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

[Chris Wilson]

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?

Cheers, Chris.
-- 
_ ___ __     _
  / __/ / ,__(_)_  | Chris Wilson <0000 at qwirx.com> - Cambs UK |
/ (_/ ,\/ _/ /_ \ | Security/C/C++/Java/Perl/SQL/HTML Developer |
\ _/_/_/_//_/___/ | We are GNU-free your mind-and your software |