Crackme's are Lame   by Independent (IND)

; Crackme's are Lame ; So why did I write on? Because I'm a lamer! ; POINT IS: it's easy to make good protection even with small means. ; BTW: the possibility for possible complexity expands geometrically with ; the number of chars you use... Write an algorithm in the spirit of this one ; with 10 chars and you might aswell forget about finding a key ; (BTW the rules is: No patching.. only Keys!) ; While this algorithm because of only one letter used is fully reversible ; algorithms of this type with multiple letters are not! ; Btw.. it takes some 120 binary calculations to reverse engeneer this :) model tiny .Code ; Code starts Org 100h ; COM! Start: .386 mov dx, offset intro call write mov dx, offset input mov ax,0a00h int 21h mov dx, offset string1 mov eax, 'STEN' ; Keycheck movzx ecx, byte ptr [char] loopme: rol eax,6 xor ah,al add al, cl loop loopme cmp eax, 0d62722e8h jz done mov dx, offset string2 done: call write ret ; Terminate write PROC mov ah,9h int 21h ret write ENDP intro db 'Type yer attempt: $' string1 db 10,13,'Right!$' string2 db 10,13,'Wrong!$' input db 2,0 char db 0,0 End Start