A smart environment aims to enhance the quality of human life by improving simplicity and efficiency. IoT tools are general in nowadays computer networks. The IoT paradigm has recently evolved into a technology for creating smart environments. However, during this transmission, IoT devices are susceptible to cyber-attacks. Therefore, security as well as privacy is main concerns at real-world smart home environment applications. The major aim of manuscript is to propose Broken-Stick Regressive Lightweight Speck Ephemeral Cryptography-based Constrained Application Protocol (BRLSC-CoAP) for enhancing data security with minimal computational cost. First, the smart devices (i.e. IoT) deployed in homes to gather huge number of real-time information as well as broadcast it into authentic user. In order to improve data transmission with higher security, the proposed BRLSC-CoAP technique includes registration, encryption, authentication, and decryption. During the registration process, clients provide their information to server, and after that generates congruential ephemeral symmetric key. The encryption process employs the lightweight speck ephemeral cryptography algorithm to encrypt data with the help of a congruential ephemeral symmetric key. This algorithm is a lightweight symmetric key encryption designed to enhance the CoAP protocol in smart home applications. When the client accesses the data, authentication is performed before decryption. Forbes indexive Broken-stick regression is employed for user authentication. Normal clients access the data using the congruential ephemeral symmetric key, ensuring secure data communication with higher data confidentiality in the smart home. An experimental assessment of BRLSC-CoAP compared through conventional works and evaluated with respect to authentication accuracy, precision, confidentiality rate and computation cost. Also two comparison charts of lightweightness in terms of delay and overhead are measured to validate the entire process. The results indicate that the performance of BRLSC-CoAP increases 5% accuracy, 5% precision and higher 5% confidentiality rate with minimum 10% computation cost, 30% delay and 29% overhead than the conventional methods.