linux MD5使用

# define MD5_LONG unsigned int

# define MD5_CBLOCK      64
# define MD5_LBLOCK      (MD5_CBLOCK/4)
# define MD5_DIGEST_LENGTH 16

typedef struct MD5state_st {
    MD5_LONG A, B, C, D;
    MD5_LONG Nl, Nh;
    MD5_LONG data[MD5_LBLOCK];
    unsigned int num;
} MD5_CTX;

int 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);

举例

#include "openssl/md5.h"

int i = 0;
char *data = "hello";
unsigned char md[MD5_DIGEST_LENGTH] = {0};
MD5_CTX c;

MD5_Init(&c);
MD5_Update(&c, data, strlen(data));
MD5_Final(md, &c);

//MD5(data, strlen(data), md);	//二选一

for(i = 0; i < MD5_DIGEST_LENGTH; i++)
{
	printf("0x%02x ", md[i]);
}
printf("\n");

# gcc md5.c -lcrypto
# ./a.out             
0x5d 0x41 0x40 0x2a 0xbc 0x4b 0x2a 0x76 0xb9 0x71 0x9d 0x91 0x10 0x17 0xc5 0x92 

md5sum
用于生成和校验文件的md5值

-b：以二进制模式读入文件内容
-t：以文本模式读入文件内容
-c：根据已生成的md5值，对现存文件进行校验