Wireless body area network (WBAN) is an emerging research field particularly in the area of remote health monitoring. For the simple reason that health data are private and sensitive information, securing access and data transmission within a WBAN becomes a critical need. Using certificates requires deploying Public Key Infrastructure (PKI) and Certification Authorities (CA) and their management~(control the generation, transmission and revocation) is a cumbersome task unlike identity-based cryptography concept. Considering the heterogeneity between participating tiers in the network, we propose in this paper a hybrid authentication and key agreement scheme where symmetric cryptography is used in sensor/actuator nodes while identity-based cryptography concept is used between smartphone (MN) and the storage site (SS). We present two protocols to authenticate and establish pairwise and group keys between all tiers and to provide a public and private keys for MNs.