[tahoe-dev] zfec: integrity checking of erasure-coded blocks (+ small bug)

James james at lab6.com
Sat Mar 31 14:06:13 UTC 2012


Hi,

I read in the README for zfec that...

  "... you also need to do integrity checking (such
  as with sha256sum) on the blocks that result from the erasure coding
  in *addition* to doing it on the file contents!"

... in order to help identify corrupted blocks. But then you have to
store a list of valid sha256sums. To protect this list, you could
encode it with zfec, but... well, that's a recursive descent into
madness.

Is there a solution here, or is there actually no problem and I'm
worrying over nothing?

Also, I think I found a bug in cmdline_zfec.py (v1.4.22). If you
specify the input file using an absolute pathname, the --output-dir
option is ignored. You could fix this by replacing the line:

args.prefix = args.inputfile.name

with

args.prefix = os.path.basename(args.inputfile.name)

(plus an import in the appropriate place)

Otherwise, zfec is awesome - good work! :)

Thanks,
James



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