpy(oldCount, _count, 8);
/* Save number of bits */
encode(_count, bits, 8);
/* Pad out to 56 mod 64. */
index = (uint32)((_count[0] >> 3) & 0x3f);
padLen = (index < 56) ? (56 - index) : (120 - index);
update(PADDING, padLen);
/* Append length (before padding) */
update(bits, 8);
/* Store state in digest */
encode(_state, _digest, 16);
/* Restore current state and count. */
memcpy(_state, oldState, 16);
memcpy(_count, oldCount, 8);
}
/* MD5 basic transformation. Transforms _state based on block. */
void MD5::transform(const byte block[64]) {
uint32 a = _state[0], b = _state[1], c = _state[2], d = _state[3], x[16];
decode(block, x, 64);
/* Round 1 */
FF (a, b, c, d, x[ 0], S11, 0xd76aa478); /* 1 */
FF (d, a, b, c, x[ 1], S12, 0xe8c7b756); /* 2 */
FF (c, d, a, b, x[ 2], S13, 0x242070db); /* 3 */
FF (b, c, d, a, x[ 3], S14, 0xc1bdceee); /* 4 */
FF (a, b, c, d, x[ 4], S11, 0xf57c0faf); /* 5 */
FF (d, a, b, c, x[ 5], S12, 0x4787c62a); /* 6 */
FF (c, d, a, b, x[ 6], S13, 0xa8304613); /* 7 */
FF (b, c, d, a, x[ 7], S14, 0xfd469501); /* 8 */
FF (a, b, c, d, x[ 8], S11, 0x698098d8); /* 9 */
FF (d, a, b, c, x[ 9], S12, 0x8b44f7af); /* 10 */
FF (c, d, a, b, x[10], S13, 0xffff5bb1); /* 11 */
FF (b, c, d, a, x[11], S14, 0x895cd7be); /* 12 */
FF (a, b, c, d, x[12], S11, 0x6b901122); /* 13 */
FF (d, a, b, c, x[13], S12, 0xfd987193); /* 14 */
FF (c, d, a, b, x[14], S13, 0xa679438e); /* 15 */
FF (b, c, d, a, x[15], S14, 0x49b40821); /* 16 */
/* Round 2 */
GG (a, b, c, d, x[ 1], S21, 0xf61e2562); /* 17 */
GG (d, a, b, c, x[ 6], S22, 0xc040b340); /* 18 */
GG (c, d, a, b, x[11], S23, 0x265e5a51); /* 19 */
GG (b, c, d, a, x[ 0], S24, 0xe9b6c7aa); /* 20 */
GG (a, b, c, d, x[ 5], S21, 0xd62f105d); /* 21 */
GG (d, a, b, c, x[10], S22, 0x2441453); /* 22 */
GG (c, d, a, b, x[15], S23, 0xd8a1e681); /* 23 */
GG (b, c, d, a, x[ 4], S24, 0xe7d3fbc8); /* 24 */
GG (a, b, c, d, x[ 9], S21, 0x21e1cde6); /* 25 */
GG (d, a, b, c, x[14], S22, 0xc33707d6); /* 26 */
GG (c, d, a, b, x[ 3], S23, 0xf4d50d87); /* 27 */
GG (b, c, d, a, x[ 8], S24, 0x455a14ed); /* 28 */
GG (a, b, c, d, x[13], S21, 0xa9e3e905); /* 29 */
GG (d, a, b, c, x[ 2], S22, 0xfcefa3f8); /* 30 */
GG (c, d, a, b, x[ 7], S23, 0x676f02d9); /* 31 */
GG (b, c, d, a, x[12], S24, 0x8d2a4c8a); /* 32 */
/* Round 3 */
HH (a, b, c, d, x[ 5], S31, 0xfffa3942); /* 33 */
HH (d, a, b, c, x[ 8], S32, 0x8771f681); /* 34 */
HH (c, d, a, b, x[11], S33, 0x6d9d6122); /* 35 */
HH (b, c, d, a, x[14], S34, 0xfde5380c); /* 36 */
HH (a, b, c, d, x[ 1], S31, 0xa4beea44); /* 37 */
HH (d, a, b, c, x[ 4], S32, 0x4bdecfa9); /* 38 */
HH (c, d, a, b, x[ 7], S33, 0xf6bb4b60); /* 39 */
HH (b, c, d, a, x[10], S34, 0xbebfbc70); /* 40 */
HH (a, b, c, d, x[13], S31, 0x289b7ec6); /* 41 */
HH (d, a, b, c, x[ 0], S32, 0xeaa127fa); /* 42 */
HH (c, d, a, b, x[ 3], S33, 0xd4ef3085); /* 43 */
HH (b, c, d, a, x[ 6], S34, 0x4881d05); /* 44 */
HH (a, b, c, d, x[ 9], S31, 0xd9d4d039); /* 45 */
HH (d, a, b, c, x[12], S32, 0xe6db99e5); /* 46 */
HH (c, d, a, b, x[15], S33, 0x1fa27cf8); /* 47 */
HH (b, c, d, a, x[ 2], S34, 0xc4ac5665); /* 48 */
/* Round 4 */
II (a, b, c, d, x[ 0], S41, 0xf4292244); /* 49 */
II (d, a, b, c, x[ 7], S42, 0x432aff97); /* 50 */
II (c, d, a, b, x[14], S43, 0xab9423a7); /* 51 */
II (b, c, d, a, x[ 5], S44, 0xfc93a039); /* 52 */
II (a, b, c, d, x[12], S41, 0x655b59c3); /* 53 */
II (d, a, b, c, x[ 3], S42, 0x8f0ccc92); /* 54 */
II (c, d, a, b, x[10], S43, 0xffeff47d); /* 55 */
II (b, c, d, a, x[ 1], S44, 0x85845dd1); /* 56 */
II (a, b, c, d, x[ 8], S41, 0x6fa87e4f); /* 57 */
II (d, a, b, c, x[15], S42, 0xfe2ce6e0); /* 58 */
II (c, d, a, b, x[ 6], S43, 0xa3014314); /* 59 */
II (b, c, d, a, x[13], S44, 0x4e0811a1); /* 60 */
II (a, b, c, d, x[ 4], S41, 0xf7537e82); /* 61 */
II (d, a, b, c, x[11], S42, 0xbd3af235); /* 62 */
II (c, d, a, b, x[ 2], S43, 0x2ad7d2bb); /* 63 */
II (b, c, d, a, x[ 9], S44, 0xeb86d391); /* 64 */
_state[0] += a;
_state[1] += b;
_state[2] += c;
_state[3] += d;
}
/* Encodes input (ulong) into output (byte). Assumes length is
a multiple of 4.
*/
void MD5::encode(const uint32* input, byte* output, size_t length) {
for (size_t i = 0, j = 0; j < length; ++i, j += 4) {
output[j]= (byte)(input[i] & 0xff);
output[j + 1] = (byte)((input[i] >> 8) & 0xff);
output[j + 2] = (byte)((input[i] >> 16) & 0xff);
output[j + 3] = (byte)((input[i] >> 24) & 0xff);
}
}
/* Decodes input (byte) into output (ulong). Assumes length is
a multiple of 4.
*/
void MD5::decode(const byte* input, uint32* output, size_t length) {
for (size_t i = 0, j = 0; j < length; ++i, j += 4) {
output[i] = ((uint32)input[j]) | (((uint32)input[j + 1]) << 8) |
(((uint32)input[j + 2]) << 16) | (((uint32)input[j + 3]) << 24);
}
}
/* Convert byte array to hex string. */
string MD5::bytesToHexString(const byte* input, size_t length) {
string str;
str.reserve(length << 1);
for (size_t i = 0; i < length; ++i) {
int t = input[i];
int a = t / 16;
int b = t % 16;
str.append(1, HEX[a]);
str.append(1, HEX[b]);
}
return str;
}
/* Convert digest to string value */
string MD5::toString() {
return bytesToHexString(digest(), 16);
}
❼ VS2013中c语言md5加密函数怎么调用
1、主要就是调用库函数，MD5加密说到底也是函数计算，没有什么思路的问题，了解md5的发明算法，本质是一个数学问题。
2、例程：
#ifndefMD5_H
#defineMD5_H
typedefstruct
{
unsignedintcount[2];
unsignedintstate[4];
unsignedcharbuffer[64];
}MD5_CTX;
#defineF(x,y,z)((x&y)|(~x&z))
#defineG(x,y,z)((x&z)|(y&~z))
#defineH(x,y,z)(x^y^z)
#defineI(x,y,z)(y^(x|~z))
#defineROTATE_LEFT(x,n)((x<<n)|(x>>(32-n)))
#defineFF(a,b,c,d,x,s,ac)
{
a+=F(b,c,d)+x+ac;
a=ROTATE_LEFT(a,s);
a+=b;
}
#defineGG(a,b,c,d,x,s,ac)
{
a+=G(b,c,d)+x+ac;
a=ROTATE_LEFT(a,s);
a+=b;
}
#defineHH(a,b,c,d,x,s,ac)
{
a+=H(b,c,d)+x+ac;
a=ROTATE_LEFT(a,s);
a+=b;
}
#defineII(a,b,c,d,x,s,ac)
{
a+=I(b,c,d)+x+ac;
a=ROTATE_LEFT(a,s);
a+=b;
}
voidMD5Init(MD5_CTX*context);
voidMD5Update(MD5_CTX*context,unsignedchar*input,unsignedintinputlen);
voidMD5Final(MD5_CTX*context,unsignedchardigest[16]);
voidMD5Transform(unsignedintstate[4],unsignedcharblock[64]);
voidMD5Encode(unsignedchar*output,unsignedint*input,unsignedintlen);
voidMD5Decode(unsignedint*output,unsignedchar*input,unsignedintlen);
#endif
源文件md5.c
#include<memory.h>
#include"md5.h"
unsignedcharPADDING[]={0x80,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
voidMD5Init(MD5_CTX*context)
{
context->count[0]=0;
context->count[1]=0;
context->state[0]=0x67452301;
context->state[1]=0xEFCDAB89;
context->state[2]=0x98BADCFE;
context->state[3]=0x10325476;
}
voidMD5Update(MD5_CTX*context,unsignedchar*input,unsignedintinputlen)
{
unsignedinti=0,index=0,partlen=0;
index=(context->count[0]>>3)&0x3F;
partlen=64-index;
context->count[0]+=inputlen<<3;
if(context->count[0]<(inputlen<<3))
context->count[1]++;
context->count[1]+=inputlen>>29;
if(inputlen>=partlen)
{
memcpy(&context->buffer[index],input,partlen);
MD5Transform(context->state,context->buffer);
for(i=partlen;i+64<=inputlen;i+=64)
MD5Transform(context->state,&input[i]);
index=0;
}
else
{
i=0;
}
memcpy(&context->buffer[index],&input[i],inputlen-i);
}
voidMD5Final(MD5_CTX*context,unsignedchardigest[16])
{
unsignedintindex=0,padlen=0;
unsignedcharbits[8];
index=(context->count[0]>>3)&0x3F;
padlen=(index<56)?(56-index):(120-index);
MD5Encode(bits,context->count,8);
MD5Update(context,PADDING,padlen);
MD5Update(context,bits,8);
MD5Encode(digest,context->state,16);
}
voidMD5Encode(unsignedchar*output,unsignedint*input,unsignedintlen)
{
unsignedinti=0,j=0;
while(j<len)
{
output[j]=input[i]&0xFF;
output[j+1]=(input[i]>>8)&0xFF;
output[j+2]=(input[i]>>16)&0xFF;
output[j+3]=(input[i]>>24)&0xFF;
i++;
j+=4;
}
}
voidMD5Decode(unsignedint*output,unsignedchar*input,unsignedintlen)
{
unsignedinti=0,j=0;
while(j<len)
{
output[i]=(input[j])|
(input[j+1]<<8)|
(input[j+2]<<16)|
(input[j+3]<<24);
i++;
j+=4;
}
}
voidMD5Transform(unsignedintstate[4],unsignedcharblock[64])
{
unsignedinta=state[0];
unsignedintb=state[1];
unsignedintc=state[2];
unsignedintd=state[3];
unsignedintx[64];
MD5Decode(x,block,64);
FF(a,b,c,d,x[0],7,0xd76aa478);/*1*/
FF(d,a,b,c,x[1],12,0xe8c7b756);/*2*/
FF(c,d,a,b,x[2],17,0x242070db);/*3*/
FF(b,c,d,a,x[3],22,0xc1bdceee);/*4*/
FF(a,b,c,d,x[4],7,0xf57c0faf);/*5*/
FF(d,a,b,c,x[5],12,0x4787c62a);/*6*/
FF(c,d,a,b,x[6],17,0xa8304613);/*7*/
FF(b,c,d,a,x[7],22,0xfd469501);/*8*/
FF(a,b,c,d,x[8],7,0x698098d8);/*9*/
FF(d,a,b,c,x[9],12,0x8b44f7af);/*10*/
FF(c,d,a,b,x[10],17,0xffff5bb1);/*11*/
FF(b,c,d,a,x[11],22,0x895cd7be);/*12*/
FF(a,b,c,d,x[12],7,0x6b901122);/*13*/
FF(d,a,b,c,x[13],12,0xfd987193);/*14*/
FF(c,d,a,b,x[14],17,0xa679438e);/*15*/
FF(b,c,d,a,x[15],22,0x49b40821);/*16*/
❽ 求一个简单的md5加密程序C或C++代码
C语言实现MD5算法
#include<stdio.h>
#define F(x, y, z) (((x) & (y)) | ((~x) & (z)))
#define G(x, y, z) (((x) & (z)) | ((y) & (~z)))
#define H(x, y, z) ((x) ^ (y) ^ (z))
#define I(x, y, z) ((y) ^ ((x) | (~z)))
#define RL(x, y) (((x) << (y)) | ((x) >> (32 - (y)))) //x向左循环移y位
#define PP(x) (x<<24)|((x<<8)&0xff0000)|((x>>8)&0xff00)|(x>>24) //将x高低位互换,例如PP(aabbccdd)=ddccbbaa
#define FF(a, b, c, d, x, s, ac) a = b + (RL((a + F(b,c,d) + x + ac),s))
#define GG(a, b, c, d, x, s, ac) a = b + (RL((a + G(b,c,d) + x + ac),s))
#define HH(a, b, c, d, x, s, ac) a = b + (RL((a + H(b,c,d) + x + ac),s))
#define II(a, b, c, d, x, s, ac) a = b + (RL((a + I(b,c,d) + x + ac),s))
unsigned A,B,C,D,a,b,c,d,i,len,flen[2],x[16]; //i临时变量,len文件长,flen[2]为64位二进制表示的文件初始长度
char filename[200]; //文件名
FILE *fp;
void md5(){ //MD5核心算法,供64轮
a=A,b=B,c=C,d=D;
/**//* Round 1 */
FF (a, b, c, d, x[ 0], 7, 0xd76aa478); /**//* 1 */
FF (d, a, b, c, x[ 1], 12, 0xe8c7b756); /**//* 2 */
FF (c, d, a, b, x[ 2], 17, 0x242070db); /**//* 3 */
FF (b, c, d, a, x[ 3], 22, 0xc1bdceee); /**//* 4 */
FF (a, b, c, d, x[ 4], 7, 0xf57c0faf); /**//* 5 */
FF (d, a, b, c, x[ 5], 12, 0x4787c62a); /**//* 6 */
FF (c, d, a, b, x[ 6], 17, 0xa8304613); /**//* 7 */
FF (b, c, d, a, x[ 7], 22, 0xfd469501); /**//* 8 */
FF (a, b, c, d, x[ 8], 7, 0x698098d8); /**//* 9 */
FF (d, a, b, c, x[ 9], 12, 0x8b44f7af); /**//* 10 */
FF (c, d, a, b, x[10], 17, 0xffff5bb1); /**//* 11 */
FF (b, c, d, a, x[11], 22, 0x895cd7be); /**//* 12 */
FF (a, b, c, d, x[12], 7, 0x6b901122); /**//* 13 */
FF (d, a, b, c, x[13], 12, 0xfd987193); /**//* 14 */
FF (c, d, a, b, x[14], 17, 0xa679438e); /**//* 15 */
FF (b, c, d, a, x[15], 22, 0x49b40821); /**//* 16 */
/**//* Round 2 */
GG (a, b, c, d, x[ 1], 5, 0xf61e2562); /**//* 17 */
GG (d, a, b, c, x[ 6], 9, 0xc040b340); /**//* 18 */
GG (c, d, a, b, x[11], 14, 0x265e5a51); /**//* 19 */
GG (b, c, d, a, x[ 0], 20, 0xe9b6c7aa); /**//* 20 */
GG (a, b, c, d, x[ 5], 5, 0xd62f105d); /**//* 21 */
GG (d, a, b, c, x[10], 9, 0x02441453); /**//* 22 */
GG (c, d, a, b, x[15], 14, 0xd8a1e681); /**//* 23 */
GG (b, c, d, a, x[ 4], 20, 0xe7d3fbc8); /**//* 24 */
GG (a, b, c, d, x[ 9], 5, 0x21e1cde6); /**//* 25 */
GG (d, a, b, c, x[14], 9, 0xc33707d6); /**//* 26 */
GG (c, d, a, b, x[ 3], 14, 0xf4d50d87); /**//* 27 */
GG (b, c, d, a, x[ 8], 20, 0x455a14ed); /**//* 28 */
GG (a, b, c, d, x[13], 5, 0xa9e3e905); /**//* 29 */
GG (d, a, b, c, x[ 2], 9, 0xfcefa3f8); /**//* 30 */
GG (c, d, a, b, x[ 7], 14, 0x676f02d9); /**//* 31 */
GG (b, c, d, a, x[12], 20, 0x8d2a4c8a); /**//* 32 */
/**//* Round 3 */
HH (a, b, c, d, x[ 5], 4, 0xfffa3942); /**//* 33 */
HH (d, a, b, c, x[ 8], 11, 0x8771f681); /**//* 34 */
HH (c, d, a, b, x[11], 16, 0x6d9d6122); /**//* 35 */
HH (b, c, d, a, x[14], 23, 0xfde5380c); /**//* 36 */
HH (a, b, c, d, x[ 1], 4, 0xa4beea44); /**//* 37 */
HH (d, a, b, c, x[ 4], 11, 0x4bdecfa9); /**//* 38 */
HH (c, d, a, b, x[ 7], 16, 0xf6bb4b60); /**//* 39 */
HH (b, c, d, a, x[10], 23, 0xbebfbc70); /**//* 40 */
HH (a, b, c, d, x[13], 4, 0x289b7ec6); /**//* 41 */
HH (d, a, b, c, x[ 0], 11, 0xeaa127fa); /**//* 42 */
HH (c, d, a, b, x[ 3], 16, 0xd4ef3085); /**//* 43 */
HH (b, c, d, a, x[ 6], 23, 0x04881d05); /**//* 44 */
HH (a, b, c, d, x[ 9], 4, 0xd9d4d039); /**//* 45 */
HH (d, a, b, c, x[12], 11, 0xe6db99e5); /**//* 46 */
HH (c, d, a, b, x[15], 16, 0x1fa27cf8); /**//* 47 */
HH (b, c, d, a, x[ 2], 23, 0xc4ac5665); /**//* 48 */
/**//* Round 4 */
II (a, b, c, d, x[ 0], 6, 0xf4292244); /**//* 49 */
II (d, a, b, c, x[ 7], 10, 0x432aff97); /**//* 50 */
II (c, d, a, b, x[14], 15, 0xab9423a7); /**//* 51 */
II (b, c, d, a, x[ 5], 21, 0xfc93a039); /**//* 52 */
II (a, b, c, d, x[12], 6, 0x655b59c3); /**//* 53 */
II (d, a, b, c, x[ 3], 10, 0x8f0ccc92); /**//* 54 */
II (c, d, a, b, x[10], 15, 0xffeff47d); /**//* 55 */
II (b, c, d, a, x[ 1], 21, 0x85845dd1); /**//* 56 */
II (a, b, c, d, x[ 8], 6, 0x6fa87e4f); /**//* 57 */
II (d, a, b, c, x[15], 10, 0xfe2ce6e0); /**//* 58 */
II (c, d, a, b, x[ 6], 15, 0xa3014314); /**//* 59 */
II (b, c, d, a, x[13], 21, 0x4e0811a1); /**//* 60 */
II (a, b, c, d, x[ 4], 6, 0xf7537e82); /**//* 61 */
II (d, a, b, c, x[11], 10, 0xbd3af235); /**//* 62 */
II (c, d, a, b, x[ 2], 15, 0x2ad7d2bb); /**//* 63 */
II (b, c, d, a, x[ 9], 21, 0xeb86d391); /**//* 64 */
A += a;
B += b;
C += c;
D += d;
}
main(){
while(1){
printf("Input file:");
gets(filename); //用get函数,避免scanf以空格分割数据,
if (filename[0]==34) filename[strlen(filename)-1]=0,strcpy(filename,filename+1); //支持文件拖曳,但会多出双引号,这里是处理多余的双引号
if (!strcmp(filename,"exit")) exit(0); //输入exit退出
if (!(fp=fopen(filename,"rb"))) {printf("Can not open this file!\n");continue;} //以二进制打开文件
fseek(fp, 0, SEEK_END); //文件指针转到文件末尾
if((len=ftell(fp))==-1) {printf("Sorry! Can not calculate files which larger than 2 GB!\n");fclose(fp);continue;} //ftell函数返回long,最大为2GB,超出返回-1
rewind(fp); //文件指针复位到文件头
A=0x67452301,B=0xefcdab89,C=0x98badcfe,D=0x10325476; //初始化链接变量
flen[1]=len/0x20000000; //flen单位是bit
flen[0]=(len%0x20000000)*8;
memset(x,0,64); //初始化x数组为0
fread(&x,4,16,fp); //以4字节为一组,读取16组数据
for(i=0;i<len/64;i++){ //循环运算直至文件结束
md5();
memset(x,0,64);
fread(&x,4,16,fp);
}
((char*)x)[len%64]=128; //文件结束补1,补0操作,128二进制即10000000
if(len%64>55) md5(),memset(x,0,64);
memcpy(x+14,flen,8); //文件末尾加入原文件的bit长度
md5();
fclose(fp);
printf("MD5 Code:%08x%08x%08x%08x\n",PP(A),PP(B),PP(C),PP(D)); //高低位逆反输出
}
}
❾ C语言实现文件传输时用md5加密
搜一下：C语言实现文件传输时用md5加密