Cracking 2/Cracking II..iso/Texty/crackme/CRC.ASM

Assembly Source File | 1999-01-28 | 3.8 KB | 271 lines

;
;    This programm is extremelly slow. Don't run it.
;    It is only for example for step 2.
;
    .model tiny
    .486
    .code
    .startup
    org 100h

    jmp @0

        include msg.inc
        include debug.inc

UpdateBytes    macro
    mov edx,newcrc
    movzx ebx,byte ptr [Key0]
    xor   bl,dl
    shr edx,8
    xor edx,Magic32[ebx*4]

    movzx ebx,byte ptr [Key1]
    xor   bl,dl
    shr edx,8
    xor edx,Magic32[ebx*4]

    mov bl,byte ptr [Key2]
    xor   bl,dl
    shr edx,8
    xor edx,Magic32[ebx*4]

    mov bl,byte ptr [Key3]
    xor   bl,dl
    shr edx,8
    xor edx,Magic32[ebx*4]

    mov bl,byte ptr [Key4]
    xor   bl,dl
    shr edx,8
    xor edx,Magic32[ebx*4]

    mov al,dl
    xor al,crc4i
    mov _b1,al
    shr edx,8
    xor edx,dword ptr crc4

    mov al,dl
    xor al,crc3i
    mov _b2,al
    shr edx,8
    xor edx,dword ptr crc3

    mov al,dl
    xor al,crc2i
    mov _b3,al
    shr edx,8
    xor edx,dword ptr crc2

    mov al,dl
    xor al,crc1i
    mov _b4,al
endm

_real32    dword 0

NewCrc    dword 0
crc16    word 0

FullCrc:
    _d    byte 0
    _c    byte 0
    _b    byte 0
    _a    byte 0
Crc1:
    _4    byte 0
    _3    byte 0
    _2    byte 0
    _1    byte 0
Crc2:
        byte 0
    _7    byte 0
    _6    byte 0
    _5    byte 0
Crc3:
        byte 0
        byte 0
    _9    byte 0
    _8    byte 0
Crc4:
        byte 0
        byte 0
        byte 0
    _10    byte 0

Crc1i        byte 0
Crc2i        byte 0
Crc3i        byte 0
Crc4i        byte 0

Key        byte 256-8-1 dup(0)

Key0        byte 1
Key1        byte 0
Key2        byte 0
Key3        byte 0
Key4        byte 0

_b1        byte 0
_b2        byte 0
_b3        byte 0
_b4        byte 0

;_ebx        dword 0
;_h        word 0
;log        byte 'crclog',0

Magicon        equ 0edb88320h

Magic32        dword 256 dup(1)
Cache32        byte 256 dup(2,2,2,2,2)

@0:

    call InitMagic32

    mov eax,_real32
    mov dword ptr FullCrc,eax

    mov edx,0
    lea si,Key
    mov cx,256-8-1
    cld
    xor ebx,ebx
@10:    mov bl,byte ptr [si]
    inc si
    xor bl,dl
    shr edx,8
    xor edx,Magic32[ebx*4]
    loop @10
    mov dword ptr newcrc,edx
    call CalcBytes

    mov eax,12340000h
    push 0B800h
    pop gs

@e2:

    push eax
    mov dword ptr Key1,eax

    UpdateBytes

    xor eax,eax
    xor ebx,ebx
    mov    si, offset Key0-3

    REPT 9
        local @@1
        movsx   cx,byte ptr [si]
        mov     ax,[si+1]

        inc    si
        mul    cx

        mov    cl, [si+2]
    @@1:    rol    eax, cl
        xor    ebx, eax
        push    cx
        movsx    cx, al
        rol    ebx, cl
        pop    cx
        not    eax
        loop    @@1
    ENDM

    cmp    ebx, 0A69EC24Eh
    jz    @ok

    pop eax
    inc al
    jnz @e2
    mov byte ptr gs:[0],ah
    inc ah
    jnz @e2

    @Message 'fuck! ',0
    retn


@ok:    pop eax
    lea si,Key1
    mov cx,8
@ok2:    lodsb
    call $ShowAL
    $ShowSymb ' '
    loop @ok2
    call $Next_Line
    lea dx,fname
    mov ax,3C00h
    xor cx,cx
    int 21h
    xchg ax,bx
    lea dx,Key
    mov cx,256
    mov ah,40h
    int 21h
    mov ah,3Eh
    int 21h
    retn
fname    db '!ok!',0

InitMagic32:
                std
                mov     di,OFFSET Magic32+0400h-4    ; Last WORD of the array
                mov     dx,0FFh
im0:            mov     cx,8
                movzx    eax,dx
im1:            shr     eax,1
                jnc     im2
                xor     eax,Magicon
im2:            loop    im1
                stosd
                push eax
                shr eax,24
                lea si,Cache32[eax+eax*4]
                pop dword ptr [si]
                mov [si+4],dl
                dec     dx
                jns     im0
                cld
                ret
CalcBytes:
    movzx eax,_a
    mov cl,Cache32[eax*4+eax+4]
    mov eax,dword ptr Cache32[eax*4+eax]

    mov dword ptr crc1,eax
    mov crc1i,cl

    movzx eax,_b
    xor al,_2
    mov cl,Cache32[eax*4+eax+4]
    mov eax,dword ptr Cache32[eax*4+eax]
    mov dword ptr crc2,eax
    mov crc2i,cl

    movzx eax,_c
    xor al,_3
    xor al,_6
    mov cl,Cache32[eax*4+eax+4]
    mov eax,dword ptr Cache32[eax*4+eax]
    mov dword ptr crc3,eax
    mov crc3i,cl

    movzx eax,_d
    xor al,_4
    xor al,_7
    xor al,_9
    mov cl,Cache32[eax*4+eax+4]
    mov eax,dword ptr Cache32[eax*4+eax]
    mov dword ptr crc4,eax
    mov crc4i,cl
    retn


end