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???
08/18/07 15:59
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Msg Score: +1
 +1 Good Answer/Helpful		 #143396 - More on checksums
Responding to: ???'s previous message
Jan said:
Russ, I seem to recall such a case... ;-)

Jan's referring here to this thread from several months ago, where he demonstrated great skill and determination in reverse engineering a checksum algorithm from some raw data that I had provided.

Today I stumbled upon descriptions of two checksum algorithms, one called Adler-32 and the other called Fletcher's checksum. They caught my eye because they are very similar to the algorithm that Jan and I were working on earlier.

They are easier to calculate than a full-blown CRC, and supposedly better at detecting errors than a simple checksum. An academic-looking paper here compares the two and gives more references for anybody who's interested.

-- Russ


List of 32 messages in thread
TopicAuthorDate
CRC16 CCITT - What a challenge!            01/01/70 00:00      
   Have you seen this?            01/01/70 00:00      
      Of course!            01/01/70 00:00      
         Balance            01/01/70 00:00      
            I know, Russ,            01/01/70 00:00      
         Code? What code?            01/01/70 00:00      
            in the code library - look to the left column            01/01/70 00:00      
               Thanks! I missed that note in the first post.            01/01/70 00:00      
   I need a hint            01/01/70 00:00      
      write down the bits            01/01/70 00:00      
         Thanks for the hint            01/01/70 00:00      
            Your observations plus a comparison in C            01/01/70 00:00      
               The rest of the story ...            01/01/70 00:00      
                  Compilers, but Keil C51 8.09 for the stated 28~            01/01/70 00:00      
                  and this processes only a nibble, isn't it...            01/01/70 00:00      
                     No, it process the entire byte.            01/01/70 00:00      
                        now it\'s my pencil time...            01/01/70 00:00      
                           FYFI            01/01/70 00:00      
                              Clarification re: 8-bit optimized term            01/01/70 00:00      
                              on optimisation            01/01/70 00:00      
                                 Jan's optimization            01/01/70 00:00      
                                    Re: on optimization            01/01/70 00:00      
                                       Can you please be more specific?            01/01/70 00:00      
                                          More specifically ...            01/01/70 00:00      
            and what            01/01/70 00:00      
               More on checksums            01/01/70 00:00      
   No reason to hide the excreted code            01/01/70 00:00      
      Excreted code needs context like any other code            01/01/70 00:00      
   One More Comment            01/01/70 00:00      
      ... and a marginal remark ...            01/01/70 00:00      
         Init all ones frequently specified            01/01/70 00:00      
   18 cycles            01/01/70 00:00      

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