# Internet of Things and Blockchain Integration: Security, Privacy, Technical, and Design Challenges
## 3 RQ 1 and RQ 2--Current Challenges and Recommendations to Enhance BIoT Integration
### BC-Based Security Issues
#### 3.1.6 Trust Management  
While actual collaboration is required to complete specific services and operations, establishing trustworthy cooperation and confidence in an IoT system is difficult as each node can join and exit the system at any moment, and nodes' identities can be anonymous [66; 126]. Accordingly, trust management is among the key challenges when adopting BioT as IoT needs to connect hundreds of devices to form P2P data delivering and sharing [12; 85]. The following are some of the trust difficulties that have been found in the literature:  
1. Trusting the software updates for fog node devices and trusting the owners of those devices are among the most common challenges for IoT device permissions and communications when using BC [68; 82].
2. Another challenge related to trust is granularity (i.e., resolution of the measured and recorded physical quantity), which is the amount of confidence that should be placed in the party providing the service and the extent to which the service receiver to pay for is trusted. For example, if an electric grid service provider wishes to be paid for every watt of electricity provided as it is provided, this may place undue stress on the system [107].
3. Another related problem is that it is difficult to implement real transaction validation. For example, a service provider could send out 10 W of electricity, but the receiver might only report 9 W. What is the best way to deal with this collision? The meters must be calibrated. Then, an independent method of determining the quantity of power sent and received is required [69].
4. Lastly, because of the trust difficulties, rating agencies may be able to give information on trust. This is similar to how online marketplaces like eBay employ ratings for sellers and customers. The resolution of trust takes place outside of the BC environment. As a result, while sending and receiving a specific quantity of Bitcoin is guaranteed, the service it may represent is not [69].  
To mitigate the challenge of trust, a global reputation assessment model based on BC technology to improve the efficacy of the above trust models can be used [66]. Establishing a node assessment mechanism grounded on irreversible block data is one such option. First, with BC technology, any node in the block can obtain the behavior data of other nodes. The reputation of the nodes would be computed automatically after inserting their activity data into the reputation evaluation algorithm. When calculating reputation, the kind of behavior and timeliness should be taken into account, since these two factors represent the node's performance over time and impact the ultimate reputation distribution [66]. As a result, while choosing the appropriate sort of behavior and timescale, it is critical to consider the nodes' motivations and preferences to effectively govern node behavior and develop trust [66; 67]. Moreover, since the BC is unable to validate external data, it must be digitized to achieve its full worth. There are two types of solutions that might be considered. One is the addition of a third party who can vouch for the accuracy of the input data. However,part of the decentralization feature may be sacrificed as a result. Another option is to use innovative approaches to tackle asset digitization challenges. This may need the creation of IoT devices capable of enabling exclusive identification [27].