The document discusses the Advanced Encryption Standard (AES) which was selected by the U.S. government to encrypt sensitive data. It describes the requirements for AES, the evaluation criteria used in selecting it, and the five algorithm finalists. Rijndael, designed by Belgian cryptographers, was ultimately chosen as the AES cipher due to its security, performance, and simplicity. The summary provides an overview of the AES selection process and key aspects of the Rijndael cipher, including its round structure and efficient software implementations.