CHAPTER 79. “QR9”: RUBIK’S CUBE INSPIRED AMATEUR CRYPTO-ALGORITHM CHAPTER 79. “QR9”: RUBIK’S CUBE INSPIRED AMATEUR CRYPTO-ALGORITHM
.text:00541073 push ebx
.text:00541074 push ebp
.text:00541075 mov ebp, [esp+48h+arg_0]
.text:00541079 push esi
.text:0054107A push edi
.text:0054107B xor edi, edi ; EDI is loop1 counter
EBXis a pointer to the internal array:
.text:0054107D lea ebx, [esp+50h+internal_array_64]
.text:00541081
Here we have two nested loops:
.text:00541081 first_loop1_begin:
.text:00541081 xor esi, esi ; ESI is loop 2 counter
.text:00541083
.text:00541083 first_loop2_begin:
.text:00541083 push ebp ; arg_0
.text:00541084 push esi ; loop 1 counter
.text:00541085 push edi ; loop 2 counter
.text:00541086 call get_bit
.text:0054108B add esp, 0Ch
.text:0054108E mov [ebx+esi], al ; store to internal array
.text:00541091 inc esi ; increment loop 1 counter
.text:00541092 cmp esi, 8
.text:00541095 jl short first_loop2_begin
.text:00541097 inc edi ; increment loop 2 counter
; increment internal array pointer by 8 at each loop 1 iteration
.text:00541098 add ebx, 8
.text:0054109B cmp edi, 8
.text:0054109E jl short first_loop1_begin
...we see that both loops’ counters are in the range of 0..7. Also they are used as the first and second argument for the
get_bit()function. The third argument toget_bit()is the only argument ofrotate1(). The return value from
get_bit()is placed in the internal array.
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] ; EN(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