usc-csci530-f08-l03

usc-csci530-f08-l03 - Copyright 1995-2008 Clifford Neuman -...

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Unformatted text preview: Copyright 1995-2008 Clifford Neuman - UNIVERSITY OF SOUTHERN CALIFORNIA - INFORMATION SCIENCES INSTITUTE USC CSci530 Computer Security Systems Lecture notes Fall 2008 Dr. Clifford Neuman University of Southern California Information Sciences Institute Copyright 1995-2008 Clifford Neuman - UNIVERSITY OF SOUTHERN CALIFORNIA - INFORMATION SCIENCES INSTITUTE Administration Assignment 1 on course web page http://ccss.usc.edu/530 Due 24 September 2008 Copyright 1995-2008 Clifford Neuman - UNIVERSITY OF SOUTHERN CALIFORNIA - INFORMATION SCIENCES INSTITUTE Administration Symantec Fellowship Fellowship for graduate students in computer security. http://www.symantec.com/about/careers/college/fellowship.jsp Application Deadline is December 12 I will provide recommendations for up to 4 students. Copyright 1995-2008 Clifford Neuman - UNIVERSITY OF SOUTHERN CALIFORNIA - INFORMATION SCIENCES INSTITUTE CSci530: Security Systems Lecture 3 September 12, 2008 Cryptography Continued Dr. Clifford Neuman University of Southern California Information Sciences Institute Copyright 1995-2008 Clifford Neuman - UNIVERSITY OF SOUTHERN CALIFORNIA - INFORMATION SCIENCES INSTITUTE Digital Signatures Provides data integrity Can it be done with symmetric systems? Verification requires shared key Doesnt provide non-repudiation Need proof of provenance Hash the data, encrypt with private key Verification uses public key to decrypt hash Provides non-repudiation But what does non-repudiation really mean? Copyright 1995-2008 Clifford Neuman - UNIVERSITY OF SOUTHERN CALIFORNIA - INFORMATION SCIENCES INSTITUTE Digital Signatures RSA can be used DSA: Digital Signature Algorithm Variant of ElGamal signature Adopted as part of DSS by NIST in 1994 Slower than RSA (but likely unimportant) NSA had a hand in its design (?!) Key size ranges from 512 to 1024 bits Royalty-free Copyright 1995-2008 Clifford Neuman - UNIVERSITY OF SOUTHERN CALIFORNIA - INFORMATION SCIENCES INSTITUTE Key Exchange Diffie-Hellman key exchange Choose large prime n, and generator g For any b in (1, n-1), there exists an a such that g a = b Alice, Bob select secret values x, y, resp Alice sends X = g x mod n Bob sends Y = g y mod n Both compute g xy mod n, a shared secret Can be used as keying material Copyright 1995-2008 Clifford Neuman - UNIVERSITY OF SOUTHERN CALIFORNIA - INFORMATION SCIENCES INSTITUTE Hash Functions Given m, compute H(m) Should be Efficient: H() easy to compute One-way: Given H(m), hard to find m such that H(m) = H(m) Collision-resistant: Hard to find m and m such that H(m) = H(m) Copyright 1995-2008 Clifford Neuman - UNIVERSITY OF SOUTHERN CALIFORNIA - INFORMATION SCIENCES INSTITUTE...
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usc-csci530-f08-l03 - Copyright 1995-2008 Clifford Neuman -...

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