7. Implementation and evaluation
The system architecture illustrated in Fig. 1 is implemented for
experimental evaluation, with the main goal of secure and efficient
authentication and authorization as well as providing mobility
for the proposed end-to-end security scheme. To Implement
our proposed architecture, we setup a platform that consists
of medical sensors, UT-GATE smart e-health gateways, a remote
server, and end-users. UT-GATE is constructed from the combination
of a Pandaboard [40] and a Texas Instruments (TI) SmartRF06
board that is integrated with a CC2538 module [41]. The Pandaboard
is a low-power and low-cost single-board computer development
platform based on the TI OMAP4430 system-on-chip
(SoC) following the OMAP architecture and fabricated using 45 nm
technology. The OMAP4430 processor is composed of a Cortex-A9
microprocessor unit (MPU) subsystem including dual-core ARM
cores with symmetric multiprocessing at up to 1.2 GHz each. In
our configuration, UT-GATE uses 8 GB of external memory and is
powered by Ubuntu OS which allows to control devices and services
such as local storage and notification. To investigate the feasibility
of our proposed architecture, the Wismote [42] platform,
which is a common resource-limited sensor, is utilized in Contiki’s
network simulation tool Cooja [14]. Wismote is equipped
with a 16 MHz MSP430 micro-controller, an IEEE 802.15.4 radio
transceiver, 128 kB of ROM, 16 kB of RAM, and supports
20-bit addressing. For the evaluation, we use the open source
tool OpenSSL version 1.0.1.j to create elliptic curve public and
private keys from the NIST P-256 (prime256v1) and X.509 certificates.
X.509 certificates are the prevailing form of certificates
and are employed in the certificate-based mode of DTLS [43]. The
server association to the end-user is created using OpenSSL API