# Tokens Shuffling Approach for Privacy, Security, and Reliability in IoHT under a Pandemic
## 2 Related Work
Obfuscation approach [30]: it is used to protect privacy, especially for the user's location, as it replaces the user's actual site with a fake nearby location or hides it within a large area before sending the user's data to the service provider. It is also considered unsuitable for medical applications requiring accurate data, especially in pandemics, where the location is considered one of the most important data used to determine statistics and places of the epidemic or the spread of infection. Additionally, this approach is not concerned with the confidentiality or integrity of the data. Dummy approach [31]: it is used to preserve privacy by sending a lot of dummy data (false data) with the user queries and data. Thus, it is not suitable for medical applications, which need accurate data. Additionally, it does not have an interest in data confidentiality and integrity. In addition, it adversely affects performance. Anonymization using a pseudonym [32]: it is a simple approach to protecting privacy in which the user uses a pseudonym instead of his real name, but it is not effective if the user sends a lot of data or more than one query to the service provider. Additionally, this service does not care about the confidentiality and reliability of the data coming from unknown users. Therefore, it is not suitable for pandemics. This approach was developed with a different Mix-Zone approach where the pseudonym is changed periodically but is not considered a robust privacy protection approach and suffers from the same drawbacks as the traditional anonymization approach. Trusted Third-Party approach (TTP) [33]: it is a good approach used to ensure the privacy and security of data in addition to reliability, but if the third party is malicious, the same problem will be repeated for the malicious service provider, so it is not considered a sufficient solution or a guarantor alone, but it can be utilized and integrated with other methods, as we will see in the proposed approach. Cloak area approach [34]: it is used to protect the privacy of the user's site. It divides the area into cells such that, in each cell, there is a manager known as an anonymizer who hides the identity of all users in his area from the service provider and replaces their exact locations with his cell coordinates. Thus, this approach is not appropriate for health services in a pandemic for the same reasons that the obfuscation and dummy approaches are not appropriate. PIR approach [35]: it is used to protect the privacy and security of the data that reach the user from the service provider, not the opposite. Here, the user requests huge amounts of information from the service provider, and then the user works on it alone, which is therefore not suitable for the goals of health services during the pandemic. Cache approach [36]: it is a pro-privacy approach and is not considered sufficient when used independently. It is usually used to reduce the number of connections with the service provider and improve performance. Hybrid approach [37]: many methods can be combined to create a new approach with a higher level of privacy protection, but these approaches will not be valid in dealing with health services based on location. This is because they do not modify the mechanism of the main integrated methods, which are not suitable for health services, as we mentioned before. So, the hybrid approaches do not provide a solution for this research's main goal (preserving privacy under pandemic conditions without affecting the QoS). Thus, we note that there is a real need for a new approach capable of dealing with location-based services during pandemics, especially those related to the medical aspect, which is presented by this research. We used the TSA approach, which offers a new scenario that uses concepts used in the current approaches differently. TSA avoids the negatives that limit the effectiveness of previous methods during pandemics.