The Internet of Things (IoT) has become pervasive in various domains and offers unprecedented convenience to society. The Narrowband Internet of Things (NB-IoT) technology is particularly well-suited for deployment in applications such as smart manufacturing, smart homes, and smart cities. However, NB-IoT requires low power consumption and network security, which pose significant challenges. While several cryptographic schemes have been proposed for NB-IoT, most of them are infeasible due to the high computing power required by the nodes. In this paper, we propose a secure obfuscation for encrypted identity-based signatures in NB-IoT. Our approach leverages the high computational power of the IoT gateway to generate an encrypted signature, while ensuring the node’s private key cannot be extracted. We prove that our scheme satisfies the virtual black box (VBB) properties and is secure against attacks by semi-honest gateways. Furthermore, we implement our scheme using the Java pairing-based cryptography library (JPBC) on a laptop and a server, and our experimental results demonstrate the practicality of our scheme in IoT applications.