The underlying vision of the internet of things (IoT) is to create a world where the real and the virtual realms are converging to create smart environments that makes energy, transport, cities, and many other areas more intelligent. With the IoT, the physical world is being interfaced through the things to the virtual world in heterogeneous environment. In heterogeneous environment, privacy and security are the major challenges. The secure information exchange is most critical pitfall to ensure the system security. This chapter gives a detailed analysis of cryptographic algorithms in IoT. A comparison of lightweight cryptography algorithms on basis of block size, key size, gate equivalents, and throughput is given. Moreover, the various security issues in IoT are discussed along with possible solution.