On Wed, 10 Oct 2001, Zlatin Balevsky wrote: > I remember long time ago (1993) there was a > compression program that had the feature of adding a > special checksum which was 2-5% of the size of the > file and then could restore a rather significan number > of missing or corrupt segments. > sounds like FEC to me.
> I remember personally zeroing out 100 disk sectors of > a file and the checksumming algorithm restored them > without trouble, and the checksum size was half that. > This is flatly impossible. If the redundancy at the end of the file is less than 100 sectors, there's no way it can recover 100 sectors of information. Just from an information theoretic standpoint. You can't have enough information to recover 100 sectors of arbitrary bits unless you have *at least* 100 sectors of redundant data. > I'm not talking about basic Hemming code here of > course, and even though they claimed it to be some > sort of interleaved XOR checksumming I'm sure it must > have been something more complex. > > If there is interest from the developers I can > research the topic further. > I'm sensing snake oil, but would like to know more. Thelema -- E-mail: thelema314 at bigfoot.com If you love something, set it free. GPG 1536g/B9C5D1F7 fpr:075A A3F7 F70B 1397 345D A67E 70AA 820B A806 F95D -------------- next part -------------- A non-text attachment was scrubbed... Name: not available Type: application/pgp-signature Size: 232 bytes Desc: not available URL: <https://emu.freenetproject.org/pipermail/devl/attachments/20011010/30d20f12/attachment.pgp>
