PPT-Cryptography Lecture 4 Arpita

Patra Quick Recall and Todays Roadmap gtgt CPA Security gt gt PRFbased construction gtgt Proof of Security gtgt Extension to CPAMULTsecurity gtgt Modes of Operations very efficient construction used in practice. However computational aspects of lattices were not investigated much until the early 1980s when they were successfully employed for breaking several proposed cryptosystems among many other applications It was not until the late 1990s that lattices w CS. . 111. Operating . Systems . Peter Reiher. . Outline. Basic concepts in computer security. Design principles for security. Important security tools for operating systems. Access control. Cryptography and operating systems. Josh Benaloh. Tolga Acar. Fall 2016. November 8, 2016. Practical Aspects of Modern Cryptography. 1. What is Money?. 106 billion people lived. 94% are dead. Most of the world’s wealth made after 1800. Week two!. The Game. 8 groups of 2. 5 rounds. Math 1. Modern history. Math 2. Computer Programming. Analyzing and comparing Cryptosystems. 10 questions per round. Each question is worth 1 point. Math Round 1. 1. Part I: Crypto. Chapter 2: Crypto Basics. MXDXBVTZWVMXNSPBQXLIMSCCSGXSCJXBOVQXCJZMOJZCVC. TVWJCZAAXZBCSSCJXBQCJZCOJZCNSPOXBXSBTVWJC. JZDXGXXMOZQMSCSCJXBOVQXCJZMOJZCNSPJZHGXXMOSPLH. JZDXZAAXZBXHCSCJXTCSGXSCJXBOVQX. Symmetric Encryption. Key exchange . Public-Key Cryptography. Key exchange. Certification . Why Cryptography. General Security Goal. - . Confidentiality . (. fortrolig. ). - . End-point Authentication . 1. Administrative Note. Professor Blocki is traveling and will be back on Wednesday. . E-mail: . jblocki@purdue.edu. . Thanks to Professor Spafford for covering the first lecture!. 2. https://www.cs.purdue.edu/homes/jblocki/courses/555_Spring17/index.html. Josh Benaloh. Tolga Acar. Fall 2016. October 25, 2016. 2. The wiretap channel. Key (K. 1. ). Key (K. 2. ). Eavesdropper. Plaintext. (P). Noisy insecure. channel. Encrypt. Decrypt. Alice. Bob. Plaintext. Cyclic group G of order q with generator g.  G.  . G = {g. 0. , g. 1. , …, g. q-1. }. For any h .  G, define . log. g. h .  {0, …, q-1} as. . log. g. h = x  . The . art and science of concealing the messages to introduce secrecy in . information security . is recognized as cryptography. .. The word ‘cryptography’ was coined by combining two Greek words, ‘Krypto’ . Crypto is amazing. Can do things that initially seem impossible. Crypto is important. It impacts each of us every day. Crypto is fun!. Deep theory. Attackers’ mindset. Necessary administrative stuff. . Patra. Quick Recall and Today’s Roadmap. >> Hash Function: Various Security Notions. >> . Markle-Damgaard. Domain . Extension. >> . Davis Meyer . Hash . function. >> Domain Extension for MAC using Hash function: Hash-and-Mac. . Patra. Quick Recall and Today’s Roadmap. >> Hash . Functions- stands in between public and private key world. >. > . Key Agreement. >> Assumptions in Finite Cyclic groups - DL, CDH, DDH. . Patra. Quick Recall and Today’s Roadmap. >> . CCA Security, more stronger than CPA security . >. > . Break of CBC Mode CPA secure scheme under CCA- Padding Oracle Attack. >> MAC.