function rc4_init(key, key_size)
    local trans = {}
    local i, j
    
    for i = 0, 255 do
	trans[i] = i
    end
    
    j = 0
    
    for i = 0, 255 do
	j = bin.imod((j + trans[i] + key[bin.imod(i, key_size) + 1]), 256)
	trans[i], trans[j] = trans[j], trans[i]
    end
    
    trans.i = 0
    trans.j = 0
    
    function trans:GenOut()
	self.i = bin.imod(self.i + 1, 256)
	self.j = bin.imod(self.j + self[self.i], 256)
	self[self.i], self[self.j] = self[self.j], self[self.i]
	
	return self[bin.imod(self[self.i] + self[self.j], 256)]
    end
    
    function trans:scramble(stream, stream_size)
	for i = 1, stream_size do
	    stream[i] = bin.bxor(stream[i], self:GenOut())
	end
	
	return stream
    end
    
    return trans
end

--[[

rc4_test_key = {
    25,
    68,
    153,
    64,
    32,
    129,
    39,
    202,
}

rc4_test_message = {
    1,
    2,
    3,
    4,
    5,
    6,
    7,
    8,
    1,
    2,
    3,
    4,
    5,
    6,
    7,
    8,
}

rc4_test_message_enc = {
    97,
    229,
    213,
    202,
    178,
    220,
    16,
    247,
    75,
    226,
    135,
    179,
    111,
    12,
    30,
    123,
}
    
function rc4_test()
    local trans, enc, dec, i
    
    trans = rc4_init(rc4_test_key, 8)
    
    enc = trans:scramble(rc4_test_message, 16)
    
    for i = 1, 16 do
	assert(enc[i] == rc4_test_message_enc[i])
    end
    
    trans = rc4_init(rc4_test_key, 8)
    
    dec = trans:scramble(enc, 16)
    
    for i = 1, 16 do
	assert(dec[i] == rc4_test_message[i])
    end
end

]]