在Access数据库中,为了安全起见,可以为所建的数据库设置 密码 。但是, 密码 忘了怎么办?别急,这里介绍一种 找回 密码 的方法。 用Access所建的数据库,在库文件的地址00000042处开始的13个字节是Access库的 密码 位。如果一个未加密的库,这13个字节原始
在Access数据库中,为了安全起见,可以为所建的数据库设置密码。但是,密码忘了怎么办?别急,这里介绍一种找回密码的方法。用Access所建的数据库,在库文件的地址00000042处开始的13个字节是Access库的密码位。如果一个未加密的库,这13个字节原始数据依次为:86 FB 37 5D 44 9C FA C6 28 E6 13。事实上,当你设置了密码后,Access就将你的密码(请注意你所输入的密码是本文字符)的ACSII码与以上的13个字节数据进行异或操作,因此,从库文件的地址00000042开始的13个字节就变成了密钥了。例如,如果你设置的密码为abc,经过异或操作后,则从00000042处开始的13个字节的数据变成了E7 99 8F 37 5D 44 9C FA C6 28 E6 13。一个数据经过一次异或操作后,再一次经过同样的异或操作就可还原了。因此,对已经设置了密码的Access库,只要将13个密钥数据与原始的13个数据进行一次异或操作就可得到密码了。
以下是一个C语言的破解程序:
/*假设加密后的Access库为myacc.mdb,并存放在C盘的根目录下*/
#include ″stdio.h″
main()
{FILE * fp
char mm0[13]={0x86,0xfb,0xec,0x37,0x5d,0x44,0x9c,0xfa,0xc6,0x5e,0x28,0xe6,0x13};
/*这是13个原始数据*/
char mml[13],mm2[13];
/*mm1用来存放加密后的13个密钥;mm2用来存放密码*/
int i,k;
fp=fopen(″c:\\myacc.mdb″,″rb″);
if(fp=NULL){
printf(″\n不能打开该库!″);
exit(0);}
rewind(fp);fseek(fp,0x42L,0);
fread(mm1,13,1,fp);/*读取密钥*/
for(i=0;i
mm2[i]=mm0[i]^mm[i];*/原始数据与密钥异或*/
else
break;}
k=1;fclose(fp);
if(k=0)
printf(″未设密码!″);
else{printf(″\n密码是:\n″);
for(i=0;ibr>
printf(″%c,mm2[i]″);}}
顺便提一句,Access库设置密码时,虽然允许输入最多14个密码字符,但只有前13个有效。

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