PPT-Cryptography Lecture 17 Feistel

networks Feistel networks Build invertible permutation from noninvertible components One round Keyed round function f 01 n x 01 l 2 01 l 2 F k1 L0 R0 L1 R1. CS 465. Last Updated. : . Aug 25, 2015. Outline. Provide a brief historical background of cryptography. Introduce definitions and high-level description of four cryptographic primitives we will learn about this semester. The data encryption standard (DES). Online Cryptography Course Dan Boneh. Block ciphers: crypto work horse. E, D. CT Block. n. bits. PT Block. n. bits. Key. k Bits. 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. 1. Part I: Crypto. Chapter 2: Crypto Basics. MXDXBVTZWVMXNSPBQXLIMSCCSGXSCJXBOVQXCJZMOJZCVC. TVWJCZAAXZBCSSCJXBQCJZCOJZCNSPOXBXSBTVWJC. JZDXGXXMOZQMSCSCJXBOVQXCJZMOJZCNSPJZHGXXMOSPLH. JZDXZAAXZBXHCSCJXTCSGXSCJXBOVQX. 1. Part I: Crypto. Part 1 . . Cryptography . 2. Crypto. Cryptology . . The art and science of making and breaking “secret codes”. Symmetric Encryption. Key exchange . Public-Key Cryptography. Key exchange. Certification . Why Cryptography. General Security Goal. - . Confidentiality . (. fortrolig. ). - . End-point Authentication . Lect. . 6. : . Block . Ciphers. 2. Model of Symmetric Cryptosystem. E. D. Shared Secret Key. Shared Secret Key. Key. K. Secure Channel. Insecure Channel. Plaintext. M. Ciphertext . C. Plaintext. M. Richard J. Blech. Chief Executive Officer. Secure Channels, Inc.. Is there anyone here who cannot parse and explain this equation?. 2. If not, that’s ok.. 3. Why Pre-Computer Cryptography?. If you understand pre-computer crypto, you understand crypto!. 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. Steven M. Bellovin. https://www.cs.columbia.edu/~smb. What is Cryptography?. Literally: “hidden writing”. (Technical, the entire field is “cryptology”, but almost no one except the NSA and historians uses that word.). Consider first the case where there is no final key-mixing step. Possible to get the key immediately!. What about a full 1-round SPN? . Attack 1: for each possible . 1. st. -round. key, get corresponding 2. Feistel. networks. Feistel. networks. Build (invertible) permutation from . non-invertible. components. One round:. Keyed round function f: {0,1}. n. x {0,1}. l. /2. . {0,1}. l. /2. F. k1. (L0, R0) .