Arch Linux

aardwolf

Member

From: Belgium

Registered: 2005-07-23

Posts: 305

/dev/random entropy

Hey,

When I try to use /dev/random in a program, it turns out that, even though there is music playing (sound card active) and vareous internet based programs running (network active), still only pressing keys on the keyboard and moving the mouse actually adds entropy to /dev/random.

Is there a way to let it have more inputs? There are for example many precision measurements and timings on the CPU that are appearantly being used by some other random generators, doesn't /dev/random use any of those? And sound  + network?

freakcode

Member

From: São Paulo - Brazil

Registered: 2007-11-03

Posts: 410

Website

Re: /dev/random entropy

The Linux kernel generates entropy from keyboard timings, mouse movements, and IDE timings and makes the random character data available to other operating system processes through the special files /dev/random and /dev/urandom. This capability was introduced in Linux version 1.3.30.[1]

There are some Linux kernel patches allowing one to use more entropy sources.[2] the audio-entropyd project, which is included in some operating systems such as Fedora, allows audio data to be used as an entropy source.[3] In some systems, network interrupts can be used as an entropy source as well.[4]

On systems using the Linux kernel, programs needing significant amounts of random data from /dev/urandom cannot co-exist with programs reading little data from /dev/random, as /dev/urandom depletes /dev/random whenever it is being read.[5]

Source: http://en.wikipedia.org/wiki/Entropy_(computing)

Or if local entropy is not enough for you, there's always http://www.random.org/

Last edited by freakcode (2008-09-21 08:43:54)

G_Syme

Member

Registered: 2007-01-04

Posts: 83

Re: /dev/random entropy

Is there a way to let it have more inputs? There are for example many precision measurements and timings on the CPU that are appearantly being used by some other random generators, doesn't /dev/random use any of those? And sound  + network?

As for sound, you don't have to patch your kernel. Take a look at randomsound.
Also, AFAICT, /dev/random doesn't generate entropy by itself, but is just a pool for entropy which can be filled by other processes. At least randomsound seems to behave in that way.

Randomsound is also mentioned in a Linux.com article about gnoMint, a tool for managing certificate authorities.

---

The courageous enter dark caves alone.
The clever send in the courageous first.
The cleverest wait behind the clever.