Assembly Language for Beginners

(Jeff_L) #1

8.6. “QR9”: RUBIK’S CUBE INSPIRED AMATEUR CRYPTO-ALGORITHM


.text:005412F7 mov ecx, 10h
.text:005412FC mov esi, offset cube64
.text:00541301 add ebx, 40h
.text:00541304 cmp ebp, eax
.text:00541306 rep movsd
.text:00541308 jl short loc_5412D1
.text:0054130A mov edx, [esp+10h+Src]
.text:0054130E push edx ; Memory
.text:0054130F call _free
.text:00541314 add esp, 4
.text:00541317 pop edi
.text:00541318 pop esi
.text:00541319 pop ebp
.text:0054131A pop ebx
.text:0054131B retn
.text:0054131B decrypt endp
.text:0054131B
.text:0054131C align 10h
.text:00541320
.text:00541320 ; =============== S U B R O U T I N E =======================================
.text:00541320
.text:00541320
.text:00541320 ; int __cdecl crypt_file(int Str, char *Filename, int password)
.text:00541320 crypt_file proc near ; CODE XREF: _main+42
.text:00541320
.text:00541320 Str = dword ptr 4
.text:00541320 Filename = dword ptr 8
.text:00541320 password = dword ptr 0Ch
.text:00541320
.text:00541320 mov eax, [esp+Str]
.text:00541324 push ebp
.text:00541325 push offset Mode ; "rb"
.text:0054132A push eax ; Filename
.text:0054132B call _fopen ; open file
.text:00541330 mov ebp, eax
.text:00541332 add esp, 8
.text:00541335 test ebp, ebp
.text:00541337 jnz short loc_541348
.text:00541339 push offset Format ; "Cannot open input file!\n"
.text:0054133E call _printf
.text:00541343 add esp, 4
.text:00541346 pop ebp
.text:00541347 retn
.text:00541348
.text:00541348 loc_541348: ; CODE XREF: crypt_file+17
.text:00541348 push ebx
.text:00541349 push esi
.text:0054134A push edi
.text:0054134B push 2 ; Origin
.text:0054134D push 0 ; Offset
.text:0054134F push ebp ; File
.text:00541350 call _fseek
.text:00541355 push ebp ; File
.text:00541356 call _ftell ; get file size
.text:0054135B push 0 ; Origin
.text:0054135D push 0 ; Offset
.text:0054135F push ebp ; File
.text:00541360 mov [esp+2Ch+Str], eax
.text:00541364 call _fseek ; rewind to start
.text:00541369 mov esi, [esp+2Ch+Str]
.text:0054136D and esi, 0FFFFFFC0h ; reset all lowest 6 bits
.text:00541370 add esi, 40h ; align size to 64-byte border
.text:00541373 push esi ; Size
.text:00541374 call _malloc
.text:00541379 mov ecx, esi
.text:0054137B mov ebx, eax ; allocated buffer pointer -> to EBX
.text:0054137D mov edx, ecx
.text:0054137F xor eax, eax
.text:00541381 mov edi, ebx
.text:00541383 push ebp ; File

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