#17 Building Cryptography | Part 1 | Quantum Algorithms & Cryptography

Welcome to 'Quantum Algorithms & Cryptography' course ! This lecture delves into the principles of cryptographic design, examining how to build secure cryptographic systems and what guarantees they can provide. The lecture starts by posing questions about the construction, guarantees, intuitive ideas, mathematical definitions, and real-world applicability of cryptographic systems. The lecture emphasizes the importance of mathematically rigorous security analysis in cryptography, arguing that while practical considerations are important, mathematical proofs provide stronger and more reliable security guarantees. The lecture outlines the three core principles of cryptographic design: formulating a rigorous security model, establishing precise mathematical assumptions, and constructing the cryptosystem with a proof of security based on the assumptions. The lecture acknowledges the existence of side-channel attacks that exploit implementation details but focuses primarily on the mathematical security model. The lecture then takes symmetric-key encryption as a case study. The lecture systematically analyzes different intuitive notions of security for symmetric-key encryption, pointing out their flaws and leading to the definition of indistinguishability under chosen-plaintext attack (IND-CPA). The lecture briefly discusses the concept of security parameters, emphasizing the need for them to be large enough to provide practical security guarantees. Finally, the lecture revisits the three principles of cryptographic design in the context of symmetric-key encryption, highlighting the choice of hard problems, security models, and the role of reductions in proving security. NPTEL Courses permit certifications that can be used for Course Credits in Indian Universities as per the UGC and AICTE notifications. To understand various certification options for this course, please visit https://nptel.ac.in/courses/106106241 #Cryptography #CryptographicDesign #SecurityModel #MathematicalAssumption #Reduction #SymmetricKeyEncryption