Cryptography facilitates sharing of sensitive contents among the intended parties across any insecure network channels and prevents unintended recipients from knowing the secret information in the contents. Efforts are made to create tools for hiding information with modern cryptographic algorithms and security protocols. The technology is growing rapidly with public and private key cryptography for securing the sensitive information of organizations and performing online tasks with trusted parties. Many state-of-the-art cryptographic algorithms and protocols have been developed. For a promising researcher of this field, knowledge and understanding of the popular key algorithms and protocols is essential for developing a solid foundation for selecting a correct research direction. This chapter presents the key algorithms and protocols used in cryptography. The objective is to provide a technical description of key algorithms and protocols along with a basic understanding of the field.