Re: Subject: OT: LUKS encryption -- block by block, file by file, or "one big lump"

[rhkramer@gmail.com]

Thanks to all who replied -- two clarifications requested below:

On Wednesday, March 08, 2023 09:45:33 PM David Christensen wrote:
...
> A few years ago, I did a "bit rot" experiment.  

Thanks for doing that experiment!

...

> I wiped a disk, applied
> a partitioning scheme, created a partition, formatted the partition with
> LUKS (with default encryption), opened the LUKS container, created an
> ext4 filesystem, mounted the filesystem, and wrote a large file
> containing a predictable pattern.  I used hexdump(1) to find the
> encrypted blocks on disk that corresponded to the file.  I used dd(1) to
> write directly to the disk and change some portion of a block underlying
> the file.  I then viewed the file contents with standard userland tools
> (e.g. less(1)).  To my dismay, the tools could read the file without
> error and the file contents were corrupt!  

Just so I'm clear on that last sentence, what you're saying is that less was 
able to read the file (view the content) but the file / content was corrupt?

And, was it the entire file that was corrupt?

> I seem to recall that the
> number of damaged bytes was the same on disc and in the file.

Maybe that answered my question -- I guess that is saying that only a few 
bytes in the file were corrupt, and they were localized to one portion of the 
file?

Thanks!

-- 
rhk 

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