# Moving Towards Body-to-Body Sensor Networks for Ubiquitous Applications: A Survey
## 3 BBN Design Considerations
### Security Policies for BBN
First, the security mechanism for WBANs must be adjusted to the subsequent major security necessities which are divided into three classes (Figure 6):  
* Data storage: Confidentiality: while storing WBAN data, it should be encrypted and protected by access control lists. Integrity: WBAN data should be kept intact, unbroken while storage is performed. Dependability: WBAN data should be recovered after network incidents (link failure, deleted data, etc.). Privacy: unauthorized access to the stored WBAN data should be prohibited by the data storage policy. * Data access: Accountability: every malicious WBAN, that would access illegally to others' secured data, should be retrieved and held responsible of his actions. Revocability: malicious WBANs should be underprivileged at once. Non-repudiation: a source WBAN should not deny the generation of its own data. * Other security requirements: Authentication: any source WBAN should be authenticated by the destination, before sending the sensing data. Availability: the WBAN data should be available and accessible whenever it is needed. Then, specific mechanisms should be implemented to ensure a secure environment around the WBAN, which will detect, prevent and reinforce the WBAN against attacks. Existing security mechanisms for WBANs could be developed into seven aspects:  
1. Cryptography: cryptographic functions are used to ensure the safety and security of the information collected by sensor nodes (vital signs of a patient). Choosing the cryptographic system depends on the WBAN application and its energy consumption. 2. Key management: cryptographic keys are generated and shared to the WBANs to ensure secure communications. Three types of key management protocols can be found: the trusted server, considering a trusty base station to validate the key agreement, the key pre-distribution or the symmetric key cryptography, and finally, the public-key infrastructure. 3. Secure routing: the sensor node collects physiological information and sends this data to alternative devices. A number of routing protocols are proposed in the literature for sensor networks, but most of them suffer from security vulnerabilities that should be addressed to prevent inconsistency in the routed data. 4. Resilience to node capture: this is a major issue in WBANs, especially in real-time applications. For example, the public hospital environment could be targeted by malicious behaviors from the inside or the outside. To resolve this problem, one feasible solution is to use inviolable network hardware. 5. Trust management: corresponds to the partnership between two trustworthy WBANs that relay their respective data. 6. Secure localization: to facilitate mobility for patients, the authors specify in [78] localization procedures that operate over three steps: distance estimation, angle estimation and position computation. 7. Robustness to communication denial-of-services: the denial-of-service (DoS) attack can be implemented in the WBAN by broadcasting high-energy signals. Therefore, an energy-based security mechanism should be implemented to deal with this vulnerability. Finally, a number of industry and research projects have paid a special attention to the security issue in WBANs. In healthcare industry, the European MobiHealth project presented in [79] provides a detailed end-to-end ambulatory application using Bluetooth or ZigBee-based communication device, and is a single-hop network. The solution is deployed by UMTS and GPRS networks. The major issues are reliability and QoS guarantees. Figure 6: Major security requirements in BBNs. In the same context, CodeBlue project, introduced in [80], consists of the design of an ad hoc sensor wireless infrastructure to be deployed for emergency healthcare, in order to ensure efficient allocation of medical resources and seamless transfer of sensor data.