Douglas R. Stinson obtained his PhD in Combinatorics and Optimization from the University of Waterloo in 1981. He held academic positions at the University of Manitoba and the University of Nebraska-Lincoln before returning to Waterloo in 1998. In 2019, Dr. Stinson retired from the David R. Cheriton School of Computer Science at the University of Waterloo and he now holds the title Professor Emeritus. His research interests include cryptography and computer security, combinatorics and coding theory, and applications of discrete mathematics in computer science. He was elected as a Fellow of the Royal Society of Canada in 2011. He has published almost 400 papers and several books, including Cryptography: Theory and Practice, Fourth Edition, also published by CRC Press.