failed decryption

[Adam Gold]

On 4/19/2015 11:08, Pete Stephenson wrote:
> On Sun, Apr 19, 2015 at 11:21 AM, Mick Crane <mick.crane at gmail.com> wrote:

>> The problem with encrypting files for storage seems to be that if there is any corruption there is no way to get any of it back.
> 
> In such cases it might be worthwhile to use some sort of
> error-detection/correction system. Detecting errors is relatively
> straightforward (you can sign a message and if the signature fails,
> it's been modified) but correction is slightly more complex.
> 
> I generate PAR2 error-correction files[1] for important files or
> archives. It allows one to detect errors and repair/recover any
> damaged or lost sections up to a user-defined threshold. It uses more
> disk space, but it can be a life-saver when dealing with critical
> files on unreliable storage (and all storage is unreliable).
> 
> Alas, it's not retroactive and can't repair already-damaged data: you
> need to generate the PAR2 files when the original file is still
> undamaged and can then use it to recover damaged data later. In the
> case of sensitive data, one should encrypt the data first and then
> generate the PAR2 files -- that way no information about the encrypted
> content can leak.
> 
> Cheers!
> -Pete
> 
> [1] https://en.wikipedia.org/wiki/Parchive
> 
Thank you both for the feedback.  I guess I will have to put this down
as a rather painful learning exercise!  I will most certainly look into
PAR2 files for the future.