[Jochen]

Here's an example on how you can move bytes to memory instead of using the normal WinAPI.

Code:

include 'win32ax.inc'

buf db  0x3A, 0x9C, 0x00, 0xE6, 0xB5, 0xE6, 0xE1, 0xE7, 0xFC, 0xFB, 0xF2, 0xB5,\
        0xE2, 0xF4, 0xE6, 0xB5, 0xF0, 0xFB, 0xF6, 0xE7, 0xEC, 0xE5, 0xE1, 0xF0,\
        0xF1, 0xB5, 0xF7, 0xF0, 0xF3, 0xFA, 0xE7, 0xF0, 0x95
buflen = $ - buf

Dst rb buflen; Give Dst the space it needs

main:
     stdcall XorStr, buf, buflen, 0xfc9d9a6e
     stdcall CopyMem,Dst,buf,buflen
     invoke MessageBox,0,Dst,'CopyMem',MB_OK
     invoke ExitProcess,0
.end main


proc CopyMem lpDest:DWORD, lpSrc:DWORD, lpLen:DWORD
mov esi, [lpSrc]
mov edi, [lpDest]
mov ecx, [lpLen]
rep movsb
ret
endp

proc XorStr Start, Size, Key
pushad
mov  esi,[Start]
mov  eax,[Key]
mov  ecx,[Size]
@@: xor  dword [esi],eax
inc  esi
loop @B
popad
leave
retn
endp