Re: entropy + openSSL question

From: Seth Arnold (sarnold@wirex.com)
Date: 02/19/03

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    Date: Wed, 19 Feb 2003 10:38:43 -0800
From: Seth Arnold <sarnold@wirex.com>
To: focus-linux@securityfocus.com

    On Tue, Feb 18, 2003 at 10:32:15PM -0300, Felix Cuello wrote:
    > Think about that... if you have enough entropy to do good keys, suppose
    > that not any longer than 1024 bits. Whatīs happened if you want to
    > generate a key with 2048 bits length when entropy is out?? Well, an
    > algorithm do the job to generate pseudorandom numbers. (In case that
    > /dev/random or /dev/urandom doesnīt stop, because I donīt remember now but
    > any of this devices stops when entropy is out)

    /dev/urandom on linux and openbsd will not block; they just print hashed
    versions of what is in the entropy pool. /dev/random on linux, and
    /dev/srandom on openbsd will block until entropy is available.

    > Then... I start again with my first question. thereīs a good way to
    > generate entropy??? [Suppose that the machine who generates the key will
    > not have much interrupts because anybody are in front of the keyboard to
    > generate it]

    Robert M Love has put together some patches for the Linux kernel to add
    network interfaces to the device drivers that generate entropy for the
    random pool: http://www.tech9.net/rml/linux/ Note that this is of
    debatable value; since network traffic may be seen or even controlled by
    attackers, it may or may not add real entropy to the pool. You need to
    decide for yourself if this is a concern.

    Cheers 

    -- 
Join the fight against terrorism by giving up your liberties today!

    Relevant Pages

    • Re: Random Number Help
      ... Linux, /dev/urandom: a PRNG. ... from the entropy pool which /dev/random uses; a root user may also add ... Linux distributions create a random seed after each boot, ...
      (sci.crypt)
    • Re: new /dev/random
      ... >> There is no blocking device in Linux, ... >> even after it already has enough entropy to provide security. ... In Linux, ... system events, which can take an extremely long time. ...
      (sci.crypt)
    • Re: /dev/random is probably not
      ... > Linux cited using keyboard interrupts. ... Twisting and stirring the bits should scatter entropy evenly in the pool. ...
      (Bugtraq)
    • Re: /dev/random is probably not
      ... >> Linux cited using keyboard interrupts. ... > Twisting and stirring the bits should scatter entropy evenly in the pool. ... This doesn't change the predictability. ...
      (Bugtraq)
    • Re: strengthening /dev/urandom
      ... The Linux /dev/random mixer has some general-purpose entropy estimation ... /dev/random is safe, if you want a true RNG (i.e., true entropy, secure ... against information-theoretic attacks) or if you don't trust the crypto. ...
      (sci.crypt)