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Re: new second mandatory IPsec cipher
"Steven M. Bellovin" wrote:
>It's quite certain that we'll want to mandate AES once it's blessed. It
> isn't, and won't be for a while yet. What we do know is that it will use
> 16-byte blocks -- and that change is likely to upset some implementations;
> vendors may want to start testing that now -- and variable-length keys
> starting at 128 bits.
Howdy ()
16-byte blocks... ouch. Here's a little point to keep in mind: IP
fragments come in 8byte blocks. As long as your crypto cypher chuncks
though memory in 8 byte blocks, then your different fragments do not
have to be lined up contigously in memory. But pick a 16byte block
crypto tool and then you will have to get into memory copying fragments
around.
And I know that this is still a debate, but a good fraction of the
community here believe that if you are and SGW using IPSec selectors
which filter on ports, then you must do an 'intermediate reassemble' of
the packet even if you are not the end destianation. That could add up
to alot of traffic which a 16byte cypher would force you to mem-copy all
about.
Perhaps, given time, all us implementors could think up optimizations
which mitigate this problem, but why go there?
--
####################################
# Ricky Charlet
# (510) 795-6903
# rcharlet@redcreek.com
####################################
end Howdy;
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