Re: /dev/random in 2.4.6

[daw@mozart.cs.berkeley.edu (David Wagner)]

Steve Hill  wrote:
>Hmm...  Well, ATM I've kludged a fix by using /dev/urandom instead, but
>it's not ideal because it's being used to generate cryptographic keys, and
>urandom isn't cryptographically secure.

I think you may want to check again.  /dev/urandom *is* cryptographically
secure, and should be fine to use for generating crypto keys [1].

This seems to be a common point of confusion.


[1] Well, if SHA isn't secure, then /dev/urandom might not be any good.
    But if SHA isn't secure, then the rest of your crypto might not be
    any good either, so you might as well trust /dev/urandom.

    There *is* a subtle difference between the two.  When you want
    forward secrecy, /dev/urandom might be insufficient: If your machine
    is broken into, an attacker can learn the state of the pool, and
    then if you kick off the attacker without rebooting or refreshing
    the /dev/urandom pool, the attacker might be able to predict your
    crypto keys for some time after he's lost access to your machine.
    However, I would imagine that in many settings this may not be a
    major concern, and it is easily remedied by rebooting or by
    otherwise re-seeding the /dev/urandom pool.