# Feasibility Assessment of a Fine-Grained Access Control Model on Resource Constrained Sensors
## 5 Performance Evaluation
### Performance Analysis
#### 5.2.2 Energy Consumption  
Considering the impact of the Hidra protocol on the energy consumption in the CDS, Table 11 shows the measured values of the power consumption related to seven series of 80 security association establishments. Such mean energy consumptions grow slightly with the length of the policy instances, as expected, ranging from 0.367 uAh (\(IS_{1}\) and APBR) to 0.520 uAh (\(IS_{3}\) and CBOR), which are very low values.  
Figure 9 shows that the measured average values of the power consumption remain below a very low maximum and are proportional to the length of the enforced policy instances. The proportionality is better appreciated in Figure 10, where a rising trend is depicted. These very good results mean  
\begin{table}
\begin{tabular}{l l c c c c c} \hline \hline \multirow{2}{*}{**IS**} & \multirow{2}{*}{**Format**} & **Length** & **Average** & **Median** & **Standard** & **95\% Configuration** \\  & & **(Byte)** & **(uAh)** & **(uAh)** & **Deviation (uAh)** & **Int. (uAh)** \\ \hline \(IS_{1}\) & APBR & 2 & 0.3671 & 0.3510 & 0.0491 & (0.3563,0.3779) \\ \(IS_{2}\) & APBR & 7 & 0.3720 & 0.3709 & 0.0246 & (0.3666,0.3774) \\ \(IS_{3}\) & APBR & 9 & 0.3722 & 0.3719 & 0.0123 & (0.3694,0.3748) \\ \(IS_{4}\) & APBR & 32 & 0.4567 & 0.4491 & 0.0122 & (0.4541,0.4594) \\ \hline \(IS_{1}\) & CBOR & 14 & 0.4316 & 0.4204 & 0.0368 & (0.4236,0.4397) \\ \(IS_{2}\) & CBOR & 81 & 0.4898 & 0.4803 & 0.0122 & (0.4871,0.4925) \\ \(IS_{3}\) & CBOR & 123 & 0.5204 & 0.5069 & 0.0122 & (0.5179,0.5233) \\ \hline \hline \end{tabular}
\end{table}
Table 11: Energy consumption measures.  
Figure 8: Response time of security association establishment considering two series of 80 requests with \(IS_{1}\) in two network configurations: one and two hops.  
that the impact of Hidra in terms of energy consumption is very low and that the high compression factor of the proposed policy codification is a critical success factor. Concretely, in the case of two AAA batteries with a capacity of 900 mAh, totaling 1800 mAh, considering a 95% battery performance, representing a real capacity of 1710 mAh, more than 4 million (4,291,006) requests could be handled during the battery lifetime.  
In the envisioned scenario, the CDS is accessed by the subject to perform tasks such as personalization, parametrization, updating, upgrading, and maintenance. These types of interactions do not occur often. As the most exigent scenario, we can consider the case of different subjects requesting access every hour to tune the user experience in an application whereby the users change hourly.  
Figure 10: Energy consumption in security association establishment considering 80 requests in a one-hop network configuration.  
Figure 9: Energy consumption in security association establishment considering 80 requests in a one-hop network configuration.  
In this most exigent scenario, a subject making one request per hour, totaling 24 requests per day, 8760 requests per year, could obtain a response for approximately 490 years (489.840) with the given battery life. Therefore, the energy consumption of Hidra could be ignored, and the battery life would depend basically on the main application purpose of the CDS.