Internet of Things (IoT) is now an integral part of our daily life. Smart devices are common in place which makes our life easy. It has revolutionized the way human interacts with devices. No doubt the IoT enabled devices have significantly changed our life. However there are various obstacles which need to be addressed to fully exploit the benefits of IoT devices and IoT enabled networks. IoT devices are generally not meant for complex processing and large storage capacity. It has limited power, processing and storage capacity. IoT devices are used in critical infrastructure and to communicate sensitive data. Security and privacy of IoT devices and data communication are important issues. But, because of the resource constraints existing security approaches are unsuitable for IoT devices. Recent development in blockchain technology offers promising solutions to overcome the IoT security and privacy challenges. However, integration of IoT with blockchain technology is not an easy task. Blockchain itself demands high storage and processing capacity. This paper presents blockchain based IoT framework balancing the resource constraints of IoT devices and resource demand of blockchain technology