  The possibility of block chain innovation revolutionizing business operations
and interpersonal interactions in Industry 4.0 is becoming more widely
acknowledged. Industry 4.0 and the Industrial Internet of Things (IoT) are
among the new application fields. As a result, the purpose of this article is
to investigate the block chain applications that are already being used in IoT
and Industry 4.0. In particular, it looks at current research trends in various
IoT applications, addressing problems, concerns, and potential future uses of
integrating block chain technology. This article also includes a thorough
discussion of the key elements of block chain databases, including Merkle
trees, transaction management, sharding, long-term memory, and short-term
memory. In order to do this, more than 46 pertinent primary research that have
been published in reputable journals have been chosen for additional
examination. The workflow of a block chain network utilizing IoT is also
demonstrated, demonstrating how IoT devices communicate with one another and
how they contribute to the network's overall operation. The taxonomy diagram
below serves to illustrate the contribution.
