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Network Security Lecture 5
Public Key Cryptography and messae authentication ,[object Object],[object Object],[object Object]
Information Integrity Problems ,[object Object],Insert new record for Darth’s salary of $1,000,000 Salary Database E D E
Information Integrity Problems ,[object Object],Masquerading as Alice “ Give Darth a $10,000 raise -- Alice” E
Information Integrity Problems ,[object Object],“ Open the front gate. -- Alice” E
Information Integrity Problems ,[object Object],[object Object],[object Object],[object Object],Public storage M M ´
Information Integrity Problems ,[object Object],[object Object],[object Object],Public storage M M
Message Digest  ,[object Object],[object Object],[object Object],[object Object],[object Object]
Message Digest ,[object Object],[object Object],[object Object],[object Object],[object Object],Message Error detection bits
Modification Detection Code: MDC ,[object Object],[object Object],[object Object],[object Object],[object Object],Public storage M ´ h( M ´ ) h compare h( M )
Message Authentication Code:MAC ,[object Object],[object Object],[object Object]
Message Authentication Code ,[object Object],[object Object],[object Object]
Solving Integrity Problems ,[object Object],[object Object],[object Object]
Preimage Attack ,[object Object],[object Object],Public storage M ´ h( M ´ ) h Same! h( M )
Preimage Attack ,[object Object],[object Object],“ I’ll find some combination of these so they can’t detect the difference!”
Collision Attack ,[object Object],[object Object],[object Object]
Collision Attack ,[object Object],[object Object],[object Object],[object Object],[object Object],“We like kittens” h( “We like kittens” ) “ Give Darth a $5000 raise”
Digests and Networks ,[object Object],[object Object],[object Object],[object Object],M  
Digests and Networks ,[object Object],[object Object],M   h( M    )
Message Authentication Codes ,[object Object],[object Object],[object Object]
Message Authentication Codes ,[object Object],[object Object],[object Object],[object Object],M h ( M ,  k ) h ( M ,  k ) M h k h ( M ,  k ) compare “ If they match, then sender must have same key  k  as I do”
Authentication and Confidentiality ,[object Object],[object Object],[object Object],[object Object],h h h h h h h
Prefix/Postfix MAC ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Message
Nested MAC ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]
Chained MAC (CMAC) ,[object Object],[object Object]
Chained MAC (CMAC) ,[object Object],[object Object],[object Object],[object Object],[object Object]
Chained MAC (CMAC) ,[object Object],[object Object],[object Object],[object Object]
Chained MAC (CMAC) ,[object Object],[object Object],[object Object],[object Object]
Chained MAC (CMAC) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]
Compression Functions ,[object Object],[object Object],[object Object],[object Object],[object Object],f Message of arbitrary size m -bit digest
Compression Functions ,[object Object],[object Object],f k -bit message m -bit digest
Iterated Hash Function Merkle-Damgard scheme If the compression function in Merkle-Damgard scheme is collision resistant, the Hash function is also collision resistant
Iterated Hash Function ,[object Object],[object Object],[object Object],[object Object],[object Object],f n -bit message block  M  i   m -bit digest  H  i m -bit digest  H  i-1
Types of Hash Algorithms ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]
Block Ciphers for Hashing  ,[object Object],[object Object],[object Object],[object Object],[object Object]
Block Ciphers for Hashing  ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

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Network Security Lec5

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