Re: Question about removal, addition of data midfile

[Shachar S. <sh...@sh...>]

Ted Carnahan wrote:

> I understand that the rsync algorithm is capable of dealing with (for 
> example) insertions of data in mid-file, so that only the new data is 
> transferred even if the new data does not align with the algorithm's 
> block size.
>
> Does rsyncrypto do something similar?
Yes.
>   I was under the impression that the block size was fixed,
Depends on which block you are talking about. The encryption uses fixed 
size blocks (in AES's case, 8 bytes).
> so if a non-block-aligned chunk of data is inserted or removed 
> mid-file, rsyncrypto doesn't compensate for that.
No, that is not the case. If rsyncrypto detects that the change was in 
increments of partial block, then a non-complete block is encrypted 
(i.e. - the data is padded until it is 8 bytes long, and encrypted like 
that). As far as changes are concerned, rsyncrypto supports changes on 1 
byte boundaries.
>   Thus the data before the insertion is transferred efficiently, but 
> after the insertion the newly non-aligned data is transferred in full.
Again, that is not the case.
>
> Thanks for your clarification,
>
> Ted Carnahan
Shachar