Short: MD5-based Random Number Generator (PPC+68k) Author: Rich Skrenta, Andreas R. Kleinert (port and sample program) Uploader: info@ar-kleinert.de Type: dev/c ************************************************************************* After becoming frustrated with the lack of a standalone, portable, decent random number generator, I decided to make one based on a cryptographic one-way hash function. I chose MD5 since it is fast and free source was readily available. More cryptographically secure hash functions are available (e.g. SHA-1), but for the purposes of a rand/random/erand48 replacement, MD5 should be more than sufficient. MD5 takes an arbitrary amount of input and yields a 16 byte hash. This RNG continually MD5's a 16 byte digest, and uses the bottom N bits as the random number yielded, where N is just large enough to include the largest random number desired. To yield a random number between 0 and r: create mask which has enough bits to include all of r (for example, if r is 100, mask would be 0x7F) do { digest = MD5(digest) number = digest & mask } while (number > r) The digest should be loaded and saved to a disk file between invocations of a program using the RNG. Random functions appear after the included MD5 code. Send comments to: skrenta@pbm.com (Rich Skrenta) ************************************************************************* The Amiga 68k/PPC version comes with both, makefiles for 68k and PPC, and test programs for both CPUs. A few changes had to be made for the Amiga port (#ifdef AMIGA) - and since this random number generator has a "brain", the most important change perhaps was, that the location of this brain now is "s:randseed". In case you want to run multiple copies of it, you'll perhaps like to choose a different (process-dependent) name. You also could fetch the "digest" from somewhere else (i.e. using a conventional random number generator). -- ARK, 30/May/2000 ============================= Archive contents ============================= Original Packed Ratio Date Time Name -------- ------- ----- --------- -------- ------------- 459 254 44.6% 30-May-00 15:49:28 +main.c 2082 1021 50.9% 30-May-00 15:45:04 +MD5Random.readme 13836 8982 35.0% 30-May-00 15:49:30 +random 9932 3577 63.9% 30-May-00 15:39:30 +random.c 34830 16782 51.8% 30-May-00 15:50:06 +random.elf 831 383 53.9% 30-May-00 15:48:06 +random.info 233 155 33.4% 30-May-00 15:36:06 +SCOPTIONS 234 118 49.5% 30-May-00 15:23:38 +smakefile 200 103 48.5% 30-May-00 15:45:28 +smakefile68k -------- ------- ----- --------- -------- 62637 31375 49.9% 31-May-100 18:45:22 9 files