  The future communication will be characterized by ubiquitous connectivity and
security. These features will be essential requirements for the efficient
functioning of the futuristic applications. In this paper, in order to
highlight the impact of blockchain and 6G on the future communication systems,
we categorize these application requirements into two broad groups. In the
first category, called Requirement Group I \mbox{(RG-I)}, we include the
performance-related needs on data rates, latency, reliability and massive
connectivity, while in the second category, called Requirement Group II
\mbox{(RG-II)}, we include the security-related needs on data integrity,
non-repudiability, and auditability. With blockchain and 6G, the network
decentralization and resource sharing would minimize resource under-utilization
thereby facilitating RG-I targets. Furthermore, through appropriate selection
of blockchain type and consensus algorithms, RG-II needs of 6G applications can
also be readily addressed. Through this study, the combination of blockchain
and 6G emerges as an elegant solution for secure and ubiquitous future
communication.
