# Hardware Countermeasures Benchmarking against Fault Attacks
## 5 Comparison between Different Protection Solutions
### Overall Comparison  
The trade-offs and relative comparison for each of the presented solutions are depicted in Figures 7 and 8. Figure 7 trade-off is considered between the degradation of the operating frequency versus the cost in terms of area. Figure 8 presents the trade-off between the F.C.C. and the Area-Delay-Product (ADP). The reference identified in both figures as [0] corresponds to the unprotected AES cipher and is used as a reference point. The green, yellow and red stripes in Figure 8 denote the ranges of highest to lowest level of protection, respectively, considering the fault coverage.  
In the analysis of frequency overhead vs. area cost (Figure 7) it is necessary to note that the solutions in Refs. [37; 46; 47; 48] by not presenting data on frequency degradation, they appear at the bottom. These data have been included in that figure because, although it is not possible to analyze them together with other solutions, it allows us to visualize the cost in area with respect to other countermeasures. For the analysis of fault coverage against the Area-Delay-Product (Figure 8) these solutions do not appear, since it is not possible to determine this factor.  
According to Figure 7 and focusing on the area consumption, it can be seen that the highest consumption countermeasures are those located above 30%, including hardware redundancy [35; 36], with [35] presenting the highest resource consumption. A second group of countermeasures between 10% and 30% is where most solutions are located. Finally, the solutions in [39; 41] that are below 10%. Regarding the operating frequency after adding the countermeasures, it can be seen that all are between 60% and 100%.  
Of these, the ones that offer the best performance, with 99.99% or 100% fault coverage, are [35; 38; 45; 49; 53]. Both [35; 45] offer the same operating frequency as the unprotected cipher, but with different implementation costs. In general, among all the countermeasures, the best trade-offs in terms of area and frequency are [38; 45].  
Figure 8: Fault Coverage vs. Area and Frequency overhead.  
Figure 7: Frequency degradation VS Area overhead of each countermeasure.  
Taking into account the values depicted in Figure 8, it can be seen that the countermeasures studied can be divided mainly into three groups. On the one hand, there are the countermeasures that offer a high level of security, between 90% and 100% fault coverage. Between 50% and 90% are the solutions that offer an intermediate level of security. Finally, there is the group of countermeasures with a low level of security, less than 50%. The countermeasures that are below 90%, medium and low level of protection, are due to the penalty that they suffer by not offering protection against all types of considered possible faults. For example, in the previous analysis it was possible to see how [39; 41] were the best proposals in term of costs, but in this analysis they fall significantly below 20% since they only consider one or two types of faults. Among the different proposals, in this case, it can be seen that the best options are [38; 45] because they offer 100% coverage and their ADP is less than 30%. By analysing [38; 45] in Figure 7, it can be seen that they present a very efficient trade-off, where the solution presented in [45] has an area cost bellow 20% and no frequency degradation. On the other hand, the [38] solutions present a small penalty in terms of frequency, but their area resources in the case of data item.2 in the table [38] is even lower than [45].