[squeak-dev] Re: Reed Solomon Blues
Robert Withers
robert.w.withers at gmail.com
Mon Dec 7 12:38:03 UTC 2015
Sorry, forgot to mentionthe test I am using is
CryptoReedSolomonTest>>#testEncodeAndDecodeRS_15_9. The other 2
encodeAnd Decode tests have teh wrong sized data at the level they are
testing. This data needs to be the size of an interleaved block of 4
chunks that fit the algorithm.
Just to inform you, in RS(9)(15) ,the data block is 4 times 9 nibbles or
36 nibbles/18 bytes. Foir some reason I am adding 4 bytes of lenght in
there, I think to differentiate use of different sized RS algorithms.
Robert
On 12/07/2015 07:20 AM, Robert Withers wrote:
> Hi Good morning,
>
> I am trying to port java code implementing Reed-Solomon encoding with
> a GaloisField and polynomial system. I am currently testing the
> easiest Mode, which is 9 data symbols, 15 code symbols and 3 symbols
> of error. Theer's 2 nibbles to a byte, so a split and join is needed.
> This all has to do with iteration where the base indexing changes from
> 0 to 1. I screwed it up in there somewhere and I am struggling to find
> teh issue. It looks like a complete code review...
>
> Since this is core crypto code, it would be an extra blessing if
> someone else's eyes were on this code in detail.More tests always help
> too. Would someone be willing to crawl into the java and squeak code
> to review, learn and qualify/validate? Also, you would be helping me
> understand all this polynomial math and where my indexing issue may be.
>
> The failure in Squeak is in the GenericGFPoly>>#divide: method. It
> runs forever and the quotient/remainder never reduces it's degree. So
> one of teh math operations is broken & failing. You can run the
> EncodingTests
>
> I am including a zip of the Java classes I use. This core Reed-Solomon
> code was written at Google and released open-source. I wrote a test
> and they pass, so code is working. The latest Cryptography package in
> the crypto repo is version 48. Please load that and run the
> CryptoReedSolomonTest to see the infiniteLoop of the polynomial divide.
>
> Let me know if you can help.
>
> Thanks,
> Robert
>
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