Security and Privacy in Body Sensor Networks - E-Healthcare Systems and Wireless Communications - page 111

Figure 5.Classification ECG features (Adapted from (Biel et al., 2001))

KEY AGREEMENT IN BSNS To communicate securely, the above mentioned

entities need to share a secret cryptographic key,
and thus need to participate in a key generation
and sharing protocol.
Key agreement between the BSN controller
and the base station and between the base station
and the backend server is easier to achieve than
that between the BSN sensor nodes. This is due
to the fact that the BSN controller, base station,
and backend server are relatively more capable
in terms of processing, memory, power, and com-
munication resources than individual body sensor
nodes. Thus these entities can execute a wide
variety of traditional security protocols based on
asymmetric-key cryptography such as the famous
Diffie-Hellman key agreement protocol (Diffie &
Hellman, 1976). Diffie-Hellman is a public-key
protocol that allows two communicating parities
A and B to share a secret key. The security of this
protocol is based on the difficulty of computing
discrete logarithms. Below we briefly describe
the operation of the Diffie-Hellman protocol. The
interested reader may refer to (Diffie, Hellman,
1976) for a detailed protocol description and
security analysis.
Initially the communicating entities A and
B share the knowledge of the following global
parameters: a large prime number p and an inte-
ger a that is a primitive root of p . To share a secret

Key agreement is the process that governs the gen-
eration and distribution of cryptographic keying
material in a secure communication network. It is
mainly required to support entity authentication
and data confidentiality and integrity protocols
in delivering their security services by supply-
ing these protocols with the necessary secret key
parameters. Key agreement is typically the most
complex phase in the design of any security pro-
tocol. The security of the data confidentiality and
integrity protocols mainly relies on the success
of the key management system in producing and
delivering secure cryptographic keys.
When considering the design of a security
protocol for a general BSN, we primarily focus
on securing the communication between the fol-
lowing entities in the network:

1. The communication between the BSN con-
troller and the wireless base station.
2. The communication between the wireless
base station and the enterprise backend
server in the healthcare unit.
3. The communication among the body sensor
nodes attached to or embedded in the human
body.