lecture11 - ECE 4514 Digital Design II Spring 2008 Hardware...

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Unformatted text preview: ECE 4514 Digital Design II Spring 2008 Hardware Implementation of Patrick Schaumont Spring 2008 ECE 4514 Digital Design II Lecture 11: Design of a SHA-1 module the SHA-1 Hashing Algorithm A Design Lecture Patrick Schaumont http://www.itl.nist.gov/fipspubs/fip180-1.htm This Lecture b Look at the implementation of a hashing algorithm in hardware b See the 'non-blocking assignment' in action b Study how the data-flow and operations of a complete algorithm are mapped into clock cycles and operators s Reuse of operators over clock cycles (operation multiplexing) Patrick Schaumont Spring 2008 ECE 4514 Digital Design II Lecture 11: Design of a SHA-1 module s Input-output operations over multiple clock cycles (io muxing) What does a hash do? b Provide a 'checksum' of a file of information b Used to verify the integrity of that information ata 16 Mbyte New York Stock Exchange ata 16 Mbyte London Stock Exchange Transmit Data + Hash Patrick Schaumont Spring 2008 ECE 4514 Digital Design II Lecture 11: Design of a SHA-1 module data hash 160 bits data hash 160 bits ==? Data is Correct ! What is a good hash function? b Standard Criteria: s Must deliver good compression, eg. 16MByte -> 160bits s Must be easy to compute b For integrity applications we also need: Patrick Schaumont Spring 2008 ECE 4514 Digital Design II Lecture 11: Design of a SHA-1 module s One-way : given the hash, you cannot find the orginial message s Weak Collision Resistance : For a given message and hash, it must be hard to find another message with the same hash s Strong Collision Resistance : It must be hard to find any two messages with the same hash Why a one-way hash? b Assume that Tracey, Carl and Carol are doing online bidding on a bulletin board. b They post their bid as a messages to the BB. b How can we keep their bid confidential while preventing cheating? Patrick Schaumont Spring 2008 ECE 4514 Digital Design II Lecture 11: Design of a SHA-1 module b Answer - They post a hash of their bid amount. This way, everyone is sure that everybody else has done a bid. After bids are posted, Tracey, Carl and Carol reveal their unhashed bid amount. The winning bid can now be selected, and verified by the others. What is the problem with collisions? b Tampered information may go undetected "Lower the rate by 0.5%" Bernanke emails the Fed Office: L o w e r t h e r a t e b y . 5 % xor ssume sum(xor) used Patrick Schaumont Spring 2008 ECE 4514 Digital Design II Lecture 11: Design of a SHA-1 module CHKSUM assume sum(xor) used to verify integrity What is the problem with collisions? b Tampered information may go undetected "Lower the rate by 0.5%" Bernanke emails the Fed Office: L o w e r t h e r a t e b y . 5 % xor ssume sum(xor) used Patrick Schaumont Spring 2008 ECE 4514 Digital Design II Lecture 11: Design of a SHA-1 module CHKSUM A clever (and aspiring criminal) investor intercepts the message and changes it .....
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This note was uploaded on 12/24/2011 for the course ECE 4514 taught by Professor Staff during the Fall '08 term at Virginia Tech.

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lecture11 - ECE 4514 Digital Design II Spring 2008 Hardware...

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