base8 mp

base8

int __cdecl sub_4117A0(char *a1, _BYTE *a2)
{
  int result; // eax
  char v3[16]; // [esp+DCh] [ebp-14h] BYREF

  __CheckForDebuggerJustMyCode(&unk_41C014);
  strcpy(v3, "01234567");
  *a2 = v3[*a1 >> 5];
  a2[1] = v3[(*a1 >> 2) & 7];
  a2[2] = v3[2 * (*a1 & 3) + (a1[1] >> 7)];
  a2[3] = v3[(a1[1] >> 4) & 7];
  a2[4] = v3[(a1[1] >> 1) & 7];
  a2[5] = v3[4 * (a1[1] & 1) + (a1[2] >> 6)];
  a2[6] = v3[(a1[2] >> 3) & 7];
  result = 7;
  a2[7] = v3[a1[2] & 7];
  return result;
}

此处为base8形式可以用大数运算来进行

具体解密代码如下‘

char zidian[]="01234567";
int flag=0;
char jiemizifu[3];
int bianli(char a)
{
    int j=0;
        for(int b=0;b<8;b++)
        {
            if(a==zidian[b])
            {
                return b;
            }
        }
}
long long int zhuanhua10(char *a,char *b)
{
if(b-a>7)
return 0;
return bianli(*a)+zhuanhua10(a-1,b)*8;
}
long long int zhuanhua256(long long int a)
{
if(a<=0)
return 0;
return a%256+zhuanhua256((a-a%256)/256)*1000;
}
void jiemi(char *a,char *b,int lenth)
{
for(int i=0,j=0;j<lenth;i+=3,j+=8)
{
    long long int linshi=zhuanhua256(zhuanhua10(a+j+7,a+j+7));
    (b)[i+2]=linshi%1000;
    linshi/=1000;
    (b)[i+1]=(linshi%1000);
    linshi/=1000;
    (b)[i]=(linshi%1000);
}
}
int main()
{
char zifuchuan[]="2645153225431064252551072025110716055127160331032465113222654061142345302363050424443400";
char a[100];
jiemi(zifuchuan,(a),89);
printf("%s",a);
}