The ghost imaging (GI) approach is an intriguing and promising image acquisition technique that can transmit high-quality image information in a scattering environment. In this paper, we focus on two concerns recently emerged in the GI modality: one is the vulnerability to forgery attacks in GI-based optical encryption [Opt. Lett.45, 3917 (2020)OPLEDP0146-959210.1364/OL.392424], and the other is the potential threat of GI to personal privacy regarding non-invasive imaging [Opt. Express28, 17232 (2020)OPEXFF1094-408710.1364/OE.391788]. The core idea is to recommend introducing weighted multiplicative signals [Opt. Express27, 36505 (2019)OPEXFF1094-408710.1364/OE.27.036505] into the computational GI system, whether on the transmitting end or the receiving end. At the transmitting end, the random multiplicative signal can be used as an additional key that can reduce the possibility of forgery attacks, thereby increasing image transmission security. On the receiving end, the introduction of a random multiplicative signal to a spatial scattering medium makes it a "spatiotemporal" scattering medium, whose transmittance changes with time. Further, the spatiotemporal scattering medium can disable direct imaging and GI at the same time with low cost, thereby having great potential in privacy protection in daily lives.