selfencrypt.asm

这是一个对自身代码进行实时加密的程序

; selfencrypt
; 04.07.2008

format PE GUI 4.0
entry start

;include "%include%/win32a.inc"
include "win32a.inc"
;
; This is the encryption macro.
; It is a simple XOR with 0xAA (10101010 in binary).
;
macro encrypt dstart,dsize {
    local ..char,..key,..shift
    repeat dsize
        load ..char from dstart+%-1
        ..char = ..char xor $AA
        store ..char at dstart+%-1
    end repeat
}

section ".code" code readable writeable executable
start:
        ;
        ; This will be the only non-encrypted part of the code.
        ; Here we will decrypt the code at run-time.
        ;
        mov     edx,real_start
        xor     eax,eax
        mov     ecx,code_size
@@:     xor     byte [edx],$AA
        inc     edx
        loop    @B

real_start:
        ;
        ; Everything from here on will be encrypted.
        ;
        stdcall [MessageBox],0,HelloWorld,HelloWorld,MB_ICONASTERISK

        stdcall [ExitProcess],0

        ;
        ; Encrypt everything from real_start to here.
        ;
        display "Encrypting code... "
        code_size = $ - real_start
        encrypt real_start,code_size
        display "done",13,10

section ".data" data readable writeable import
        library kernel32,"kernel32.dll",user32,"user32.dll"
        include "%include%/api/kernel32.inc"
        include "%include%/api/user32.inc"

        HelloWorld      db      "Hello World!",0