The topic discussed in this chapter are: We will explore the need, features and characteristics of public key cryptography; the working/function of a public key cryptography scheme will be discussed in detail; RSA, as an example, will be explained. | Network Security Lecture 17 Presented by: Dr. Munam Ali Shah Summary of the Previous Lecture We discussed stream ciphers and its working We explored how stream ciphers are efficient when compared to block ciphers in terms of performance Some examples of stream ciphers such as RC4, RC5 and blowfish etc. were explored Summary of the previous Lecture Stream Cipher Properties some design considerations are: long period with no repetitions statistically random depends on large enough key large linear complexity use of highly non-linear boolean functions Ci = Mi XOR StreamKeyi 3 Criteria from Rueppel Stream Cipher Illustration Summary of the Previous Lecture (RC4) a proprietary cipher owned by RSA another Ron Rivest design, simple but effective variable key size (1-256 bytes) byte-oriented stream cipher widely used (web SSL/TLS, wireless WEP) key forms random permutation of all 8-bit values uses that permutation to scramble input info processed a byte at a time Remained trade secret till . | Network Security Lecture 17 Presented by: Dr. Munam Ali Shah Summary of the Previous Lecture We discussed stream ciphers and its working We explored how stream ciphers are efficient when compared to block ciphers in terms of performance Some examples of stream ciphers such as RC4, RC5 and blowfish etc. were explored Summary of the previous Lecture Stream Cipher Properties some design considerations are: long period with no repetitions statistically random depends on large enough key large linear complexity use of highly non-linear boolean functions Ci = Mi XOR StreamKeyi 3 Criteria from Rueppel Stream Cipher Illustration Summary of the Previous Lecture (RC4) a proprietary cipher owned by RSA another Ron Rivest design, simple but effective variable key size (1-256 bytes) byte-oriented stream cipher widely used (web SSL/TLS, wireless WEP) key forms random permutation of all 8-bit values uses that permutation to scramble input info processed a byte at a time Remained trade secret till 1994 Part 2 (d) Asymmetric Key Cryptography Outlines of today’s lecture We will explore the need, features and characteristics of public key cryptography The working/function of a public key cryptography scheme will be discussed in detail RSA, as an example, will be explained Objectives You would be able to present an understanding of the public key cryptography. You would be able use and implement the RSA technique. Different names Public key cryptography Asymmetric key cryptography 2 key cryptography Presented by Diffie & Hallman (1976) New directions in cryptography 9 Why Public-Key Cryptography? Key distribution under symmetric encryption requires Two communicants already share a key The use of Key Distribution Center (KDC) Whitfield Diffie & Martin Hellman reasoned 2nd requirement neglected the essence of cryptography, . the ability to maintain total secrecy over your own communication how to verify a message comes intact from the claimed sender? Private-Key Cryptography .
