RFC: end-to-end compare -aq (Was: Re: [Box Backup] Win32 native client service bbackupd.conf)

[Ben Summers]

On 3 Jul 2006, at 23:25, Chris Wilson wrote:

> Hi all,
>
> Please forgive me for jumping in late, and for asking what is  
> probably a stupid question, but here goes:
>
> Would it make sense for the client to download, from the server, a  
> list of blocks where the information supplied about each block is  
> (1) the IV used previously by the client to encrypt that block, and  
> (2) the current checksum on disk (on the server) of that block,  
> freshly computed by the server?
>
> Would that be enough to allow the client to re-encrypt the block  
> using the same IV, rather than a new IV, compute the checksum of  
> the block, and thus determine whether its local copy was different  
> to the one on the server? Unless of course some strange disk/memory  
> corruption on the server or client just happened to result in the  
> different encrypted block having the same checksum?


Yes, I think that would do the trick nicely.

It doesn't require the server to be trusted any more than the minimal  
"store files and let us retrieve them intact" requirement.

Ben