Table of Contents
CSE 589 -- Lecture 8
Plan for Today
Security Risks of Internet Communication
Terminology
The cast of characters
Encryption: Symmetric (private key) cryptography
Protocol for communicating using symmetric cryptography
Problems
Public key algorithms:
Protocol for communicating using public-key cryptography
Public-Key Cryptography
Idea: uses trapdoor one-way function.
One-Way Functions
Review of Number-theoretic Preliminaries
More NT Review:
More NT Review:
PPT Slide
RSA
Example
Issues
Why does it work? Encryption & decryption inverses
Implementing RSA
Probabilistic Primality Testing
Probabilistic Primality Testing
A few obvious questions….
Implementing RSA, cont.
Security of RSA
Factoring
A bit of factoring history...
Chosen Ciphertext Attack Against RSA: Scenario 1
Chosen Ciphertext Attack Against RSA: Scenario 2
What’s going on?
General Comments About Public-Key Cryptosystems
Hybrid Cryptosystems
PPT Slide
Digital Signatures
Digital Signatures
Signing Documents with Public Key Cryptography
Digital Signatures
Problem
Just to be completely clear… Using RSA...
Digital Signatures useful for
Digital Signatures + Encryption proof of authorship + privacy
Issues
PPT Slide
Problem with Signature Schemes
Another Problem
A solution: One-way hash functions.
Signatures and One-way Hash Functions
Issues and Attacks
Some One-Way Hash Functions
PPT Slide
Classic Secret Key Exchange Diffie-Hellman
Security Against Eve
Security Against Mallory Man-in-the-Middle Attack
What we want
Authenticated Key Exchange Private-Key Setting
Kerberos A key(T,A) B key(T,B) t timestamp K session key L lifetime
Authenticated Key Exchange-- Public-Key Setting
And then...
PPT Slide
So far
MAC
Some Applications of MACs
Constructing a MAC
PPT Slide
Secure Socket Layer (SSL) used by Navigator/Explorer...
SSL (Step 1)
SSL Step 2
SSL Step 3
SSL Step 4
SSL Step 5
Conclusions on Crypto
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