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Re: Inexpensive way to backup data

 Brendan wrote: 
> Tom Metro wrote: 
>> The trick with Amazon S3 is getting end-to-end encryption working (so 
>> the data stored at Amazon is encrypted - not just encrypted over the 
> I have had awesome luck with 
> Rsync over SSH... 

How does that address end-to-end encryption? 

Dan Ritter wrote: 
> If you encrypt file-by-file, you lose some metadata security but 
> gain some efficiency. 

True. But even file-by-file encryption throws out substantial bandwidth 
efficiencies normally provided by rsync. 

The problem is that you can have a 100 MB file (say a database) that 
only has a few bytes different from the last incremental backup, but due 
to the way encryption works, when rsync examines the post-encryption 
file to see what is different, it'll appear like a completely different 
random collection of bytes. 

One project that attempts to address this with rsync is rsyncrypto:

which tunes the encryption to operate on relatively small blocks of 
data, so when only a small portion of a file changes, rsync is still 
able to identify the portions that changed. This of course comes at some 
expense to the strength of the encryption. 

I've also yet to see a solution that provides rsync like efficiency, but 
doesn't require local storage of the encrypted data (or the need to 
reencrypt everything before determining what differences are present 
between the local and remote copies). 


Tom Metro 
Venture Logic, Newton, MA, USA 
"Enterprise solutions through open source." 
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