[REBOL] Re: Notes on seeding 'random/seed (long)
From: moliad:aei:ca at: 20-Mar-2004 22:37
thanks for this thesis on the randomizing of rebol Alan!
another tidbit of information that wasn't obvious to realize!
-MAx
----- Original Message -----
From: "alan parman" <[reboler--programmer--net]>
To: <[rebol-list--rebol--com]>
Sent: Saturday, March 20, 2004 10:08 PM
Subject: [REBOL] Notes on seeding 'random/seed (long)
> Here are some things I found out will working on 'random/secure and
'random/seed that may be of help to others.
> I wanted to completely utilize the time provided by 'now/precise as the seed
for 'random/seed.
> (for some cryptography related scripts)
>
> (the following messages are from the escribe archives and console output is
from view 1.2.5.3.1
> >From an earlier question on using 'random Joel Neely wrote:
> Date: Thu, 22 Aug 2002 15:09:45
>
> "The documentation should state what types of values are acceptable
> as seeds. I believe that you need to restrict yourself to date!,
> time!, or integer! values for legitimate seeds."
>
> And Frank Sievertsen wrote:
> [REBOL] Re: True Random
> Date: Mon, 20 Aug 2001 00:09:35
>
> Try this:
> random/seed checksum form now/precise
>
> CU,
> Frank
>
> With Petr Krenzelok adding:
> Date: Mon, 20 Aug 2001 00:32:38
>
> you can even use checksum/secure ....
>
> -pekr-
>
> But please observe the following...
>
> It appears that 'random/seed seeded with time ('now/precise) only seeds to the
second! ...
> randomize-series: func [series][
> random/seed now/precise
> random/secure series
> ]
>
> >> loop 10 [print [now/precise randomize-series "12345"]]
> 15-Jan-2004/12:20:06.968-5:00 14532
> 15-Jan-2004/12:20:06.968-5:00 14532
> 15-Jan-2004/12:20:06.968-5:00 14532
> 15-Jan-2004/12:20:06.984-5:00 14532
> 15-Jan-2004/12:20:06.984-5:00 14532
> 15-Jan-2004/12:20:07-5:00 13524
> 15-Jan-2004/12:20:07-5:00 13524
> 15-Jan-2004/12:20:07.015-5:00 13524
> 15-Jan-2004/12:20:07.015-5:00 13524
> 15-Jan-2004/12:20:07.015-5:00 13524
>
> ... as you see the randomized string only changes with the second.
>
> Changing the time to an integer won't work ...
>
> >> loop 10 [print [now/precise to-integer now/time/precise]]
> 15-Jan-2004/12:13:32.953-5:00 44012
> 15-Jan-2004/12:13:32.968-5:00 44012
> 15-Jan-2004/12:13:32.968-5:00 44012
> 15-Jan-2004/12:13:32.968-5:00 44012
> 15-Jan-2004/12:13:32.984-5:00 44012
> 15-Jan-2004/12:13:32.984-5:00 44012
> 15-Jan-2004/12:13:33-5:00 44013
> 15-Jan-2004/12:13:33-5:00 44013
> 15-Jan-2004/12:13:33-5:00 44013
> 15-Jan-2004/12:13:33.015-5:00 44013
>
> ... as you can see that the integer changes only with the second.
>
> Also, note that I only changed the time (not the date) to integer, because ...
>
> >> to-integer now/precise
> ** Script Error: Invalid argument: 15-Jan-2004/12:30:15.734-5:00
> ** Where: to-integer
> ** Near: to integer! :value
>
> ... thus not using the date portion in the potential seed.
>
> You cannot use checksum/secure on the time because ...
>
> >> random/seed checksum/secure form now/precise
> == {=EEen|^E?^A"d=A6-=C2=EA/=CC^K^G=AC=D1=FD}
>
> ... and ...
>
> >> seed: checksum/secure form now/precise
> == #{70C9F0D1D65FD88B6093DF38FD972ABCA56724B3}
> >> random/seed seed
> == "<`$-p*=C9=DF=BCg=D8=B3_=D6=A5=F08=FD"=D1"
> >> random/seed seed
> == "g<_=F0"=DF=C9`=BCp=FD=D1=D6=A5*$8-=B3=D8"
> >> random/seed seed
> == "=A5`=BC=D1_-p$=D8=F0<=FD=D6=C98*"=B3=DFg"
>
> ... returns a value! Thus the "seed" given above is scrambled , but not passed
to random/seed as a seed.
> If "checksum/secure form now/precise" was providing a legitimate seed then the
follwing sequences would be identical ...
> >> seed: checksum/secure form now/precise
> == #{70C9F0D1D65FD88B6093DF38FD972ABCA56724B3}
> >> random/seed seed
> == ""*g`=D1<=A5=BC=F0=B3=D8$=C98=D6_-p=DF=FD"
> >> loop 5 [print random/secure "12345"]
> 53142
> 31254
> 32514
> 25143
> 32145
> >> random/seed seed
> == "*=FDg`=D6=D1=B3=DFp=C9-"$=A5=D8_8=BC=F0<"
> >> loop 5 [print random/secure "12345"]
> 32415
> 13524
> 15432
> 45231
> 43251
>
> .. but they are not the same.
>
> So, to use _all_ of the information provided by 'now/precise (all of
15-Jan-2004/12:34:16.437-5:00) as a seed to 'random/seed you must
> random/seed to-integer checksum/secure form now/precise
>
> Now we see all the behavior we expect ...
>
> >> seed: to-integer checksum/secure form now/precise
> == 1264002547
> >> random/seed seed
> >> loop 5 [print random/secure "12345"]
> 45213
> 41325
> 45321
> 35124
> 14523
> >> random/seed seed
> >> loop 5 [print random/secure "12345"]
> 45213
> 41325
> 45321
> 35124
> 14523
>
> Notice that there is nothing returned when providing the seed and that the two
sequences are identical.
>
> Other Observations:
>
> 'random/seed will take a date ...
>
> >> seed: now/date
> == 16-Jan-2004
> >> random/seed seed
> >>
>
> .. because nothing is returned.
>
> A 'binary is not a legitimate seed ...
>
> >> seed: to-binary 100
> == #{313030}
> >> random/seed seed
> == "010"
>
> ... because a value is returned.
>
> A 'time is a legitimate seed ...
>
> >> seed: now/time
> == 22:11:03
> >> random/seed seed
> >>
>
> ... but remember that it is good only to the second!
>
> So, you need to do two tests to determine if a seed is legitimate:
>
> 1) Nothing returned from 'random/seed your-seed
> 2) Identical random sequences produced when reseeding from the same seed.
>
> To conclude: apparently only dates, times, and integers are legitimate seeds,
> and one way to use all of a 'now (including both date and sub-second
precision) is to
> random/seed to-integer checksum/secure form now/precise
>
> Here's a handy function to reseed to sub-second precision ...
>
> randomize: func [
> {Reseed the random number generator using 'now/precise, or enter a date!
time! integer! argument.}
> seed [any-type!]
> ][
> random/seed either value? 'seed [seed][to-integer checksum/secure form
now/precise]
> ]
>
> As a bonus (as if this wasn't long enough already!) I have included my
gleanings from the archives about 'random in the following binary!. Just
decompress.
