On Mon, 2004-03-22 at 16:25, Jeff Waugh wrote:
> <quote who="Jamie Wilkinson">
> 
> > Does anyone know much about GPG's encryption ciphers, and how well they
> > recover from stream errors?
> 
> > If not, does anyone have any recommendations on where I can start looking?
> > A google on error recovery for each of the ciphers in gpg --version wasn't
> > very useful.
> 
> Isn't that because they're orthogonal features? Surely the right way to
> approach this is to ensure the redundancy of the encrypted data, not build
> it into the encryption mechanism... Once upon a time I asked about lossy
> encryption. :-)

Yes and no. Having backups of backups of backups etc is a nice idea, but
I'm positing that it's not sustainable since there's only a finite (but
probably unbounded) amount of storage space available in the world. This
is about recovering data from a damaged stream, probably for the same
reasons that you'd try to recover an XFS filesystem for example.

Anyway there's a bunch of ways you could write that data. CBC for
example would clobber all the data that was written after the error,
whilst ECB wouldn't (though you'd reduce your security somewhat).

I don't remember enough about it, but there are modes where a single bit
error will clobber your entire stream IIRC.

However, I can't answer Jaq's question -- I know practically nothing
about gpg. Another option might be to use the openssl command to do the
cipher, so you have control over the stream mode.

j.


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