CrackMe CRK50CRK.ASM   by Independent (IND)

; How to use this crap: ; calculate the last two bytes for a given number of loops of his main loops ; calculate them as: 35d8h+132h+number_of_looops ; read it off with break points.. in softice or something ; a correct serial is: PJ/7 ; 25 loops is min. to make the last two bytes "typeable" but there is no values ; that first 25 loops.. 26 loops gives the PJ/7 serial .model small .stack 100h ; Plenty stack space .386 ; Who knows.. I might wanna use 386 code? .data sentence db 05,04 ; input from int21h/0ah db 0,0 ; Interate of these mother fuckers db 47,37h ; Bytes consistent with 26 loops : 35d8h+132h+26d db 0dh ; 0d terminated string - since read with int 21h/ah=0a count db 0 ; counter finish dw 0 ; place to store the current guess during iterations .code mov ax, @data ; Make DS&ES point to the DATA mov ds,ax mov es,ax xor dx,dx ; dx=0 next: lea bx, [sentence+2] ; let bx point to the bytes we're checking for a fit mov word ptr [bx],dx ; reset the bytes for next attempt inc word ptr [bx] ; next two bytes mov bx, word ptr [bx] ; fetch it push bx ; feed it to the call call flaffer ; try it! pop dx ; fetch attempt test ax,ax ; Did it work? jnz next ; no - try next mov ax,4c00h ; Breakpoint here - when it breaks DX=first two bytes int 21h flaffer: lea si,sentence mov cx,131h call again mov byte ptr [count],0 ret again: PUSH SI INC CX LODSW XCHG AX,BX LODSW ROL BX,CL XOR BX,AX XOR BX,CX MOV BP,[SI] LODSW MUL BX MOV [SI-04],AX POP SI inc byte ptr [count] cmp byte ptr [count],26h ; patch number of loops here je notagain ; OR AX,AX JNZ again ; ret notagain: ret end