# Protection of Digital Elevation Model--One Approach
## 2 Materials and Methods
### Applied Methodology  
The methodology applied in this research consists of nine steps: selection of security issues, analysis of security issues, attack impacts on security issues, assessment of consequences, assessment of the impact on DEM data changes, selection of security technology, creation of security model, model testing, and application and comparison of the model, Figure 2.  
Figure 1: Digital signing and digital signature verification procedure. Figure 2: Applied methodology for the creation of a model for non-repudiation and to protect DEM data. Selection of security questions. We selected security questions from a well-known model in the literature, the five pillars of the security model, which contains the following questions [43]:  
* Authenticity--the method of determining the identity of the user or entity. * Integrity--feature that the data has not been altered or destroyed in an unauthorized manner. * Confidentiality--the feature that the information is not available, nor is accessible to those who are not authorized to receive it. * Availability means that the data can be freely used when needed. * Non-repudiation--the impossibility of subsequently denying one's participation in all or only some parts of the completed transaction. Analysis of security issues. In this phase, we considered how to be sure that the DEM data is truly authentic--that it comes from a trusted source. We also looked at how to prevent someone else from presenting as an authentic source for DEM data. The integrity of DEM data is important because it assures us that the data has not been changed after creation, during storage, or transferred to another location. The implementation of the integrity mechanism does not prevent the data from being modified but enables the detection of the resulting data change. The issue of confidentiality is particularly important for security-sensitive systems that want DEM data to remain hidden from others. We consider the fulfillment of this question from point to point, that is, from the sender of DEM data to the recipient, and not only between their network devices. The goal is to make it impossible for an attacker to discover data during transmission from the sender to the recipient. The data is also protected at the storage location. We do not consider the availability of DEM data from the aspect of enabling uninterrupted access to the data, but whether the data is available for the interested party. Non-repudiation makes it impossible for the source to deny that the DEM data originated from him if the decisions made based on this data lead to damage. Likewise, the user cannot blame another source for the resulting damage. Therefore, the issue of non-repudiation should be carefully considered. Attack impacts on security issues. In this step, we looked at attacks that impact the above security issues. The most common authentication attacks are brute force, impersonate attacks and man-in-the-middle attacks. Data integrity attacks are hiding, replacing, modifying, and discarding attacks. Active attacks are traffic analysis, masking, and modification attacks. Attacks on confidentiality are man-in-the-middle, traffic analysis, and traffic monitoring attacks, whereas the most famous attacks on availability are denial of service (DoS) and distributed denial of service (DDoS) attacks. Assessment of consequences. In this step, we looked at the consequences of an attack on breaching security issues. The consequences of an authenticity violation lead the decisionmaker into the delusion that he received data from a reliable source, whereas an integrity violation leads to the use of wrong data. By violating trust, a competing party can gain insight into DEM data and, accordingly, gain dominance or other gains in the field. Failure to consider non-repudiation means that DEM data can be used, and the data source can deny that the data originated from it. Likewise, a user can use data from one source and blame another source for his failure because of using that data.