On Thu, Oct 7, 2021 at 02:52:07PM -0400, Stephen Frost wrote: > > > Is there a particular reason why you would prefer not to use LSN? I > > > suggested > > > it because in my view having a variable tweak is still better than not > > > having > > > it even if we deem the risks of XTS tweak reuse not important for our use > > > case. > > > The comment was made under the assumption that requiring wal_log_hints for > > > encryption is acceptable. > > > > Well, using the LSN means we have to store the LSN unencrypted, and that > > means we have to carve out a 16-byte block on the page that is not > > encrypted. > > With XTS this isn't actually the case though, is it..? Part of the > point of XTS is that the last block doesn't have to be a full 16 bytes.
> What you're saying is true for XEX, but that's also why XEX isn't used > for FDE in a lot of cases, because disk sectors aren't typically > divisible by 16. Oh, I was not aware of that XTS feature. Nice. > https://en.wikipedia.org/wiki/Disk_encryption_theory > > Assuming that's correct, and I don't see any reason to doubt it, then > perhaps it would make sense to have the LSN be unencrypted and include > it in the tweak as that would limit the risk from re-use of the same > tweak over time. Yes, seems like a plan. -- Bruce Momjian <br...@momjian.us> https://momjian.us EDB https://enterprisedb.com If only the physical world exists, free will is an illusion.
