Introduction to Cryptography: One-Time Pad and Public-Key Systems

This lecture provides an introduction to cryptography, focusing on the one-time pad, perfect secrecy, and public-key cryptography, particularly the Diffie-Hellman method. The instructor explains the fundamental purposes of cryptography, which are privacy and authenticity, emphasizing the importance of preventing sensitive information from falling into the wrong hands and ensuring that information is not falsified. The lecture covers the historical context of cryptography, including ancient systems like Caesar's cipher, and discusses modern cryptographic techniques. The one-time pad is presented as a method that achieves perfect secrecy, where the key is as long as the message and used only once. The instructor also addresses the vulnerabilities of various cryptographic systems and the significance of key management. The lecture concludes with a discussion on the implications of cryptography in the digital age, where sensitive information is frequently transmitted over public channels, necessitating robust security measures.