*not on Linux!* The kernel provides real randomness (see urandom (4)). OK, it is pretty slow, but you can increase the data volume by using /dev/random as seed to a pseudo-random generator. Or, do cat /dev/random

myrandoms over night.

BTW, this is a good argument, why to use a Linux box in banking etc. enviornments running various hosts, because that is a quite unique feature of this O/S. Rainer Steffen Dettmer Sent by: suse-security-return-2595-rhoerbe=netpromote.co.at@suse.com 14.08.00 09:55 Please respond to "Steffen Dettmer" To: suse-security@suse.de cc: Subject: Re: [suse-security] password generator - Doh! * John Pinder wrote on Fri, Aug 11, 2000 at 02:03 -0700:

srand; sub randselect { $_[0]->[rand @{ $_[0] } ] } #Thank you O'Reilly!

mmm... If I see it right then you use rand as source of randomness only, ain't? This isn't always a nice idea, since the entrophy of rand may be low, and you have to note that i.e. a pid has usually only 16 bit (under some circumstances predictable) entrophy, and time() has a very few bits randomness only and should be predictable usually. It seems better for me, to use the tv.usec field returnd by gettimeofday() and/or collect some entrophy directly from the user. I made some programm that reads in keystrokes and uses the timeings between the keystrokes too. I used the following functions to collect entrophy. It's not really strong but obviously better than useing some time() get getpid() only. The value of "ps axww|gzip" should be a nice non-predictable thing too. I would be glad to get some comment about the following code, maybe I missed some important things? Here are the functions: sub keyboard_seed() { return 0 if ($NO_KEY_TYPEING); #do nothing if set #C would be better... ;-) my $time_sum=0; #"rotated" value for keystroke timings my $key_sum=0; #"rotated" value for keycodes my $rin=''; #select() bit vector vec($rin,fileno(STDIN),1) = 1; #construct STDIN select vector $r=$rin; #select-vector system "stty", '-icanon', '-echo', 'eol', "\001"; #set line discipline: non canonical mode no echo select(STDOUT); $|=1; #set STDOUT unbuffered print "I have to collect some enthropy. ", "I'll analyze you keyboard hits.\n"; print "Please hit 32 keys now: [", " " x 32, "]\n"; print " ---> "; for ($n=0; $n<32; $n++) { #32 keys my $one_time=0; #time between two keystrokes my $c=''; #1 byte input buffer while (($rin=$r,$nfound = select($rin, undef, undef, 0.01)) == 0) { #wait until data on STDIN $one_time++; #a time tick without data $one_time %= 2**8; #we take 4 bit only... } sysread(STDIN, $c, 1); #read char from STDIN print "*"; #just a mark #add some bits to sum: my $b4 = ((4 ** $n)%(2**16)); #max 2 bytes (factor) my $b6 = ((6 ** $n)%(2**16)); #max 2 bytes (factor) $time_sum = $time_sum + $one_time * $b4; #4 bits (a "shift" in) $key_sum = $key_sum + ( ord($c)-ord('0')) * $b6;#6 bits } print "\nENOUGH, Thank you!\n\n"; sleep 2; #now we have to flush input (for such users that type 33 chars :-) while (($rin=$r,$nfound = select($rin, undef, undef, 0)) != 0) { sysread(STDIN, $rin, 1); #trash input } #restore line discipline mode system "stty", 'icanon', 'echo', 'eol', '^@'; # ASCII null select(STDOUT); $|=0; #set line buffered mode my $seed = $time_sum ^ $key_sum ; #XOR timer and key longs printf " (Keyboard seed value: 0x%X [T:0x%X K:0x%X])\n", $seed, $time_sum, $key_sum unless($QUIET_MODE); return $seed; #pass seed to caller } sub rnd_init() { #calling srand with entrophy... #we "hash" some "ps" process info and collect enthropy from user open(OLDERR, ">&STDERR") or die "STDERR->OLDERR $!\n"; open(STDERR, ">/dev/null") or die "STDERR->/dev/null $!\n"; close(STDERR); #"redirect" STDERR; it seems that IT DOES NOT WORK CORRECTLY!! #$seed1 = (unpack "%L*", `find /proc -print | xargs cat gzip`); $seed1 = keyboard_seed(); $seed2 = (time ^ $$ ^ unpack "%L*", `ps axww | gzip`); $seed = $seed1 ^ $seed2; #next line DOES NOT WORK correctly at least under Solaris!!! open(STDERR, ">&OLDERR") or print OLDERR "OLDERR->STDERR $!\n"; close (OLDERR); printf " --> 32 bits enthropy: 0x%X <--\n", $seed unless ($QUIET_MODE); srand($seed); #set calculated seed } oki, Steffen -- Dieses Schreiben wurde maschinell erstellt, es trägt daher weder Unterschrift noch Siegel. --------------------------------------------------------------------- To unsubscribe, e-mail: suse-security-unsubscribe@suse.com For additional commands, e-mail: suse-security-help@suse.com