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Re: IPG algorithim
[email protected] wrote:
>
>
>
> Everything is still screwed up. The As, Bs and Cs are selected in much the
> same fashion as LOTTO numbers except that the pools are much larger and
> order is significant. They are not random, that would never work.
Maybe I missed something at your website, but... how exactly they
are selected? Where is it described?
igor
> On Sat, 30 Nov 1996, Eric Murray wrote:
>
> >
> > Igor Chudov @ home writes:
> > >
> > > [This is an addition to my previous reply to Eric]
> > >
> > > It bugs me that you are using rand() (a fairly lame pseudo-random
> > > function that was never intended to be used in cryptographic
> > > applications) to seed A, B, C and JV and then test the A(JV) for
> > > randomness. Some may object to that.
> >
> > Yea, you're right, rand() is lame.
> >
> > I added /dev/random to my Linux box and changed my small test to use it.
> > I also changed the way that I use JV- I had been setting it to a random
> > value for each trip through the "engine", but since I beleive that
> > its value can't really be random (if you want to be able to have someone
> > decrypt your stuff :-) but must be exchanged in the key, I set it
> > to a random value once and then let it float. It's also a lot faster
> > that way, /dev/random is pretty slow (because it's looking for real
> > random material).
> >
> > My results from xnoisesph were wrong- xnoisesph wants random bytes
> > instead of random integers in ascii format as I was producing.
> > Changing it (as I have below) makes the xnoisesph output look
> > much better, but it still isn't all that random. The random seed generators
> > I have written that get their randomness from repeated calls
> > to high-resolution timers and hashes of system log files do better.
> > I also fixed a minor bug in arg processing.
> >
> >
> >
> >
> >
> >
> > #include <stdio.h>
> > #include <fcntl.h>
> >
> > /* a C translation of the IPG "EUREKA" algorithim's "engine".
> > ** This is supposed to produce random numbers for the IPG
> > ** "encryptor stream".
> > ** See http://www.netprivacy.com/ for the original description.
> > ** Eric Murray [email protected] This code placed under GNU copyleft.
> > ** V0.2 */
> >
> > typedef unsigned char byte;
> > typedef unsigned short uint16;
> >
> >
> > /* tables: */
> > uint16 A[53];
> > uint16 B[53];
> > uint16 C[53];
> >
> >
> > #ifndef NO_DEV_RANDOM
> > uint16 getrand()
> > {
> > uint16 ret;
> > int fd = open("/dev/random",O_RDONLY);
> > if (fd <= 0) {
> > perror("/dev/random"); exit(-1);
> > }
> > read(fd,(unsigned char *)(&ret),sizeof(ret));
> > close(fd);
> > return(ret);
> > }
> > #else
> > /* do something appropriate for your OS here, rand() is lame. */
> > #define getrand rand
> > #endif
> >
> >
> > int init_table(uint16*table, uint16 min, uint16 max)
> > {
> > /* IPG specifies no algorithim for producing the "random"
> > ** initial values in the ABC tables, but it's obvious that
> > ** it requires a PRNG that's somehow seeded from the "key".
> > ** I've used /dev/random here, so there's no question that
> > ** I'm starting out with pretty good random values. */
> > int i;
> > int count, r;
> >
> > for(i = 0; i < 53; i++) {
> > table[i] = min + (getrand() % (max - min));
> > }
> > }
> >
> > main(int argc, char **argv)
> > {
> > uint16 jv;
> > int argcnt, i, n, count, diehard, nelem;
> >
> > diehard = 0;
> > argcnt = 1;
> > if (argc >= 2) {
> > if (strncmp(argv[argcnt],"-d",2) == 0) {
> > diehard++;
> > argcnt++;
> > }
> > }
> > if (argc > argcnt - 1 ) {
> > n = atoi(argv[argcnt]);
> > fprintf(stderr,"Generating %d values\n",n);
> > }
> > else {
> > n = 2000;
> > }
> >
> > /* seed tables: */
> > fprintf(stderr,"Seeding: A"); fflush(stderr);
> > init_table(A,0,65535);
> > fprintf(stderr," B"); fflush(stderr);
> > init_table(B,0,12227);
> > fprintf(stderr," C"); fflush(stderr);
> > init_table(C,16384,20361);
> > fprintf(stderr,"\n"); fflush(stderr);
> >
> > /* generate n values: */
> > /* jv is "random" (where's it seeded from?) */
> > jv = (uint16)(getrand() % 53);
> > for(; n > 0; n--) {
> >
> > /* count limits the number of traverses to 53^2 so we don't get stuck */
> > /* 2809 is actually too low per Chudov:
> > ** "For example, if ALL B == 1, A == 16385, and C == 20361, the
> > ** loop may need (20361-16385) passes to get to the < 16384 value."
> > */
> > for(count = 0; count < 2809; count++) {
> > jv++;
> > if (jv == 53) jv = 0;
> > A[jv] = (A[jv] + B[jv]) % C[jv];
> > if (A[jv] < 16384) break;
> > }
> > if (count == 2809) fprintf(stderr,"Oops.\n");
> > else {
> > if (!diehard) {
> > write(1,(unsigned char *)&A[jv],sizeof(uint16));
> > }
> > else {
> > /* print output in DIEHARD required format:
> > ** actually since we have 16-bit ints and DIEHARD
> > ** wants 32-bit ints, we print 20 per line instead of 10 */
> > if (nelem++ > 19) {printf("\n"); nelem = 0;}
> > printf("%4.4x",(unsigned int)A[jv]);
> > }
> > }
> > }
> > }
> > --
> > Eric Murray [email protected] [email protected] http://www.lne.com/ericm
> > PGP keyid:E03F65E5 fingerprint:50 B0 A2 4C 7D 86 FC 03 92 E8 AC E6 7E 27 29 AF
> >
>
- Igor.