The blog post provides a guide on building a key exchange system using PubNub, which is part of a series on developing Babel, an open-source chat widget and API. Babel enables the exchange of 1024-bit RSA public keys and the transmission of self-destructing, encrypted messages in a chatroom. The tutorial outlines the initial steps, including signing up for a PubNub account, importing the PubNub JavaScript SDK, and initializing it with unique keys. It explains public key sharing through PubNub's Presence feature, allowing users to see who is online and exchange state information, facilitating encrypted messaging between users. The series aims to cover further topics like sending encrypted and self-destructing messages, and the post encourages readers to visit the newly launched Chat Resource Center for additional resources and tutorials on building and deploying mobile and web chat applications.