**4. Blockchain limitations and future directions**

As a large number of scientific studies discussed in this chapter have shown, blockchain technology has become very popular in recent years, which may change the way people work and connect, and lay the basis for new requests using network devices. However, it has certain boundaries, such as:


Examples include low resource consumption, extensive interoperability, billions of nano-dealings, and data integrity because it is quicker, more energy and resource competent, and more resistant to quantization.

Tangle is an advanced transaction system and statistics argument layer intended to protect requests related to the Internet of Things. It is founded on a focused acyclic graph named Tangle, which is a typical information construction method. It aims to overcome approximately of the shortcomings of blockchain. In the tangled network, apiece transaction must be run PoW to confirm the previous two transactions. The basic theory is that the more transactions verified in parallel, the faster the network will expand. Tangle has the characteristics of scalability, resource optimization, data transmission safety, and quantum training. Tangle emerged as a third-generation crypto-currency, which does not require any additional costs to verify transactions, but is still safe. **Table 6** compares blockchain and entanglement.

Blockchain is less de-centralized than Tangle. Blockchain will likely link several IoT technologies to a single gateway, which will then take part in the blockchain network. This is known as a grouped or semi-decentralized method. It supports the idea that a small IoT device may participate directly in the tangle network.


#### **Table 6.**

*Blockchain and tangle comparison.*
