Multiprocessor System-on-Chip (MPSoC) design is based on the integration of several third-party Intellectual Property (IP) cores. Some of those IPs may include Trojans, extra hardware that can be triggered during operation time in order to perform an attack. Network-on-Chip (NoC), the communication IP of MPSoCs, can include Trojans that spy, modify and constrain the sensitive communication inside the chip. Although previous works address the malicious NoC threat, finding secure and efficient solutions is still a challenge. In this work, we propose a novel and secure network interface which implements a tunnel-based protocol that enables the secure exchange of sensitive data even in the presence of a malicious NoC. We test our technique with synthetic traffic as well as in several real application scenarios, and show that it is a secure and efficient solution.