8.6. “QR9”: RUBIK’S CUBE INSPIRED AMATEUR CRYPTO-ALGORITHM
Prepare a pointer to the internal array again:
.text:005410A0 lea ebx, [esp+50h+internal_array_64]
.text:005410A4 mov edi, 7 ; EDI is loop 1 counter, initial state is 7
.text:005410A9
.text:005410A9 second_loop1_begin:
.text:005410A9 xor esi, esi ; ESI is loop 2 counter
.text:005410AB
.text:005410AB second_loop2_begin:
.text:005410AB mov al, [ebx+esi] ; value from internal array
.text:005410AE push eax
.text:005410AF push ebp ; arg_0
.text:005410B0 push edi ; loop 1 counter
.text:005410B1 push esi ; loop 2 counter
.text:005410B2 call set_bit
.text:005410B7 add esp, 10h
.text:005410BA inc esi ; increment loop 2 counter
.text:005410BB cmp esi, 8
.text:005410BE jl short second_loop2_begin
.text:005410C0 dec edi ; decrement loop 2 counter
.text:005410C1 add ebx, 8 ; increment pointer in internal array
.text:005410C4 cmp edi, 0FFFFFFFFh
.text:005410C7 jg short second_loop1_begin
.text:005410C9 pop edi
.text:005410CA pop esi
.text:005410CB pop ebp
.text:005410CC pop ebx
.text:005410CD add esp, 40h
.text:005410D0 retn
.text:005410D0 rotate1 endp
...thiscodeisplacingthecontentsoftheinternalarraytothecubeglobalarrayviatheset_bit()function,
butin a different order! Now the counter of the first loop is in the range of 7 to 0,decrementingat each
iteration!
The C code representation looks like:
void rotate1 (int v)
{
bool tmp[8][8]; // internal array
int i, j;
for (i=0; i<8; i++)
for (j=0; j<8; j++)
tmp[i][j]=get_bit (i, j, v);for (i=0; i<8; i++)
for (j=0; j<8; j++)
set_bit (j, 7-i, v, tmp[x][y]);
};
Not very understandable, but if we take a look atrotate2()function:
.text:005410E0 rotate2 proc near
.text:005410E0
.text:005410E0 internal_array_64 = byte ptr -40h
.text:005410E0 arg_0 = dword ptr 4
.text:005410E0
.text:005410E0 sub esp, 40h
.text:005410E3 push ebx
.text:005410E4 push ebp
.text:005410E5 mov ebp, [esp+48h+arg_0]
.text:005410E9 push esi
.text:005410EA push edi
.text:005410EB xor edi, edi ; loop 1 counter
.text:005410ED lea ebx, [esp+50h+internal_array_64]
.text:005410F1
.text:005410F1 loc_5410F1:
.text:005410F1 xor esi, esi ; loop 2 counter
.text:005410F3
.text:005410F3 loc_5410F3: