This lecture covers the fundamentals of public-key cryptography, including key exchange, forward secrecy, and signature schemes. It delves into topics such as Diffie-Hellman key exchange, RSA cryptography, and the quantum threat. The instructor also discusses real-world applications like the Signal messaging protocol, emphasizing confidentiality, authenticity, and deniability. The lecture concludes with a detailed explanation of signature schemes, including PKCS#1v1.5 encryption and signature verification. References to essential literature in the field are provided for further study.