In this talk, I will be talking about cognitive radio networks (CRNs) and blockchain. Cognitive radio technology has been proposed and designed to meet the future wireless radio spectrum need of communications networks. With CRNs, the under-utilized wireless radio spectrum can be efficiently utilized using spectrum related functionalities. This dynamic spectrum management has been done traditionally using databases, however, with the blockchain technology, new opportunities can be realized in the management of this wireless radio spectrum. Blockchain can in fact help in achieving trust among different stake holders involved within the complete life cycle of dynamic spectrum management. Moreover, the trading of this wireless radio spectrum can be performed efficiently using blockchain. This short talk will cover all these aspects.