The patch below adds support for arc4random(), cryptographically secure
suite of functions, found commonly on *BSD and other OSes. The advantage
over using /dev/random is that we avoid talking with VFS and opening
file descriptor. Also, there is a arc4random_uniform() functions that
provides uniformly distributed number, as opposed to commonly used idiom
"rand() % foo".

This was developed and tested on OpenBSD with oRTP 0.22.

--- configure.ac.orig	Mon Nov 25 12:57:48 2013
+++ configure.ac	Mon Nov 25 12:59:26 2013
@@ -160,6 +160,9 @@ build_scheduler=yes
 dnl Check if we have seteuid system call
 AC_CHECK_FUNCS(seteuid)
 
+dnl Check if we have arc4random family routines available
+AC_CHECK_FUNCS(arc4random)
+
 
 dnl check if we can use the pthread_library
 AC_CHECK_LIB(pthread, pthread_mutex_init, [pthread_enabled=yes], [pthread_enabled=no])
--- src/netsim.c.orig	Mon Nov 25 13:16:42 2013
+++ src/netsim.c	Mon Nov 25 13:19:26 2013
@@ -110,7 +110,13 @@ static mblk_t *simulate_bandwidth_limit(RtpSession *se
 }
 
 static mblk_t *simulate_loss_rate(RtpSession *session, mblk_t *input, int rate){
-	if((rand() % 101) >= rate) {
+	int rrate;
+#ifdef HAVE_ARC4RANDOM
+	rrate = arc4random_uniform(101);
+#else
+	rrate = rand() % 101;
+#endif
+	if(rrate >= rate) {
 		return input;
 	}
 	freemsg(input);
--- src/ortp.c.orig	Mon Nov 25 12:54:51 2013
+++ src/ortp.c	Mon Nov 25 12:55:19 2013
@@ -49,9 +49,11 @@ RtpScheduler *__ortp_scheduler;
 extern void av_profile_init(RtpProfile *profile);
 
 static void init_random_number_generator(){
+#ifndef HAVE_ARC4RANDOM
 	struct timeval t;
 	gettimeofday(&t,NULL);
 	srandom(t.tv_usec+t.tv_sec);
+#endif
 }
 
 
--- src/rtpsession.c.orig	Mon Nov 25 13:15:47 2013
+++ src/rtpsession.c	Mon Nov 25 13:16:26 2013
@@ -98,7 +98,11 @@ extern void rtp_parse(RtpSession *session, mblk_t *mp,
 
 
 static uint32_t uint32_t_random(){
+#ifdef HAVE_ARC4RANDOM
+	return arc4random();
+#else
 	return random();
+#endif
 }
 
 
--- src/rtpsession_inet.c.orig	Mon Nov 25 13:09:20 2013
+++ src/rtpsession_inet.c	Mon Nov 25 13:14:50 2013
@@ -23,7 +23,7 @@
 #if defined(WIN32) || defined(_WIN32_WCE)
 #include "ortp-config-win32.h"
 #elif HAVE_CONFIG_H
-#include "ortp-config.h" /*needed for HAVE_SYS_UIO_H */
+#include "ortp-config.h" /*needed for HAVE_SYS_UIO_H and HAVE_ARC4RANDOM */
 #endif
 #include "ortp/ortp.h"
 #include "utils.h"
@@ -272,11 +272,16 @@ static ortp_socket_t create_and_bind_random(const char
 	for (retry=0;retry<100;retry++)
 	{
 		int localport;
+#ifdef HAVE_ARC4RANDOM
+		localport = 5000 + (int)arc4random_uniform(0x10000 - 5000);
+		localport &= 0xfffe;
+#else
 		do
 		{
 			localport = (rand () + 5000) & 0xfffe;
 		}
 		while ((localport < 5000) || (localport > 0xffff));
+#endif
 		/*do not set REUSEADDR in case of random allocation */
 		sock = create_and_bind(localip, localport, sock_family,FALSE);
 		if (sock!=-1) {
--- src/stun.c.orig	Mon Nov 25 12:44:52 2013
+++ src/stun.c	Mon Nov 25 12:57:12 2013
@@ -1159,6 +1159,9 @@ stunEncodeMessage( const StunMessage *msg, 
 int 
 stunRand(void)
 {
+#if defined(HAVE_ARC4RANDOM) 
+   return (int)arc4random();
+#else
    /* return 32 bits of random stuff */
    /* assert( sizeof(int) == 4 ); */
    static bool_t init=FALSE;
@@ -1251,6 +1254,7 @@ stunRand(void)
 #else
    return random(); 
 #endif
+#endif    /* HAVE_ARC4RANDOM */
 }
 
 
@@ -1260,10 +1264,15 @@ randomPort()
 {
    int min=0x4000;
    int max=0x7FFF;
-	
-   int ret = stunRand();
+   int ret;
+
+#ifdef HAVE_ARC4RANDOM
+   ret = min + (int)arc4random_uniform(max - min);
+#else
+   ret = stunRand();
    ret = ret|min;
    ret = ret&max;
+#endif
 	
    return ret;
 }
--- src/zrtp.c.orig	Mon Nov 25 13:20:20 2013
+++ src/zrtp.c	Mon Nov 25 13:25:41 2013
@@ -771,7 +771,11 @@ static OrtpZrtpContext* createUserData(ZrtpContext *co
 	userData->zrtpContext=context;
 	userData->timerWillTriggerAt=0;
 	userData->last_recv_zrtp_seq_number=0;
+#ifdef HAVE_ARC4RANDOM
+	userData->last_sent_zrtp_seq_number=arc4random_uniform(0xfffe) + 1;
+#else
 	userData->last_sent_zrtp_seq_number=rand()+1; // INT_MAX+1 (signed)
+#endif
 
 	userData->srtpRecv=NULL;
 	userData->srtpSend=NULL;