In cloud-assisted body area network (BAN), medical user (MU) is equipped with sensor nodes to measure different physiological health information (PHI). Whenever the PHI reading is found to be abnormal, BAN notifies this medical emergency event to cloud. Cloud broadcasts this medical emergency event to all medical service providers (MSPs) attached to cloud while preserving privacy of MU. There can be multiple MSPs competing for admitting the MU in need of medical treatment. For this, MSP uploads its infrastructural parameters to cloud. However, some MSPs can upload false data to cloud for attracting MU. This is
possible when malicious MSP is aware of some medical emergency event and ready to exploit the system to get more business. We classify this attack as Known Emergency Attack. This attack can severely deteriorate the appropriate MSP selection process during emergency. However, as per our knowledge, there is no prior work addressing this problem. We propose a
blockchain based framework, whcih can prevent an MSP from uploading false data and thereby protect from known emergency attack. In response to MU emergency, MSPs send its encrypted attributes to miners in the blockchain network. Miners compute encrypted difference between registered MSP attribute and currently received MSP attribute. If the difference is within a threshold, only then this MSP is considered as a candidate for MSP selection. Security and privacy of proposed framework is verified using Random Oracle Model and AVISPA tool. Computational requirement of proposed framework has also been evaluated.