+++ /dev/null
-/**
- * isaac - A fast, high-quality pseudo-random number generator.
- *
- * ISAAC (Indirect, Shift, Accumulate, Add, and Count) is the most advanced of
- * a series of pseudo-random number generators designed by Robert J. Jenkins
- * Jr. in 1996: http://www.burtleburtle.net/bob/rand/isaac.html
- * To quote:
- * No efficient method is known for deducing their internal states.
- * ISAAC requires an amortized 18.75 instructions to produce a 32-bit value.
- * There are no cycles in ISAAC shorter than 2**40 values.
- * The expected cycle length is 2**8295 values.
- * ...
- * ISAAC-64 generates a different sequence than ISAAC, but it uses the same
- * principles.
- * It uses 64-bit arithmetic.
- * It generates a 64-bit result every 19 instructions.
- * All cycles are at least 2**72 values, and the average cycle length is
- * 2**16583.
- * An additional, important comment from Bob Jenkins in 2006:
- * Seeding a random number generator is essentially the same problem as
- * encrypting the seed with a block cipher.
- * ISAAC should be initialized with the encryption of the seed by some
- * secure cipher.
- * I've provided a seeding routine in my implementations, which nobody has
- * broken so far, but I have less faith in that initialization routine than
- * I have in ISAAC.
- *
- * A number of attacks on ISAAC have been published.
- * [Pudo01] can recover the entire internal state and has expected running time
- * less than the square root of the number of states, or 2**4121 (4.67E+1240).
- * [Auma06] reveals a large set of weak states, consisting of those for which
- * the first value is repeated one or more times elsewhere in the state
- * vector.
- * These induce a bias in the output relative to the repeated value.
- * The seed values used as input below are scrambled before being used, so any
- * duplicates in them do not imply duplicates in the resulting internal state,
- * however the chances of some duplicate existing elsewhere in a random state
- * are just over 255/2**32, or merely 1 in 16 million.
- * Such states are, of course, much rarer in ISAAC-64.
- * It is not clear if an attacker can tell from just the output if ISAAC is in
- * a weak state, or deduce the full internal state in any case except that
- * where all or almost all of the entries in the state vector are identical.
- * @MISC{Pudo01,
- * author="Marina Pudovkina",
- * title="A Known Plaintext Attack on the {ISAAC} Keystream Generator",
- * howpublished="Cryptology ePrint Archive, Report 2001/049",
- * year=2001,
- * note="\url{http://eprint.iacr.org/2001/049}",
- * }
- * @MISC{Auma06,
- * author="Jean-Philippe Aumasson",
- * title="On the Pseudo-Random Generator {ISAAC}",
- * howpublished="Cryptology ePrint Archive, Report 2006/438",
- * year=2006,
- * note="\url{http://eprint.iacr.org/2006/438}",
- * }
- *
- * Even if one does not trust the security of this PRNG (and, without a good
- * source of entropy to seed it, one should not), ISAAC is an excellent source
- * of high-quality random numbers for Monte Carlo simulations, etc.
- * It is the fastest 32-bit generator among all of those that pass the
- * statistical tests in the recent survey
- * http://www.iro.umontreal.ca/~simardr/testu01/tu01.html, with the exception
- * of Marsa-LFIB4, and it is quite competitive on 64-bit archtectures.
- * Unlike Marsa-LFIB4 (and all other LFib generators), there are no linear
- * dependencies between successive values, and unlike many generators found in
- * libc implementations, there are no small periods in the least significant
- * bits, or seeds which lead to very small periods in general.
- *
- * Example:
- * #include <stdio.h>
- * #include <time.h>
- * #include <ccan/isaac/isaac.h>
- *
- * int main(void){
- * static const char *CHEESE[3]={"Cheddar","Provolone","Camembert"};
- * isaac_ctx isaac;
- * unsigned char seed[8];
- * time_t now;
- * int i;
- * //N.B.: time() is not a good source of entropy.
- * //Do not use it for cryptogrpahic purposes.
- * time(&now);
- * //Print it out so we can reproduce problems if needed.
- * printf("Seed: 0x%016llX\n",(long long)now);
- * //And convert the time to a byte array so that we can reproduce the same
- * // seed on platforms with different endianesses.
- * for(i=0;i<8;i++){
- * seed[i]=(unsigned char)(now&0xFF);
- * now>>=8;
- * }
- * isaac_init(&isaac,seed,8);
- * printf("0x%08lX\n",(long)isaac_next_uint32(&isaac));
- * printf("%s\n",CHEESE[isaac_next_uint(&isaac,3)]);
- * printf("%0.8G\n",isaac_next_float(&isaac));
- * printf("%0.8G\n",isaac_next_signed_float(&isaac));
- * printf("%0.18G\n",isaac_next_double(&isaac));
- * printf("%0.18G\n",isaac_next_signed_double(&isaac));
- * return 0;
- * }
- *
- * License: Public Domain
- */
-#include <string.h>
-#include <stdio.h>
-#include "config.h"
-
-int main(int _argc,const char *_argv[]){
- /*Expect exactly one argument.*/
- if(_argc!=2)return 1;
- if(strcmp(_argv[1],"depends")==0){
- printf("ccan/ilog\n");
- return 0;
- }
- return 1;
-}
projects / ccan / blobdiff