From: Francis Cianfrocca Date: 2007-03-30T12:30:42+09:00 Subject: Re: Simple question on random numbers ------=_Part_42947_21375256.1175225440615 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Content-Disposition: inline On 3/29/07, Phillip Gawlowski wrote: > > > In which situation is the difference important? > My guess is, that it is cryptography, to make a salt in a key less > "guessable". Cryptography depends *critically* on high-quality ("real") randomness in a variety of areas. Without it you have no crypto! Last, but not least: Where would I go to create real random numbers, > preferably in a platform-independent way? I'm sure someone will disagree with this but real randomness generally requires exposure to a physical process of some kind. Things like thermal noise inside a processor chip, disk drive seek times, or the interpacket times on a network link. (Or the traditional standby, typing or moving a mouse at random.) On many Linux platforms, you can get a limited amount of good-quality noise by reading /dev/random, if it's implemented on your particular hardware. (/dev/urandom does not block but does not guarantee high entropy, and is not suitable for crypto.) Be careful if you use it for more than a few thousand bytes a minute. It can and will block. For a good long time, too. It that happens to you, you can generate noise at a somewhat higher rate by continually reading and writing very large disk files (taking care that the drive hardware and not the driver cache is getting exercised). Platform-independent: forget about it. ------=_Part_42947_21375256.1175225440615--