1.47. Alice and Bob choose a key space K containing 256 keys. Eve builds a special- purpose computer that can check 10,000,000,000 keys per second. (a) How many days does it take Eve to check half of the keys in K? (b) Alice and Bob replace their key space with a larger set containing 2B different keys. How large should Alice and Bob choose B in order to force Eve's computer to spend 100 years checking half the keys? (Use the approximation that there are 365.25 days in a year.) For many years the United States government recommended a symmetric cipher called DES that used 56 bit keys. During the 1990s, people built special purpose computers demonstrating that 56 bits provided insufficient security. A new sym- metric cipher called AES, with 128 bit keys, was developed to replace DES. See Sect. 8.12 for further information about DES and AES.

1.47. Alice and Bob choose a key space K containing 256 keys. Eve builds a special- purpose computer that can check 10,000,000,000 keys per second. (a) How many days does it take Eve to check half of the keys in K? (b) Alice and Bob replace their key space with a larger set containing 2B different keys. How large should Alice and Bob choose B in order to force Eve's computer to spend 100 years checking half the keys? (Use the approximation that there are 365.25 days in a year.) For many years the United States government recommended a symmetric cipher called DES that used 56 bit keys. During the 1990s, people built special purpose computers demonstrating that 56 bits provided insufficient security. A new sym- metric cipher called AES, with 128 bit keys, was developed to replace DES. See Sect. 8.12 for further information about DES and AES.

College Algebra

7th Edition

ISBN:9781305115545

Author:James Stewart, Lothar Redlin, Saleem Watson

Publisher:James Stewart, Lothar Redlin, Saleem Watson

Chapter9: Counting And Probability

Section: Chapter Questions

Problem 3T: An Internet service provider requires its customers lo select a password consisting of four letter...

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