398
X. Liu et al.
However, the links are directed because they point from earlier transactions to
newer transactions, in a way called topological ordering. A DAG does not allow
loops. That means, a node is not allowed to traverse back to itself by following the
directed links. In this sense, a DAG is acyclic. Essentially, from the standing point of
computer science, a DAG is a graph with transactions being the nodes of the graph
and the edges which have directions.
Unlike blockchains, DAGs do not have blocks. There is no mining in DAGs.
Transactions provide validation for each other but a transaction cannot validate
itself. A new transaction is required to validate one or more previous transactions
when it joins the DAG. Every new transaction refers to its parent transactions, signs
their hashes, and includes the hashes in the new transaction.
8.1.5 Hybrid DLTs Based on Blockchains and DAGs
Blockchains and DAGs can be combined to create hybrid DLTs. An example of
hybrid DLTs is Bexam [8]. Bexam is a platform that leverages blockchain and DAG
technologies with greatly improved speed and scalability.
Bexam uses a flexible chain structure together with a node hierarchy so that it has
the security of a blockchain and the speed of a DAG with approximately 0.2 seconds
per block and about 40 million transactions per second. It is highly scalable because
it combines the concepts of DAG. Bexam uses a new consensus algorithm called
Proof-of-Rounds (PoR) and a KYC (Know Your Customer) verification process to
identify and prevent malicious actions. The electric power and computing resource
requirements of Bexam are also very low.
In addition, a token technology is used in Bexam for its transactions. It is
convenient to integrate Bexam into existing enterprise infrastructures.
8.1.6 Internet of Things (IoT)
Internet of Things is part of the Industry 4.0 revolution. IoT is a research and
industrial focus in recent years.
Essentially, IoT is all about having smart things which are equipped with sensors
and actuators collaborating over the Internet. IoT systems currently in use have a
centralized architecture where data is stored in the cloud. Cloud is a central place
with databases and services.
The IoT ecosystem is very complex. The complexity is due to the vast number
of devices connected, the types of wired and wireless communication networks
involved, and the varieties of software programs used. This complexity makes the
IoT ecosystem vulnerable and susceptible to attacks.
The current IoT ecosystem was developed largely based on available Internet
technologies in the past and did not have a systematically designed secure structure
X. Liu et al.
However, the links are directed because they point from earlier transactions to
newer transactions, in a way called topological ordering. A DAG does not allow
loops. That means, a node is not allowed to traverse back to itself by following the
directed links. In this sense, a DAG is acyclic. Essentially, from the standing point of
computer science, a DAG is a graph with transactions being the nodes of the graph
and the edges which have directions.
Unlike blockchains, DAGs do not have blocks. There is no mining in DAGs.
Transactions provide validation for each other but a transaction cannot validate
itself. A new transaction is required to validate one or more previous transactions
when it joins the DAG. Every new transaction refers to its parent transactions, signs
their hashes, and includes the hashes in the new transaction.
8.1.5 Hybrid DLTs Based on Blockchains and DAGs
Blockchains and DAGs can be combined to create hybrid DLTs. An example of
hybrid DLTs is Bexam [8]. Bexam is a platform that leverages blockchain and DAG
technologies with greatly improved speed and scalability.
Bexam uses a flexible chain structure together with a node hierarchy so that it has
the security of a blockchain and the speed of a DAG with approximately 0.2 seconds
per block and about 40 million transactions per second. It is highly scalable because
it combines the concepts of DAG. Bexam uses a new consensus algorithm called
Proof-of-Rounds (PoR) and a KYC (Know Your Customer) verification process to
identify and prevent malicious actions. The electric power and computing resource
requirements of Bexam are also very low.
In addition, a token technology is used in Bexam for its transactions. It is
convenient to integrate Bexam into existing enterprise infrastructures.
8.1.6 Internet of Things (IoT)
Internet of Things is part of the Industry 4.0 revolution. IoT is a research and
industrial focus in recent years.
Essentially, IoT is all about having smart things which are equipped with sensors
and actuators collaborating over the Internet. IoT systems currently in use have a
centralized architecture where data is stored in the cloud. Cloud is a central place
with databases and services.
The IoT ecosystem is very complex. The complexity is due to the vast number
of devices connected, the types of wired and wireless communication networks
involved, and the varieties of software programs used. This complexity makes the
IoT ecosystem vulnerable and susceptible to attacks.
The current IoT ecosystem was developed largely based on available Internet
technologies in the past and did not have a systematically designed secure structure