newbie question: any better way to write this code?

[neoedmund]

i want to let a byte array to be xor with some value.
but code show below i wrote seems not so .. good..., any better way to
write such function? thanks.
[code]
def xor(buf):
	bout=[]
	for i in range(len(buf)):
		x = ord(buf[i])
		x ^= 123
		bout.append(chr(x))
	return "".join(buf)
buf = "xxxxxxxx".encode("utf8")
buf = xor(buf)