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Re: IVs, summary of discussion
>CFB-64), the data rates are all the same for these modes. The only
>advantage to OFB is the option to precompute key stream, but on a
>single processor machine that may not be much of an advantage. Next,
Actually, my original reason for proposing the precomputed key stream
was to reduce encryption latency on bursty, delay sensitive traffic
like interactive telnet sessions. This would be an advantage on an
underpowered, single processor machine.
Hilarie Orman dissented, saying that the speed of encryption
algorithms like DES should not be an issue. After bumming lots of
cycles from my own DES code, I now pretty much agree with her -- DES
speed may still be an issue for high speed file transfers, but it's
not really a problem for interactive traffic, at least not on
reasonably modern machines.
But I wouldn't object to an option to support an OFB (or counter mode)
encryption mode for those situations where latency (not throughput) is
unusually critical.
Phil
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