# lec-02 - CSE565 Computer Security Lecture 2 Basic...

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1 9/03/09 UB Fall 2009 CSE565: S. Upadhyaya Lec 2.1 CSE565: Computer Security Lecture 2 Basic Encryption & Decryption Shambhu Upadhyaya Computer Science & Eng. University at Buffalo Buffalo, New York, 14260 9/03/09 UB Fall 2009 CSE565: S. Upadhyaya Lec 2.2 Overview Lecture 2 Overview Terminology (5 minutes) Encryption by Substitutions & Transpositions (45 minutes)

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2 9/03/09 UB Fall 2009 CSE565: S. Upadhyaya Lec 2.3 Announcements Recitation for next week Properties of Arithmetic Inverses Divisors Prime Numbers Greatest Common Divisor Recitation for the following week Modular arithmetic Basic properties Operations 9/03/09 UB Fall 2009 CSE565: S. Upadhyaya Lec 2.4 Terminology Encryption A process of encoding a message Decryption It is the reverse process Encryption Algorithms A key K is generally used Symmetric encryption: Asymmetric encryption: )) , ( , ( P K E K D P = )) , ( , ( P K E K D P E D = Plaintext P=(p1,p2, …pn) Ciphertext Original Plaintext Encryption Decryption C=(c1,c2, … cm) C=E(P) P=D(C) =D(E(P))
3 9/03/09 UB Fall 2009 CSE565: S. Upadhyaya Lec 2.5 Cryptography & Cryptanalysis Cryptography Hidden writing -- encryption to conceal text Cryptanalysis Break an encryption Attempt to break a single message Attempt to recognize patterns in encrypted messages Attempt to find general weaknesses Breakable Encryption

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lec-02 - CSE565 Computer Security Lecture 2 Basic...

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