======Synopsis:======
[[set]] random_source [<0|1|2|3>]

======Description:======
The [[rand]]om function generates random numbers.  But what is a random
number?  A random number generator is often measured by 3 attributes

| Entropy | Given a set of the last <N> random numbers, how likely is it you can guess the next random number? (High entropy means less guessability) |
| Distribution | Given a set of the last <N> random numbers, how likely is it each of the possible values of <N> have appeared the same number of times? (High distribution means every value is hit the same number of times) |
| Repeatability | Given a set of the first <N> random numbers, how likely is it that you can create the same <N> random numbers again? (High repeatability means you can regenerate the same sequence upon request) |

A discussion of the pros and cons of each of these attributes is beyond
the scope of this document.  But the client has 4 random number generators:

^ Value ^ Description ^ Entropy ^ Distribution ^ Repeatability ^
| 0 | Reads from /dev/urandom | High | Medium | No |
| 1 | Traditional ircII PRNG | Low | High | Yes |
| 2 | gettimeofday() calls | Medium | Low | No |
| 3 | arc4random PRNG | High | Medium | No |

The factory default value is 0.  Although you can [[set]] the value to 
other than 0, 1, 2, or 3, any other values are treated as though you had
set it to 3.  If /dev/urandom is not available, then 0 behaves as though
you had set it to 1.

The random number generator is used by [[rand]] and [[randread]]

======History:======
The [[set random_source]] variable first appeared in EPIC4pre2.001-NR13.
Arc4random support (set random_source 3) first appeared in EPIC4-1.1.8.

#$EPIC: set_random_source.txt,v 1.5 2006/09/19 03:45:37 jnelson Exp $