On Sun, 18 Feb 1996, Bruce Murphy wrote:
In message <199602172002.MAA09152@netcom20.netcom.com>, maruishi@netcom.com wrote:
I was trying to think of a way to come up with true random numbers... And knowing a bit of UNIX socket TCP/IP programming I made a small little program that generates random numbers by measuring the mili-second timing ies a TCP packet to bounce back, from another network. My program simply send some data to port 7 (echo port) of a network on an i nternal list. Then timing it, randomly picks a different network to send to.
Interesting idea. Trends may be externally visible, You would probably want to normalize it, and you would find that there was quite a few deterministic elements of network load -> delay.
Oh, did I mention clock granularity?
In short you really aren't going to get 'random numbers' from such a scheme, but that's not to say you couldn't have fun playing with it, you might even find some use for the ways of calculating immediate network load around a node. Especially with regard to interception of packets and allowing for time discrepancies whilst doing so.
Altogether off topic, but could maybe be developed into an idea with, maybe a 30% change of being Perrygrammed. Keep working.
<invisible to perry> Bounce me the code, could be interesting </invisible to perry>
-- Packrat (BSc/BE;COSO;Wombat Admin) Nihil illegitemi carborvndvm.
Here is the code. Its pretty quick and dirty. #include <sys/types.h> #include <sys/socket.h> #include <netinet/in.h> #include <stdio.h> #include <time.h> #include <netdb.h> #include <unistd.h> #include <sys/time.h> #include <time.h> #define NET_NUM 1/*change this to the number of networks in the list below******************************/ struct timezone tz; struct sockaddr_in addr; unsigned int bits; main(int argc, char **argv) { struct timeval tv; register FILE *fin, *key, *nets; int sock, c, dt, i, net; unsigned char *packet; unsigned char ch; if(argc != 3) { printf("Usage: %s [key.file.path] [number of bits in key]\n", argv[0]); exit(1); } if((key = fopen(argv[1], "wb")) == NULL) { perror("file open"); exit(1); } net = 1; packet = (unsigned char *)malloc(16);/*you can of course change this value*/ memset(packet, "X", 16); bits = atoi(argv[2]); bits = bits / 8; /*how many bytes?*/ for(i = 0; i<bits; i++) { sock = con(getn(net));/*Make a connection and return the socket.*/ if((fin = fdopen(sock, "r")) == NULL) { perror("fdopen"); close(sock); exit(1); } (void) gettimeofday(&tv, &tz); sendto(sock,packet, 16, 0, (struct sockaddr *) &addr,sizeof(struct sockaddr)); write(sock, "\r\n", 2); while ((c = getc(fin)) != '\n') ; dt = deltaT(&tv); close(sock); fclose(fin); ch = dt % 255; fputc(ch, key); net = dt % NET_NUM; }/*for*/ } int con(char *where) { struct sockaddr_in addr; struct hostent *host_; register FILE *fin, *fp; int sock, c, dt; char *packet; unsigned char ch; (void) bzero((char *)&addr, sizeof(struct sockaddr_in)); addr.sin_addr.s_addr = inet_addr(where); if((int)addr.sin_addr.s_addr == -1) { host_ = gethostbyname(where); if (host_ != NULL) bcopy(host_->h_addr, (char *)&addr.sin_addr, host_->h_length); else { printf("Host not found.\n"); exit(1); } } addr.sin_family = AF_INET; addr.sin_port = htons(7); sock = socket(AF_INET,SOCK_STREAM,IPPROTO_TCP); if (sock < 0) { fprintf(stderr,"error: socket() failed\n"); perror("socket"); return; } if(connect(sock, (struct sockaddr*) &addr, sizeof(addr))<0) { close(sock); fprintf(stderr, "socket connection error\n"); perror("connection"); exit(1); } return sock; } /**************put your network list down here************/ char *getn(int num) { char *nets[] = { "127.0.0.1" }; return nets[num]; } /*This part is taken from traceroute.*/ deltaT(tp) struct timeval *tp; { struct timeval tv; (void) gettimeofday(&tv, &tz); tvsub(&tv, tp); return (tv.tv_sec*1000 + (tv.tv_usec + 500)/1000); } tvsub(out, in) register struct timeval *out, *in; { if ((out->tv_usec -= in->tv_usec) < 0) { out->tv_sec--; out->tv_usec += 1000000; } out->tv_sec -= in->tv_sec; }