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SubjectRe: CONFIG_RANDOM (compromise?)

I hate to add to this debate, since it appears to be getting nowhere
fast, but I think it's time for a brief review of the major arguments
against keeping /dev/random in the kernel, and why none of them are
really persuasive.

>>>>> "Martin" == Martin Dalecki <> writes:

Martin> 0.4% here 0.4% there and we will soon see a kernel which
Martin> doesn't fit anymore, even when compressed, onto a 3.5inch
Martin> disk :-).

This is smiley'd for our protection, of course, but it's still an
often-cited reason that /dev/random ought to be made optional: kernel
bloat. The argument is roughly that all of these little things we
want to keep in the kernel will eventually result in a 3.6mb
(compressed) kernel that can only boot on an UltraSparc with 512mb of
RAM. But it's just not so; some slopes are not slippery, and this is
one of them. The core kernel developers are already quite sensitive
to issues of unnecessary code inflation and guard against it as often
as possible. The argument that this 16kb addition will lead by a
natural progression to megabytes of worthless code just can't go
through, although it's a common rhetorical trope.

I find the "people on 386-16's will have to wait longer to compile"
argument unpersuasive as well. This isn't because I have anything
against the people who are forced to use low-end hardware for Linux;
it used to take me upwards of two hours to build kernels on a 486-33
with 4mb of RAM, and every new feature cost more in terms of time. (I
continued to build new kernels almost daily.) People who are using
such hardware are simply used to long builds. If it's going to take
overnight to make a kernel, a few extra minutes for the random
generator just won't hurt all that much by comparison. So I guess
that here I don't see the burden as being that great.

There's also an argument that the random number generator causes
unnecessary overhead for people who never use it, and should therefore
be made an option. However, I have not yet seen anyone post
benchmarks or any other form of statistic which might demonstrate that
such overhead exists. I think the burden of proof is on their
shoulders in this instance. I, at least, would certainly be
interested in seeing if there is measurable slowdown.

Finally, there are technical arguments designed to show that
/dev/random's functionality can be gotten via cheaper (in terms of
processor time, or some other measure) methods. I'm hardly
aware of all the technical issues at play when it comes to
cryptography, but Ted appears convinced that no cheaper method can be
found that won't weaken the security of using /dev/random. On this, I
just have to defer to authority. ;-)

I've probably missed some of the arguments that have come up in this
debate so far, but these strike me as the major ones. None of them
look good yet, although maybe benchmarks demonstrating real
performance hits could be promising. To those who have argued against
/dev/random, I don't mean to trivialize your positions; I only
intended to say why others might not be immediately won over. And in
any case, it looks like Ted and Linus are the ones to convince here,
and Linus (hallowed be his name) has remained silent on this issue.

Maybe this should be moved to linux-randomness (along with the Penguin

Dan Weiskopf | "It's easier to say `I love you' than `Yours sincerely', | I suppose." -- Elvis Costello, "Big Sister's Clothes"
Rorschach@EFNet.IRC | Department of Philosophy, Brown University.

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