The Internet of Things (IoT) typically comprises sensors that have inadequate computational resources. On the contrary, blockchain technology is thought to be expensive in terms of resource consumption due to the consensus procedures involved. As a result, the application of blockchain to the IoT environment is a challenging task. The most appropriate solution lies in replacing the computationally heavy consensus algorithms with lightweight counterparts. Proof of authentication (PoAh) is the most suited replacement for such an environment. Several modifications have been proposed for PoAh during the last few years, and they are reviewed here.
In impoverished areas of some countries, it is common to see people begging or selling candies as their main income source. This is quite common on busy roads, and the transactions must be done quite quickly—usually limited to the period of a traffic light. The payments are made using coins. Beggars—or the self-employed, as seen from another angle—work hard, and there is no time to lose. Otherwise, money will not be earned.