With the rapid development of new internet technology and communication network, huge amounts of various digital data, for instance text message, image, audio signal and video with confidential information are exchanged via insecure network channels, which require a good cryptosystem that can resist any kind of attacks to ensure the information security. The cryptographic keys are crucial in cryptosystems. According to Kerckhoffs’ principle, the security of a cryptosystem should depend only on its key. Thus, they should have large key space and exhibit random properties to guarantee high security. Over the years, chaos-based Pseudo-Random Number Generators (PRNGs) have been verified to be efficient in producing pseudo-random numbers due to their excellent properties, such as, deterministic character, non-periodicity, high sensitivity to initial conditions and parameters, etc. Here, we propose to design and analyze a new robust Pseudo-Chaotic Number Generator (PCNG) based on discrete chaotic maps over finite field and a multiplexing mechanism.