6 One-Time Pads nonrepeating series of numbers Exclusive Exclusive oR or other Plaintext bining Ciphertext oR or other O riginal g combining Plaintext function function From Security in Computing, Fifth Edition, by Charles P Pfleeger, et al. (ISBN: 9780134085043) Copyright 2015 by Pearson Education, Inc. All rights reserved
One-Time Pads 6 From Security in Computing, Fifth Edition, by Charles P. Pfleeger, et al. (ISBN: 9780134085043). Copyright 2015 by Pearson Education, Inc. All rights reserved
7 Shannon's Characteristics of good Ciphers The amount of secrecy needed should determine the amount of labor appropriate for the encryption and decryption 2. The set of keys and the enciphering algorithm should be free from complexity 3. The implementation of the process should be as simple as possible 4. Errors in ciphering should not propagate and cause corruption of further information in the message 5. The size of the enciphered text should be no larger than the text of the original message From Security in Computing, Fifth Edition, by Charles P Pfleeger, et al. (ISBN: 9780134085043) Copyright 2015 by Pearson Education, Inc. All rights reserved
Shannon’s Characteristics of Good Ciphers 1. The amount of secrecy needed should determine the amount of labor appropriate for the encryption and decryption 2. The set of keys and the enciphering algorithm should be free from complexity 3. The implementation of the process should be as simple as possible 4. Errors in ciphering should not propagate and cause corruption of further information in the message 5. The size of the enciphered text should be no larger than the text of the original message 7 From Security in Computing, Fifth Edition, by Charles P. Pfleeger, et al. (ISBN: 9780134085043). Copyright 2015 by Pearson Education, Inc. All rights reserved
8 Properties of a Trustworthy Cryptosystem It is based on sound mathematics It has been analyzed by competent experts and found to be sound It has stood the test of time From Security in Computing, Fifth Edition, by Charles P Pfleeger, et al. (ISBN: 9780134085043) Copyright 2015 by Pearson Education, Inc. All rights reserved
Properties of a Trustworthy Cryptosystem • It is based on sound mathematics • It has been analyzed by competent experts and found to be sound • It has stood the test of time 8 From Security in Computing, Fifth Edition, by Charles P. Pfleeger, et al. (ISBN: 9780134085043). Copyright 2015 by Pearson Education, Inc. All rights reserved
9 DES Algorithm Left Data [ lalf Right Data Half 56 bits Expansion Substitution Permutation New Left Data Ilalf New Right Data Halr From Security in Computing, Fifth Edition, by Charles P Pfleeger, et al. (ISBN: 9780134085043) Copyright 2015 by Pearson Education, Inc. All rights reserved
DES Algorithm 9 From Security in Computing, Fifth Edition, by Charles P. Pfleeger, et al. (ISBN: 9780134085043). Copyright 2015 by Pearson Education, Inc. All rights reserved
DES Algorithm(cont) Cyl: 2 inha Prrmdhn From Security in Computing, Fifth Edition, by Charles P Pfleeger, et al. (ISBN: 9780134085043) Copyright 2015 by Pearson Education, Inc. All rights reserved
DES Algorithm (cont.) 10 From Security in Computing, Fifth Edition, by Charles P. Pfleeger, et al. (ISBN: 9780134085043). Copyright 2015 by Pearson Education, Inc. All rights reserved