diff --git a/auto_tests/TCP_test.c b/auto_tests/TCP_test.c
index 686419a680..144d7e142b 100644
--- a/auto_tests/TCP_test.c
+++ b/auto_tests/TCP_test.c
@@ -17,6 +17,7 @@
 #include "../toxcore/TCP_client.h"
 #include "../toxcore/TCP_server.h"
 
+#include "../toxcore/crypto_core.h"
 #include "../toxcore/util.h"
 
 #include "helpers.h"
@@ -59,7 +60,7 @@ START_TEST(test_basic)
     Socket sock = net_socket(TOX_AF_INET6, TOX_SOCK_STREAM, TOX_PROTO_TCP);
     IP_Port ip_port_loopback;
     ip_port_loopback.ip = get_loopback();
-    ip_port_loopback.port = net_htons(ports[rand() % NUM_PORTS]);
+    ip_port_loopback.port = net_htons(ports[random_u32() % NUM_PORTS]);
 
     int ret = net_connect(sock, ip_port_loopback);
     ck_assert_msg(ret == 0, "Failed to connect to TCP relay server");
@@ -158,7 +159,7 @@ static struct sec_TCP_con *new_TCP_con(TCP_Server *tcp_s)
 
     IP_Port ip_port_loopback;
     ip_port_loopback.ip = get_loopback();
-    ip_port_loopback.port = net_htons(ports[rand() % NUM_PORTS]);
+    ip_port_loopback.port = net_htons(ports[random_u32() % NUM_PORTS]);
 
     int ret = net_connect(sock, ip_port_loopback);
     ck_assert_msg(ret == 0, "Failed to connect to TCP relay server");
@@ -423,7 +424,7 @@ START_TEST(test_client)
     crypto_new_keypair(f_public_key, f_secret_key);
     IP_Port ip_port_tcp_s;
 
-    ip_port_tcp_s.port = net_htons(ports[rand() % NUM_PORTS]);
+    ip_port_tcp_s.port = net_htons(ports[random_u32() % NUM_PORTS]);
     ip_port_tcp_s.ip = get_loopback();
     TCP_Client_Connection *conn = new_TCP_connection(ip_port_tcp_s, self_public_key, f_public_key, f_secret_key, nullptr);
     c_sleep(50);
@@ -452,7 +453,7 @@ START_TEST(test_client)
     uint8_t f2_public_key[CRYPTO_PUBLIC_KEY_SIZE];
     uint8_t f2_secret_key[CRYPTO_SECRET_KEY_SIZE];
     crypto_new_keypair(f2_public_key, f2_secret_key);
-    ip_port_tcp_s.port = net_htons(ports[rand() % NUM_PORTS]);
+    ip_port_tcp_s.port = net_htons(ports[random_u32() % NUM_PORTS]);
     TCP_Client_Connection *conn2 = new_TCP_connection(
                                        ip_port_tcp_s, self_public_key, f2_public_key, f2_secret_key, nullptr);
     routing_response_handler(conn, response_callback, (char *)conn + 2);
@@ -521,7 +522,7 @@ START_TEST(test_client_invalid)
     crypto_new_keypair(f_public_key, f_secret_key);
     IP_Port ip_port_tcp_s;
 
-    ip_port_tcp_s.port = net_htons(ports[rand() % NUM_PORTS]);
+    ip_port_tcp_s.port = net_htons(ports[random_u32() % NUM_PORTS]);
     ip_port_tcp_s.ip = get_loopback();
     TCP_Client_Connection *conn = new_TCP_connection(ip_port_tcp_s, self_public_key, f_public_key, f_secret_key, nullptr);
     c_sleep(50);
@@ -589,7 +590,7 @@ START_TEST(test_tcp_connection)
 
     IP_Port ip_port_tcp_s;
 
-    ip_port_tcp_s.port = net_htons(ports[rand() % NUM_PORTS]);
+    ip_port_tcp_s.port = net_htons(ports[random_u32() % NUM_PORTS]);
     ip_port_tcp_s.ip = get_loopback();
 
     int connection = new_tcp_connection_to(tc_1, tcp_connections_public_key(tc_2), 123);
@@ -597,7 +598,7 @@ START_TEST(test_tcp_connection)
     ck_assert_msg(add_tcp_relay_connection(tc_1, connection, ip_port_tcp_s, tcp_server_public_key(tcp_s)) == 0,
                   "Could not add tcp relay to connection\n");
 
-    ip_port_tcp_s.port = net_htons(ports[rand() % NUM_PORTS]);
+    ip_port_tcp_s.port = net_htons(ports[random_u32() % NUM_PORTS]);
     connection = new_tcp_connection_to(tc_2, tcp_connections_public_key(tc_1), 123);
     ck_assert_msg(connection == 0, "Connection id wrong");
     ck_assert_msg(add_tcp_relay_connection(tc_2, connection, ip_port_tcp_s, tcp_server_public_key(tcp_s)) == 0,
@@ -697,7 +698,7 @@ START_TEST(test_tcp_connection2)
 
     IP_Port ip_port_tcp_s;
 
-    ip_port_tcp_s.port = net_htons(ports[rand() % NUM_PORTS]);
+    ip_port_tcp_s.port = net_htons(ports[random_u32() % NUM_PORTS]);
     ip_port_tcp_s.ip = get_loopback();
 
     int connection = new_tcp_connection_to(tc_1, tcp_connections_public_key(tc_2), 123);
diff --git a/auto_tests/conference_test.c b/auto_tests/conference_test.c
index 9e784e857d..9f8352a3b5 100644
--- a/auto_tests/conference_test.c
+++ b/auto_tests/conference_test.c
@@ -15,6 +15,7 @@
 #include <stdlib.h>
 #include <time.h>
 
+#include "../toxcore/crypto_core.h"
 #include "../toxcore/tox.h"
 #include "../toxcore/util.h"
 
@@ -209,7 +210,7 @@ static void test_many_group(void)
     TOX_ERR_CONFERENCE_SEND_MESSAGE err;
     ck_assert_msg(
         tox_conference_send_message(
-            toxes[rand() % NUM_GROUP_TOX], 0, TOX_MESSAGE_TYPE_NORMAL, (const uint8_t *)GROUP_MESSAGE,
+            toxes[random_u32() % NUM_GROUP_TOX], 0, TOX_MESSAGE_TYPE_NORMAL, (const uint8_t *)GROUP_MESSAGE,
             sizeof(GROUP_MESSAGE) - 1, &err) != 0, "Failed to send group message.");
     ck_assert_msg(
         err == TOX_ERR_CONFERENCE_SEND_MESSAGE_OK, "Failed to send group message.");
diff --git a/auto_tests/crypto_test.c b/auto_tests/crypto_test.c
index 3b95dcc12f..23c45dd0bf 100644
--- a/auto_tests/crypto_test.c
+++ b/auto_tests/crypto_test.c
@@ -12,6 +12,7 @@
 
 #include "helpers.h"
 
+#include "../toxcore/crypto_core.h"
 #include "../toxcore/net_crypto.h"
 
 static void rand_bytes(uint8_t *b, size_t blen)
@@ -19,7 +20,7 @@ static void rand_bytes(uint8_t *b, size_t blen)
     size_t i;
 
     for (i = 0; i < blen; i++) {
-        b[i] = rand();
+        b[i] = random_u08();
     }
 }
 
@@ -166,7 +167,7 @@ START_TEST(test_endtoend)
     // Test 100 random messages and keypairs
     for (testno = 0; testno < 100; testno++) {
         //Generate random message (random length from 100 to 500)
-        mlen = (rand() % 400) + 100;
+        mlen = (random_u32() % 400) + 100;
         rand_bytes(m, mlen);
         rand_bytes(n, CRYPTO_NONCE_SIZE);
 
@@ -303,7 +304,7 @@ START_TEST(test_increment_nonce)
     uint8_t n[CRYPTO_NONCE_SIZE];
 
     for (i = 0; i < CRYPTO_NONCE_SIZE; ++i) {
-        n[i] = rand();
+        n[i] = random_u08();
     }
 
     uint8_t n1[CRYPTO_NONCE_SIZE];
@@ -317,7 +318,7 @@ START_TEST(test_increment_nonce)
     }
 
     for (i = 0; i < (1 << 18); ++i) {
-        uint32_t r = rand();
+        const uint32_t r = random_u32();
         increment_nonce_number_cmp(n, r);
         increment_nonce_number(n1, r);
         ck_assert_msg(memcmp(n, n1, CRYPTO_NONCE_SIZE) == 0, "Bad increment_nonce_number function");
diff --git a/auto_tests/dht_test.c b/auto_tests/dht_test.c
index 034147b980..803dad7625 100644
--- a/auto_tests/dht_test.c
+++ b/auto_tests/dht_test.c
@@ -13,6 +13,7 @@
 
 #include "helpers.h"
 
+#include "../toxcore/crypto_core.h"
 #ifndef DHT_C_INCLUDED
 #include "../toxcore/DHT.c"
 #endif // DHT_C_INCLUDED
@@ -115,7 +116,7 @@ static void test_addto_lists_update(DHT            *dht,
     uint8_t ipv6 = ip_port->ip.family == TOX_AF_INET6 ? 1 : 0;
 
     // check id update for existing ip_port
-    test = rand() % length;
+    test = random_u32() % length;
     ipport_copy(&test_ipp, ipv6 ? &list[test].assoc6.ip_port : &list[test].assoc4.ip_port);
 
     random_bytes(test_id, sizeof(test_id));
@@ -128,8 +129,8 @@ static void test_addto_lists_update(DHT            *dht,
                   "Client IP_Port is incorrect");
 
     // check ip_port update for existing id
-    test = rand() % length;
-    test_ipp.port = rand() % TOX_PORT_DEFAULT;
+    test = random_u32() % length;
+    test_ipp.port = random_u32() % TOX_PORT_DEFAULT;
     id_copy(test_id, list[test].public_key);
 
     used = addto_lists(dht, test_ipp, test_id);
@@ -140,8 +141,8 @@ static void test_addto_lists_update(DHT            *dht,
                   "Client IP_Port is incorrect");
 
     // check ip_port update for existing id and ip_port (... port ... id ...)
-    test1 = rand() % (length / 2);
-    test2 = rand() % (length / 2) + length / 2;
+    test1 = random_u32() % (length / 2);
+    test2 = random_u32() % (length / 2) + length / 2;
 
     ipport_copy(&test_ipp, ipv6 ? &list[test1].assoc6.ip_port : &list[test1].assoc4.ip_port);
     id_copy(test_id, list[test2].public_key);
@@ -159,8 +160,8 @@ static void test_addto_lists_update(DHT            *dht,
                   "Client IP_Port is incorrect");
 
     // check ip_port update for existing id and ip_port (... id ... port ...)
-    test1 = rand() % (length / 2);
-    test2 = rand() % (length / 2) + length / 2;
+    test1 = random_u32() % (length / 2);
+    test2 = random_u32() % (length / 2) + length / 2;
 
     ipport_copy(&test_ipp, ipv6 ? &list[test2].assoc6.ip_port : &list[test2].assoc4.ip_port);
     id_copy(test_id, list[test1].public_key);
@@ -192,9 +193,9 @@ static void test_addto_lists_bad(DHT            *dht,
     random_bytes(public_key, sizeof(public_key));
     mark_all_good(list, length, ipv6);
 
-    test1 = rand() % (length / 3);
-    test2 = rand() % (length / 3) + length / 3;
-    test3 = rand() % (length / 3) + 2 * length / 3;
+    test1 = random_u32() % (length / 3);
+    test2 = random_u32() % (length / 3) + length / 3;
+    test3 = random_u32() % (length / 3) + 2 * length / 3;
     ck_assert_msg(!(test1 == test2 || test1 == test3 || test2 == test3), "Wrong test indices are chosen");
 
     id_copy((uint8_t *)&test_id1, list[test1].public_key);
@@ -236,9 +237,9 @@ static void test_addto_lists_possible_bad(DHT            *dht,
     random_bytes(public_key, sizeof(public_key));
     mark_all_good(list, length, ipv6);
 
-    test1 = rand() % (length / 3);
-    test2 = rand() % (length / 3) + length / 3;
-    test3 = rand() % (length / 3) + 2 * length / 3;
+    test1 = random_u32() % (length / 3);
+    test2 = random_u32() % (length / 3) + length / 3;
+    test3 = random_u32() % (length / 3) + 2 * length / 3;
     ck_assert_msg(!(test1 == test2 || test1 == test3 || test2 == test3), "Wrong test indices are chosen");
 
     id_copy((uint8_t *)&test_id1, list[test1].public_key);
@@ -491,8 +492,8 @@ static void test_list_main(void)
 
             IP_Port ip_port;
             ip_init(&ip_port.ip, 0);
-            ip_port.ip.ip.v4.uint32 = rand();
-            ip_port.port = rand() % (UINT16_MAX - 1);
+            ip_port.ip.ip.v4.uint32 = random_u32();
+            ip_port.port = random_u32() % (UINT16_MAX - 1);
             ++ip_port.port;
             addto_lists(dhts[j], ip_port, dhts[i]->self_public_key);
         }
@@ -626,8 +627,8 @@ START_TEST(test_DHT_test)
 
     for (i = 0; i < NUM_DHT_FRIENDS; ++i) {
 loop_top:
-        pairs[i].tox1 = rand() % NUM_DHT;
-        pairs[i].tox2 = (pairs[i].tox1 + (rand() % (NUM_DHT - 1)) + 1) % NUM_DHT;
+        pairs[i].tox1 = random_u32() % NUM_DHT;
+        pairs[i].tox2 = (pairs[i].tox1 + (random_u32() % (NUM_DHT - 1)) + 1) % NUM_DHT;
 
         for (j = 0; j < i; ++j) {
             if (pairs[j].tox2 == pairs[i].tox2 && pairs[j].tox1 == pairs[i].tox1) {
diff --git a/auto_tests/save_friend_test.c b/auto_tests/save_friend_test.c
index a7b41f5261..1e90e692c4 100644
--- a/auto_tests/save_friend_test.c
+++ b/auto_tests/save_friend_test.c
@@ -7,6 +7,7 @@
 
 #include "helpers.h"
 #include "../toxcore/ccompat.h"
+#include "../toxcore/crypto_core.h"
 #include "../toxcore/tox.h"
 
 #include <assert.h>
@@ -27,7 +28,7 @@ static void set_random(Tox *m, bool (*setter)(Tox *, const uint8_t *, size_t, TO
     uint32_t i;
 
     for (i = 0; i < length; ++i) {
-        text[i] = rand();
+        text[i] = random_u08();
     }
 
     setter(m, text, SIZEOF_VLA(text), nullptr);
diff --git a/auto_tests/tox_many_tcp_test.c b/auto_tests/tox_many_tcp_test.c
index 6c3f235051..34b01d1602 100644
--- a/auto_tests/tox_many_tcp_test.c
+++ b/auto_tests/tox_many_tcp_test.c
@@ -15,6 +15,7 @@
 #include <stdlib.h>
 #include <time.h>
 
+#include "../toxcore/crypto_core.h"
 #include "../toxcore/tox.h"
 #include "../toxcore/util.h"
 
@@ -84,8 +85,8 @@ START_TEST(test_many_clients_tcp)
 
     for (i = 0; i < NUM_FRIENDS; ++i) {
 loop_top:
-        pairs[i].tox1 = rand() % NUM_TOXES_TCP;
-        pairs[i].tox2 = (pairs[i].tox1 + rand() % (NUM_TOXES_TCP - 1) + 1) % NUM_TOXES_TCP;
+        pairs[i].tox1 = random_u32() % NUM_TOXES_TCP;
+        pairs[i].tox2 = (pairs[i].tox1 + random_u32() % (NUM_TOXES_TCP - 1) + 1) % NUM_TOXES_TCP;
 
         for (j = 0; j < i; ++j) {
             if (pairs[j].tox2 == pairs[i].tox1 && pairs[j].tox1 == pairs[i].tox2) {
@@ -178,8 +179,8 @@ START_TEST(test_many_clients_tcp_b)
 
     for (i = 0; i < NUM_FRIENDS; ++i) {
 loop_top:
-        pairs[i].tox1 = rand() % NUM_TOXES_TCP;
-        pairs[i].tox2 = (pairs[i].tox1 + rand() % (NUM_TOXES_TCP - 1) + 1) % NUM_TOXES_TCP;
+        pairs[i].tox1 = random_u32() % NUM_TOXES_TCP;
+        pairs[i].tox2 = (pairs[i].tox1 + random_u32() % (NUM_TOXES_TCP - 1) + 1) % NUM_TOXES_TCP;
 
         for (j = 0; j < i; ++j) {
             if (pairs[j].tox2 == pairs[i].tox1 && pairs[j].tox1 == pairs[i].tox2) {
diff --git a/auto_tests/tox_many_test.c b/auto_tests/tox_many_test.c
index 29f3af68e9..4318b29b4f 100644
--- a/auto_tests/tox_many_test.c
+++ b/auto_tests/tox_many_test.c
@@ -15,6 +15,7 @@
 #include <stdlib.h>
 #include <time.h>
 
+#include "../toxcore/crypto_core.h"
 #include "../toxcore/tox.h"
 #include "../toxcore/util.h"
 
@@ -61,8 +62,8 @@ static void test_many_clients(void)
 
     for (uint32_t i = 0; i < NUM_FRIENDS; ++i) {
 loop_top:
-        pairs[i].tox1 = rand() % NUM_TOXES;
-        pairs[i].tox2 = (pairs[i].tox1 + rand() % (NUM_TOXES - 1) + 1) % NUM_TOXES;
+        pairs[i].tox1 = random_u32() % NUM_TOXES;
+        pairs[i].tox2 = (pairs[i].tox1 + random_u32() % (NUM_TOXES - 1) + 1) % NUM_TOXES;
 
         for (uint32_t j = 0; j < i; ++j) {
             if (pairs[j].tox2 == pairs[i].tox1 && pairs[j].tox1 == pairs[i].tox2) {
diff --git a/auto_tests/tox_one_test.c b/auto_tests/tox_one_test.c
index f3323bc92b..48e2f7918f 100644
--- a/auto_tests/tox_one_test.c
+++ b/auto_tests/tox_one_test.c
@@ -11,6 +11,7 @@
 #include <time.h>
 
 #include "../toxcore/ccompat.h"
+#include "../toxcore/crypto_core.h"
 #include "../toxcore/tox.h"
 #include "../toxcore/util.h"
 
@@ -21,11 +22,11 @@ static void set_random_name_and_status_message(Tox *tox, uint8_t *name, uint8_t
     int i;
 
     for (i = 0; i < TOX_MAX_NAME_LENGTH; ++i) {
-        name[i] = rand();
+        name[i] = random_u08();
     }
 
     for (i = 0; i < TOX_MAX_STATUS_MESSAGE_LENGTH; ++i) {
-        status_message[i] = rand();
+        status_message[i] = random_u08();
     }
 }
 
diff --git a/toxcore/crypto_core.api.h b/toxcore/crypto_core.api.h
index bb2c0a13b8..e9e8aeb273 100644
--- a/toxcore/crypto_core.api.h
+++ b/toxcore/crypto_core.api.h
@@ -116,6 +116,11 @@ static int32_t public_key_cmp(
 
 namespace random {
 
+/**
+ * Return a random 8 bit integer.
+ */
+static uint8_t u08();
+
 /**
  * Return a random 16 bit integer.
  */
diff --git a/toxcore/crypto_core.c b/toxcore/crypto_core.c
index 26589219ed..b2f0e5f0d3 100644
--- a/toxcore/crypto_core.c
+++ b/toxcore/crypto_core.c
@@ -86,6 +86,13 @@ int32_t public_key_cmp(const uint8_t *pk1, const uint8_t *pk2)
     return crypto_verify_32(pk1, pk2);
 }
 
+uint8_t random_u08(void)
+{
+    uint8_t randnum;
+    randombytes(&randnum, 1);
+    return randnum;
+}
+
 uint16_t random_u16(void)
 {
     uint16_t randnum;
diff --git a/toxcore/crypto_core.h b/toxcore/crypto_core.h
index 2c83fd255a..e7e913b681 100644
--- a/toxcore/crypto_core.h
+++ b/toxcore/crypto_core.h
@@ -126,6 +126,11 @@ void crypto_sha512(uint8_t *hash, const uint8_t *data, size_t length);
  */
 int32_t public_key_cmp(const uint8_t *pk1, const uint8_t *pk2);
 
+/**
+ * Return a random 8 bit integer.
+ */
+uint8_t random_u08(void);
+
 /**
  * Return a random 16 bit integer.
  */