IDA打开后核心代码如下：
int __cdecl main(int argc, const char **argv, const char **envp)
{
int v4; // [rsp+20h] [rbp-60h]
int v5; // [rsp+24h] [rbp-5Ch]
int v6; // [rsp+28h] [rbp-58h]
int v7; // [rsp+2Ch] [rbp-54h]
int v8; // [rsp+30h] [rbp-50h]
int v9; // [rsp+34h] [rbp-4Ch]
int v10; // [rsp+38h] [rbp-48h]
int v11; // [rsp+3Ch] [rbp-44h]
int v12; // [rsp+40h] [rbp-40h]
int v13; // [rsp+44h] [rbp-3Ch]
int v14; // [rsp+48h] [rbp-38h]
int v15; // [rsp+4Ch] [rbp-34h]
int v16; // [rsp+50h] [rbp-30h]
int v17; // [rsp+54h] [rbp-2Ch]
int v18; // [rsp+58h] [rbp-28h]
int v19; // [rsp+5Ch] [rbp-24h]
int v20; // [rsp+60h] [rbp-20h]
int v21; // [rsp+64h] [rbp-1Ch]
int v22; // [rsp+68h] [rbp-18h]
int v23; // [rsp+6Ch] [rbp-14h]
int v24; // [rsp+70h] [rbp-10h]
int v25; // [rsp+74h] [rbp-Ch]
int v26; // [rsp+78h] [rbp-8h]
int v27; // [rsp+7Ch] [rbp-4h]
int v28; // [rsp+80h] [rbp+0h]
int v29; // [rsp+84h] [rbp+4h]
int v30; // [rsp+88h] [rbp+8h]
int v31; // [rsp+8Ch] [rbp+Ch]
int v32; // [rsp+90h] [rbp+10h]
int v33; // [rsp+94h] [rbp+14h]
int v34; // [rsp+98h] [rbp+18h]
int v35; // [rsp+9Ch] [rbp+1Ch]
int v36; // [rsp+A0h] [rbp+20h]
int v37; // [rsp+A4h] [rbp+24h]
int v38; // [rsp+A8h] [rbp+28h]
int v39; // [rsp+ACh] [rbp+2Ch]
int v40; // [rsp+B0h] [rbp+30h]
int v41; // [rsp+B4h] [rbp+34h]
int v42; // [rsp+B8h] [rbp+38h]
int v43; // [rsp+BCh] [rbp+3Ch]
int v44; // [rsp+C0h] [rbp+40h]
int v45; // [rsp+C4h] [rbp+44h]
unsigned __int8 v46; // [rsp+D0h] [rbp+50h]
unsigned __int8 v47; // [rsp+D1h] [rbp+51h]
unsigned __int8 v48; // [rsp+D2h] [rbp+52h]
unsigned __int8 v49; // [rsp+D3h] [rbp+53h]
unsigned __int8 v50; // [rsp+D4h] [rbp+54h]
unsigned __int8 v51; // [rsp+D5h] [rbp+55h]
unsigned __int8 v52; // [rsp+D6h] [rbp+56h]
unsigned __int8 v53; // [rsp+D7h] [rbp+57h]
unsigned __int8 v54; // [rsp+D8h] [rbp+58h]
unsigned __int8 v55; // [rsp+D9h] [rbp+59h]
unsigned __int8 v56; // [rsp+DAh] [rbp+5Ah]
unsigned __int8 v57; // [rsp+DBh] [rbp+5Bh]
unsigned __int8 v58; // [rsp+DCh] [rbp+5Ch]
unsigned __int8 v59; // [rsp+DDh] [rbp+5Dh]
unsigned __int8 v60; // [rsp+DEh] [rbp+5Eh]
unsigned __int8 v61; // [rsp+DFh] [rbp+5Fh]
unsigned __int8 v62; // [rsp+E0h] [rbp+60h]
unsigned __int8 v63; // [rsp+E1h] [rbp+61h]
unsigned __int8 v64; // [rsp+E2h] [rbp+62h]
unsigned __int8 v65; // [rsp+E3h] [rbp+63h]
unsigned __int8 v66; // [rsp+E4h] [rbp+64h]
unsigned __int8 v67; // [rsp+E5h] [rbp+65h]
unsigned __int8 v68; // [rsp+E6h] [rbp+66h]
unsigned __int8 v69; // [rsp+E7h] [rbp+67h]
unsigned __int8 v70; // [rsp+E8h] [rbp+68h]
unsigned __int8 v71; // [rsp+E9h] [rbp+69h]
unsigned __int8 v72; // [rsp+EAh] [rbp+6Ah]
unsigned __int8 v73; // [rsp+EBh] [rbp+6Bh]
unsigned __int8 v74; // [rsp+ECh] [rbp+6Ch]
unsigned __int8 v75; // [rsp+EDh] [rbp+6Dh]
unsigned __int8 v76; // [rsp+EEh] [rbp+6Eh]
unsigned __int8 v77; // [rsp+EFh] [rbp+6Fh]
unsigned __int8 v78; // [rsp+F0h] [rbp+70h]
unsigned __int8 v79; // [rsp+F1h] [rbp+71h]
unsigned __int8 v80; // [rsp+F2h] [rbp+72h]
unsigned __int8 v81; // [rsp+F3h] [rbp+73h]
unsigned __int8 v82; // [rsp+F4h] [rbp+74h]
unsigned __int8 v83; // [rsp+F5h] [rbp+75h]
unsigned __int8 v84; // [rsp+F6h] [rbp+76h]
unsigned __int8 v85; // [rsp+F7h] [rbp+77h]
unsigned __int8 v86; // [rsp+F8h] [rbp+78h]
unsigned __int8 v87; // [rsp+F9h] [rbp+79h]
int Dst[43]; // [rsp+110h] [rbp+90h]
int i; // [rsp+1BCh] [rbp+13Ch]
_main(*(_QWORD *)&argc, argv, envp);
memcpy(Dst, &unk_404020, 0xA8ui64);
printf("plz input your flag:");
scanf("%42s", &v46);
v4 = 34 * v49 + 12 * v46 + 53 * v47 + 6 * v48 + 58 * v50 + 36 * v51 + v52;
v5 = 27 * v50 + 73 * v49 + 12 * v48 + 83 * v46 + 85 * v47 + 96 * v51 + 52 * v52;
v6 = 24 * v48 + 78 * v46 + 53 * v47 + 36 * v49 + 86 * v50 + 25 * v51 + 46 * v52;
v7 = 78 * v47 + 39 * v46 + 52 * v48 + 9 * v49 + 62 * v50 + 37 * v51 + 84 * v52;
v8 = 48 * v50 + 14 * v48 + 23 * v46 + 6 * v47 + 74 * v49 + 12 * v51 + 83 * v52;
v9 = 15 * v51 + 48 * v50 + 92 * v48 + 85 * v47 + 27 * v46 + 42 * v49 + 72 * v52;
v10 = 26 * v51 + 67 * v49 + 6 * v47 + 4 * v46 + 3 * v48 + 68 * v52;
v11 = 34 * v56 + 12 * v53 + 53 * v54 + 6 * v55 + 58 * v57 + 36 * v58 + v59;
v12 = 27 * v57 + 73 * v56 + 12 * v55 + 83 * v53 + 85 * v54 + 96 * v58 + 52 * v59;
v13 = 24 * v55 + 78 * v53 + 53 * v54 + 36 * v56 + 86 * v57 + 25 * v58 + 46 * v59;
v14 = 78 * v54 + 39 * v53 + 52 * v55 + 9 * v56 + 62 * v57 + 37 * v58 + 84 * v59;
v15 = 48 * v57 + 14 * v55 + 23 * v53 + 6 * v54 + 74 * v56 + 12 * v58 + 83 * v59;
v16 = 15 * v58 + 48 * v57 + 92 * v55 + 85 * v54 + 27 * v53 + 42 * v56 + 72 * v59;
v17 = 26 * v58 + 67 * v56 + 6 * v54 + 4 * v53 + 3 * v55 + 68 * v59;
v18 = 34 * v63 + 12 * v60 + 53 * v61 + 6 * v62 + 58 * v64 + 36 * v65 + v66;
v19 = 27 * v64 + 73 * v63 + 12 * v62 + 83 * v60 + 85 * v61 + 96 * v65 + 52 * v66;
v20 = 24 * v62 + 78 * v60 + 53 * v61 + 36 * v63 + 86 * v64 + 25 * v65 + 46 * v66;
v21 = 78 * v61 + 39 * v60 + 52 * v62 + 9 * v63 + 62 * v64 + 37 * v65 + 84 * v66;
v22 = 48 * v64 + 14 * v62 + 23 * v60 + 6 * v61 + 74 * v63 + 12 * v65 + 83 * v66;
v23 = 15 * v65 + 48 * v64 + 92 * v62 + 85 * v61 + 27 * v60 + 42 * v63 + 72 * v66;
v24 = 26 * v65 + 67 * v63 + 6 * v61 + 4 * v60 + 3 * v62 + 68 * v66;
v25 = 34 * v70 + 12 * v67 + 53 * v68 + 6 * v69 + 58 * v71 + 36 * v72 + v73;
v26 = 27 * v71 + 73 * v70 + 12 * v69 + 83 * v67 + 85 * v68 + 96 * v72 + 52 * v73;
v27 = 24 * v69 + 78 * v67 + 53 * v68 + 36 * v70 + 86 * v71 + 25 * v72 + 46 * v73;
v28 = 78 * v68 + 39 * v67 + 52 * v69 + 9 * v70 + 62 * v71 + 37 * v72 + 84 * v73;
v29 = 48 * v71 + 14 * v69 + 23 * v67 + 6 * v68 + 74 * v70 + 12 * v72 + 83 * v73;
v30 = 15 * v72 + 48 * v71 + 92 * v69 + 85 * v68 + 27 * v67 + 42 * v70 + 72 * v73;
v31 = 26 * v72 + 67 * v70 + 6 * v68 + 4 * v67 + 3 * v69 + 68 * v73;
v32 = 34 * v77 + 12 * v74 + 53 * v75 + 6 * v76 + 58 * v78 + 36 * v79 + v80;
v33 = 27 * v78 + 73 * v77 + 12 * v76 + 83 * v74 + 85 * v75 + 96 * v79 + 52 * v80;
v34 = 24 * v76 + 78 * v74 + 53 * v75 + 36 * v77 + 86 * v78 + 25 * v79 + 46 * v80;
v35 = 78 * v75 + 39 * v74 + 52 * v76 + 9 * v77 + 62 * v78 + 37 * v79 + 84 * v80;
v36 = 48 * v78 + 14 * v76 + 23 * v74 + 6 * v75 + 74 * v77 + 12 * v79 + 83 * v80;
v37 = 15 * v79 + 48 * v78 + 92 * v76 + 85 * v75 + 27 * v74 + 42 * v77 + 72 * v80;
v38 = 26 * v79 + 67 * v77 + 6 * v75 + 4 * v74 + 3 * v76 + 68 * v80;
v39 = 34 * v84 + 12 * v81 + 53 * v82 + 6 * v83 + 58 * v85 + 36 * v86 + v87;
v40 = 27 * v85 + 73 * v84 + 12 * v83 + 83 * v81 + 85 * v82 + 96 * v86 + 52 * v87;
v41 = 24 * v83 + 78 * v81 + 53 * v82 + 36 * v84 + 86 * v85 + 25 * v86 + 46 * v87;
v42 = 78 * v82 + 39 * v81 + 52 * v83 + 9 * v84 + 62 * v85 + 37 * v86 + 84 * v87;
v43 = 48 * v85 + 14 * v83 + 23 * v81 + 6 * v82 + 74 * v84 + 12 * v86 + 83 * v87;
v44 = 15 * v86 + 48 * v85 + 92 * v83 + 85 * v82 + 27 * v81 + 42 * v84 + 72 * v87;
v45 = 26 * v86 + 67 * v84 + 6 * v82 + 4 * v81 + 3 * v83 + 68 * v87;
for ( i = 0; i <= 41; ++i )
{
if ( *(&v4 + i) != Dst[i] )
{
printf("error");
exit(0);
}
}
printf("win");
return 0;
}
看着十分凌乱，我们整理一下代码
int __cdecl main(int argc, const char **argv, const char **envp)
{
int cyphered[42]; // [rsp+20h] [rbp-60h]
char input_str[42]; // [rsp+D0h] [rbp+50h]
int Dst[43]; // [rsp+110h] [rbp+90h]
int i; // [rsp+1BCh] [rbp+13Ch]
_main(*(_QWORD *)&argc, argv, envp);
memcpy(Dst, &unk_404020, 0xA8ui64);
printf("plz input your flag:");
scanf("%42s", input_str);
cyphered[0] = 34 * (unsigned __int8)input_str[3]
+ 12 * (unsigned __int8)input_str[0]
+ 53 * (unsigned __int8)input_str[1]
+ 6 * (unsigned __int8)input_str[2]
+ 58 * (unsigned __int8)input_str[4]
+ 36 * (unsigned __int8)input_str[5]
+ (unsigned __int8)input_str[6];
cyphered[1] = 27 * (unsigned __int8)input_str[4]
+ 73 * (unsigned __int8)input_str[3]
+ 12 * (unsigned __int8)input_str[2]
+ 83 * (unsigned __int8)input_str[0]
+ 85 * (unsigned __int8)input_str[1]
+ 96 * (unsigned __int8)input_str[5]
+ 52 * (unsigned __int8)input_str[6];
cyphered[2] = 24 * (unsigned __int8)input_str[2]
+ 78 * (unsigned __int8)input_str[0]
+ 53 * (unsigned __int8)input_str[1]
+ 36 * (unsigned __int8)input_str[3]
+ 86 * (unsigned __int8)input_str[4]
+ 25 * (unsigned __int8)input_str[5]
+ 46 * (unsigned __int8)input_str[6];
cyphered[3] = 78 * (unsigned __int8)input_str[1]
+ 39 * (unsigned __int8)input_str[0]
+ 52 * (unsigned __int8)input_str[2]
+ 9 * (unsigned __int8)input_str[3]
+ 62 * (unsigned __int8)input_str[4]
+ 37 * (unsigned __int8)input_str[5]
+ 84 * (unsigned __int8)input_str[6];
cyphered[4] = 48 * (unsigned __int8)input_str[4]
+ 14 * (unsigned __int8)input_str[2]
+ 23 * (unsigned __int8)input_str[0]
+ 6 * (unsigned __int8)input_str[1]
+ 74 * (unsigned __int8)input_str[3]
+ 12 * (unsigned __int8)input_str[5]
+ 83 * (unsigned __int8)input_str[6];
cyphered[5] = 15 * (unsigned __int8)input_str[5]
+ 48 * (unsigned __int8)input_str[4]
+ 92 * (unsigned __int8)input_str[2]
+ 85 * (unsigned __int8)input_str[1]
+ 27 * (unsigned __int8)input_str[0]
+ 42 * (unsigned __int8)input_str[3]
+ 72 * (unsigned __int8)input_str[6];
cyphered[6] = 26 * (unsigned __int8)input_str[5]
+ 67 * (unsigned __int8)input_str[3]
+ 6 * (unsigned __int8)input_str[1]
+ 4 * (unsigned __int8)input_str[0]
+ 3 * (unsigned __int8)input_str[2]
+ 68 * (unsigned __int8)input_str[6];
cyphered[7] = 34 * (unsigned __int8)input_str[10]
+ 12 * (unsigned __int8)input_str[7]
+ 53 * (unsigned __int8)input_str[8]
+ 6 * (unsigned __int8)input_str[9]
+ 58 * (unsigned __int8)input_str[11]
+ 36 * (unsigned __int8)input_str[12]
+ (unsigned __int8)input_str[13];
cyphered[8] = 27 * (unsigned __int8)input_str[11]
+ 73 * (unsigned __int8)input_str[10]
+ 12 * (unsigned __int8)input_str[9]
+ 83 * (unsigned __int8)input_str[7]
+ 85 * (unsigned __int8)input_str[8]
+ 96 * (unsigned __int8)input_str[12]
+ 52 * (unsigned __int8)input_str[13];
cyphered[9] = 24 * (unsigned __int8)input_str[9]
+ 78 * (unsigned __int8)input_str[7]
+ 53 * (unsigned __int8)input_str[8]
+ 36 * (unsigned __int8)input_str[10]
+ 86 * (unsigned __int8)input_str[11]
+ 25 * (unsigned __int8)input_str[12]
+ 46 * (unsigned __int8)input_str[13];
cyphered[10] = 78 * (unsigned __int8)input_str[8]
+ 39 * (unsigned __int8)input_str[7]
+ 52 * (unsigned __int8)input_str[9]
+ 9 * (unsigned __int8)input_str[10]
+ 62 * (unsigned __int8)input_str[11]
+ 37 * (unsigned __int8)input_str[12]
+ 84 * (unsigned __int8)input_str[13];
cyphered[11] = 48 * (unsigned __int8)input_str[11]
+ 14 * (unsigned __int8)input_str[9]
+ 23 * (unsigned __int8)input_str[7]
+ 6 * (unsigned __int8)input_str[8]
+ 74 * (unsigned __int8)input_str[10]
+ 12 * (unsigned __int8)input_str[12]
+ 83 * (unsigned __int8)input_str[13];
cyphered[12] = 15 * (unsigned __int8)input_str[12]
+ 48 * (unsigned __int8)input_str[11]
+ 92 * (unsigned __int8)input_str[9]
+ 85 * (unsigned __int8)input_str[8]
+ 27 * (unsigned __int8)input_str[7]
+ 42 * (unsigned __int8)input_str[10]
+ 72 * (unsigned __int8)input_str[13];
cyphered[13] = 26 * (unsigned __int8)input_str[12]
+ 67 * (unsigned __int8)input_str[10]
+ 6 * (unsigned __int8)input_str[8]
+ 4 * (unsigned __int8)input_str[7]
+ 3 * (unsigned __int8)input_str[9]
+ 68 * (unsigned __int8)input_str[13];
cyphered[14] = 34 * (unsigned __int8)input_str[17]
+ 12 * (unsigned __int8)input_str[14]
+ 53 * (unsigned __int8)input_str[15]
+ 6 * (unsigned __int8)input_str[16]
+ 58 * (unsigned __int8)input_str[18]
+ 36 * (unsigned __int8)input_str[19]
+ (unsigned __int8)input_str[20];
cyphered[15] = 27 * (unsigned __int8)input_str[18]
+ 73 * (unsigned __int8)input_str[17]
+ 12 * (unsigned __int8)input_str[16]
+ 83 * (unsigned __int8)input_str[14]
+ 85 * (unsigned __int8)input_str[15]
+ 96 * (unsigned __int8)input_str[19]
+ 52 * (unsigned __int8)input_str[20];
cyphered[16] = 24 * (unsigned __int8)input_str[16]
+ 78 * (unsigned __int8)input_str[14]
+ 53 * (unsigned __int8)input_str[15]
+ 36 * (unsigned __int8)input_str[17]
+ 86 * (unsigned __int8)input_str[18]
+ 25 * (unsigned __int8)input_str[19]
+ 46 * (unsigned __int8)input_str[20];
cyphered[17] = 78 * (unsigned __int8)input_str[15]
+ 39 * (unsigned __int8)input_str[14]
+ 52 * (unsigned __int8)input_str[16]
+ 9 * (unsigned __int8)input_str[17]
+ 62 * (unsigned __int8)input_str[18]
+ 37 * (unsigned __int8)input_str[19]
+ 84 * (unsigned __int8)input_str[20];
cyphered[18] = 48 * (unsigned __int8)input_str[18]
+ 14 * (unsigned __int8)input_str[16]
+ 23 * (unsigned __int8)input_str[14]
+ 6 * (unsigned __int8)input_str[15]
+ 74 * (unsigned __int8)input_str[17]
+ 12 * (unsigned __int8)input_str[19]
+ 83 * (unsigned __int8)input_str[20];
cyphered[19] = 15 * (unsigned __int8)input_str[19]
+ 48 * (unsigned __int8)input_str[18]
+ 92 * (unsigned __int8)input_str[16]
+ 85 * (unsigned __int8)input_str[15]
+ 27 * (unsigned __int8)input_str[14]
+ 42 * (unsigned __int8)input_str[17]
+ 72 * (unsigned __int8)input_str[20];
cyphered[20] = 26 * (unsigned __int8)input_str[19]
+ 67 * (unsigned __int8)input_str[17]
+ 6 * (unsigned __int8)input_str[15]
+ 4 * (unsigned __int8)input_str[14]
+ 3 * (unsigned __int8)input_str[16]
+ 68 * (unsigned __int8)input_str[20];
cyphered[21] = 34 * (unsigned __int8)input_str[24]
+ 12 * (unsigned __int8)input_str[21]
+ 53 * (unsigned __int8)input_str[22]
+ 6 * (unsigned __int8)input_str[23]
+ 58 * (unsigned __int8)input_str[25]
+ 36 * (unsigned __int8)input_str[26]
+ (unsigned __int8)input_str[27];
cyphered[22] = 27 * (unsigned __int8)input_str[25]
+ 73 * (unsigned __int8)input_str[24]
+ 12 * (unsigned __int8)input_str[23]
+ 83 * (unsigned __int8)input_str[21]
+ 85 * (unsigned __int8)input_str[22]
+ 96 * (unsigned __int8)input_str[26]
+ 52 * (unsigned __int8)input_str[27];
cyphered[23] = 24 * (unsigned __int8)input_str[23]
+ 78 * (unsigned __int8)input_str[21]
+ 53 * (unsigned __int8)input_str[22]
+ 36 * (unsigned __int8)input_str[24]
+ 86 * (unsigned __int8)input_str[25]
+ 25 * (unsigned __int8)input_str[26]
+ 46 * (unsigned __int8)input_str[27];
cyphered[24] = 78 * (unsigned __int8)input_str[22]
+ 39 * (unsigned __int8)input_str[21]
+ 52 * (unsigned __int8)input_str[23]
+ 9 * (unsigned __int8)input_str[24]
+ 62 * (unsigned __int8)input_str[25]
+ 37 * (unsigned __int8)input_str[26]
+ 84 * (unsigned __int8)input_str[27];
cyphered[25] = 48 * (unsigned __int8)input_str[25]
+ 14 * (unsigned __int8)input_str[23]
+ 23 * (unsigned __int8)input_str[21]
+ 6 * (unsigned __int8)input_str[22]
+ 74 * (unsigned __int8)input_str[24]
+ 12 * (unsigned __int8)input_str[26]
+ 83 * (unsigned __int8)input_str[27];
cyphered[26] = 15 * (unsigned __int8)input_str[26]
+ 48 * (unsigned __int8)input_str[25]
+ 92 * (unsigned __int8)input_str[23]
+ 85 * (unsigned __int8)input_str[22]
+ 27 * (unsigned __int8)input_str[21]
+ 42 * (unsigned __int8)input_str[24]
+ 72 * (unsigned __int8)input_str[27];
cyphered[27] = 26 * (unsigned __int8)input_str[26]
+ 67 * (unsigned __int8)input_str[24]
+ 6 * (unsigned __int8)input_str[22]
+ 4 * (unsigned __int8)input_str[21]
+ 3 * (unsigned __int8)input_str[23]
+ 68 * (unsigned __int8)input_str[27];
cyphered[28] = 34 * (unsigned __int8)input_str[31]
+ 12 * (unsigned __int8)input_str[28]
+ 53 * (unsigned __int8)input_str[29]
+ 6 * (unsigned __int8)input_str[30]
+ 58 * (unsigned __int8)input_str[32]
+ 36 * (unsigned __int8)input_str[33]
+ (unsigned __int8)input_str[34];
cyphered[29] = 27 * (unsigned __int8)input_str[32]
+ 73 * (unsigned __int8)input_str[31]
+ 12 * (unsigned __int8)input_str[30]
+ 83 * (unsigned __int8)input_str[28]
+ 85 * (unsigned __int8)input_str[29]
+ 96 * (unsigned __int8)input_str[33]
+ 52 * (unsigned __int8)input_str[34];
cyphered[30] = 24 * (unsigned __int8)input_str[30]
+ 78 * (unsigned __int8)input_str[28]
+ 53 * (unsigned __int8)input_str[29]
+ 36 * (unsigned __int8)input_str[31]
+ 86 * (unsigned __int8)input_str[32]
+ 25 * (unsigned __int8)input_str[33]
+ 46 * (unsigned __int8)input_str[34];
cyphered[31] = 78 * (unsigned __int8)input_str[29]
+ 39 * (unsigned __int8)input_str[28]
+ 52 * (unsigned __int8)input_str[30]
+ 9 * (unsigned __int8)input_str[31]
+ 62 * (unsigned __int8)input_str[32]
+ 37 * (unsigned __int8)input_str[33]
+ 84 * (unsigned __int8)input_str[34];
cyphered[32] = 48 * (unsigned __int8)input_str[32]
+ 14 * (unsigned __int8)input_str[30]
+ 23 * (unsigned __int8)input_str[28]
+ 6 * (unsigned __int8)input_str[29]
+ 74 * (unsigned __int8)input_str[31]
+ 12 * (unsigned __int8)input_str[33]
+ 83 * (unsigned __int8)input_str[34];
cyphered[33] = 15 * (unsigned __int8)input_str[33]
+ 48 * (unsigned __int8)input_str[32]
+ 92 * (unsigned __int8)input_str[30]
+ 85 * (unsigned __int8)input_str[29]
+ 27 * (unsigned __int8)input_str[28]
+ 42 * (unsigned __int8)input_str[31]
+ 72 * (unsigned __int8)input_str[34];
cyphered[34] = 26 * (unsigned __int8)input_str[33]
+ 67 * (unsigned __int8)input_str[31]
+ 6 * (unsigned __int8)input_str[29]
+ 4 * (unsigned __int8)input_str[28]
+ 3 * (unsigned __int8)input_str[30]
+ 68 * (unsigned __int8)input_str[34];
cyphered[35] = 34 * (unsigned __int8)input_str[38]
+ 12 * (unsigned __int8)input_str[35]
+ 53 * (unsigned __int8)input_str[36]
+ 6 * (unsigned __int8)input_str[37]
+ 58 * (unsigned __int8)input_str[39]
+ 36 * (unsigned __int8)input_str[40]
+ (unsigned __int8)input_str[41];
cyphered[36] = 27 * (unsigned __int8)input_str[39]
+ 73 * (unsigned __int8)input_str[38]
+ 12 * (unsigned __int8)input_str[37]
+ 83 * (unsigned __int8)input_str[35]
+ 85 * (unsigned __int8)input_str[36]
+ 96 * (unsigned __int8)input_str[40]
+ 52 * (unsigned __int8)input_str[41];
cyphered[37] = 24 * (unsigned __int8)input_str[37]
+ 78 * (unsigned __int8)input_str[35]
+ 53 * (unsigned __int8)input_str[36]
+ 36 * (unsigned __int8)input_str[38]
+ 86 * (unsigned __int8)input_str[39]
+ 25 * (unsigned __int8)input_str[40]
+ 46 * (unsigned __int8)input_str[41];
cyphered[38] = 78 * (unsigned __int8)input_str[36]
+ 39 * (unsigned __int8)input_str[35]
+ 52 * (unsigned __int8)input_str[37]
+ 9 * (unsigned __int8)input_str[38]
+ 62 * (unsigned __int8)input_str[39]
+ 37 * (unsigned __int8)input_str[40]
+ 84 * (unsigned __int8)input_str[41];
cyphered[39] = 48 * (unsigned __int8)input_str[39]
+ 14 * (unsigned __int8)input_str[37]
+ 23 * (unsigned __int8)input_str[35]
+ 6 * (unsigned __int8)input_str[36]
+ 74 * (unsigned __int8)input_str[38]
+ 12 * (unsigned __int8)input_str[40]
+ 83 * (unsigned __int8)input_str[41];
cyphered[40] = 15 * (unsigned __int8)input_str[40]
+ 48 * (unsigned __int8)input_str[39]
+ 92 * (unsigned __int8)input_str[37]
+ 85 * (unsigned __int8)input_str[36]
+ 27 * (unsigned __int8)input_str[35]
+ 42 * (unsigned __int8)input_str[38]
+ 72 * (unsigned __int8)input_str[41];
cyphered[41] = 26 * (unsigned __int8)input_str[40]
+ 67 * (unsigned __int8)input_str[38]
+ 6 * (unsigned __int8)input_str[36]
+ 4 * (unsigned __int8)input_str[35]
+ 3 * (unsigned __int8)input_str[37]
+ 68 * (unsigned __int8)input_str[41];
for ( i = 0; i <= 41; ++i )
{
if ( cyphered[i] != Dst[i] )
{
printf("error");
exit(0);
}
}
printf("win");
return 0;
}
我们可以看出是7位一组进行加密，而且是使用了线性方程组的形式，解该线性方程组即可进行解密。
重复6次即可得到flag
102 108 97 103 123 55 101 49 55 49 100 52 51 45 54 51 98 57 45 52 101 49 56 45 57 57 48 101 45 54 101 49 52 99 50 97 102 101 54 52 56 125
flag{7e171d43-63b9-4e18-990e-6e14c2afe648}
我感觉应该有更快的方法。。比赛时几乎直接就秒了。。
要是有师傅有更优解可以给个提示。。感激不尽
来源：oschina
链接：https://my.oschina.net/u/4373790/blog/4526920