基本算法-MD5

一，描述

       MD5报文摘要生成算法在数据安全和通信领域有着广泛的应用，最早应用于信息传输过程中防止数据被中间修改，一直到现在的存储领域做为文件的指纹来实现一些更加复杂的功能，比如视频网站，新视频上传的时候会生成一个视频对应的MD5指纹，后继再有同样的视频上传的时候通过md5指纹就可以判断当前上传的视频是否已经被上传过，通过这种办法即可实现秒传视频。

二，库

     linux的openssl 库中有大量的安全相关算法的实现，md5就是其中一个。

    其头文件如下：

   

/* crypto/md5/md5.h *//* Copyright (C) 1995-1998 Eric Young ([e-mail]) * All rights reserved. * * This package is an SSL implementation written * by Eric Young ([e-mail]). * The implementation was written so as to conform with Netscapes SSL. *  * This library is free for commercial and non-commercial use as long as * the following conditions are aheared to.  The following conditions * apply to all code found in this distribution, be it the RC4, RSA, * lhash, DES, etc., code; not just the SSL code.  The SSL documentation * included with this distribution is covered by the same copyright terms * except that the holder is Tim Hudson ([e-mail]). *  * Copyright remains Eric Young's, and as such any Copyright notices in * the code are not to be removed. * If this package is used in a product, Eric Young should be given attribution * as the author of the parts of the library used. * This can be in the form of a textual message at program startup or * in documentation (online or textual) provided with the package. *  * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the copyright *    notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright *    notice, this list of conditions and the following disclaimer in the *    documentation and/or other materials provided with the distribution. * 3. All advertising materials mentioning features or use of this software *    must display the following acknowledgement: *    "This product includes cryptographic software written by *     Eric Young ([e-mail])" *    The word 'cryptographic' can be left out if the rouines from the library *    being used are not cryptographic related :-). * 4. If you include any Windows specific code (or a derivative thereof) from  *    the apps directory (application code) you must include an acknowledgement: *    "This product includes software written by Tim Hudson ([e-mail])" *  * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. *  * The licence and distribution terms for any publically available version or * derivative of this code cannot be changed.  i.e. this code cannot simply be * copied and put under another distribution licence * [including the GNU Public Licence.] */#ifndef HEADER_MD5_H#define HEADER_MD5_H#include <openssl/e_os2.h>#include <stddef.h>#ifdef  __cplusplusextern "C" {#endif#ifdef OPENSSL_NO_MD5#error MD5 is disabled.#endif/* * !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! * ! MD5_LONG has to be at least 32 bits wide. If it's wider, then ! * ! MD5_LONG_LOG2 has to be defined along.   ! * !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! */#if defined(__LP32__)#define MD5_LONG unsigned long#elif defined(OPENSSL_SYS_CRAY) || defined(__ILP64__)#define MD5_LONG unsigned long#define MD5_LONG_LOG2 3/* * _CRAY note. I could declare short, but I have no idea what impact * does it have on performance on none-T3E machines. I could declare * int, but at least on C90 sizeof(int) can be chosen at compile time. * So I've chosen long... *<[e-mail]> */#else#define MD5_LONG unsigned int#endif#define MD5_CBLOCK64#define MD5_LBLOCK(MD5_CBLOCK/4)#define MD5_DIGEST_LENGTH 16typedef struct MD5state_st{MD5_LONG A,B,C,D;MD5_LONG Nl,Nh;MD5_LONG data[MD5_LBLOCK];unsigned int num;} MD5_CTX;#ifdef OPENSSL_FIPSint private_MD5_Init(MD5_CTX *c);#endifint MD5_Init(MD5_CTX *c);int MD5_Update(MD5_CTX *c, const void *data, size_t len);int MD5_Final(unsigned char *md, MD5_CTX *c);unsigned char *MD5(const unsigned char *d, size_t n, unsigned char *md);void MD5_Transform(MD5_CTX *c, const unsigned char *b);#ifdef  __cplusplus}#endif#endif

 

三，源码

   

/*************************************************************************    > File Name: md5.cpp    > Author:zhangtx    > Mail: [e-mail]     > Created Time: 2015年06月27日 星期六 11时10分08秒 ************************************************************************/#include<iostream>#include <openssl/md5.h>#include <string>#include <string.h>#include <stdio.h>#include <stdlib.h>using namespace std;int genMd5Value(const char * src,unsigned char *res){    MD5_CTX ctx;    MD5_Init(&ctx);    MD5_Update(&ctx,src,strlen(src));    MD5_Final(res,&ctx);    return 0;}void printResult(unsigned char *value){    printf("md5:");    for(int idx=0;idx<MD5_DIGEST_LENGTH;idx++)    {        printf("%02x",value[idx]);    }    printf("\n");}int main(int argc,char *argv[]){    char src[]="1ds,mmnewlk3fk3fk;q1k;fkmam21'3jr2ji3r2wflkdm'\n";    unsigned char res[MD5_DIGEST_LENGTH];    genMd5Value(src,res);    printf("raw:%s",src);    printResult(res);    return 0;}

 

四，结果

[root@M-192-168-10-225 lab]# g++ md5.cpp -lssl -g[root@M-192-168-10-225 lab]# ./a.outraw:1ds,mmnewlk3fk3fk;q1k;fkmam21'3jr2ji3r2wflkdm'md5:2a2e00dc44420b1fa9cade74bcbe237f[root@M-192-168-10-225 lab]# openssl md5 abc.conf MD5(abc.conf)= 2a2e00dc44420b1fa9cade74bcbe237f