ch. 11 – cipher techniques
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Ch. 11 – Cipher Techniques
Dr. Wayne Summers
Department of Computer Science
Columbus State University
Summers_wayne@colstate.edu
http://csc.colstate.edu/summers
3Networks and Cryptography
Top four layers use end-to-end protocols (e.g. telnet) only requiring that intermediate hosts forward messages
Bottom three layers use point-to-point or link protocols (e.g. IP)
In end-to-end encryption, each host shares a cryptographic key with each destination
In link encryption, each host shares a cryptographic key with its neighbor(s).
Distinction useful for traffic analysis
4Secure E-mail: PEM
User enters e-mail using a User Agent (UA)
UA hands message to Message Transfer Agent (MTA)
MTA sends message to destination host via other MTAs
Attacker can read/modify/forge/delete e-mail at any of the intermediary MTAs
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