diff --git a/clientconnudpl.go b/clientconnudpl.go
index b6dbcb38..4c3210ce 100644
--- a/clientconnudpl.go
+++ b/clientconnudpl.go
@@ -1,7 +1,7 @@
 package gortsplib
 
 import (
-	"math/rand"
+	"crypto/rand"
 	"net"
 	"strconv"
 	"sync"
@@ -18,6 +18,16 @@ const (
 	clientConnUDPKernelReadBufferSize = 0x80000
 )
 
+func randUint32() uint32 {
+	var b [4]byte
+	rand.Read(b[:])
+	return uint32(b[0]<<24) | uint32(b[1]<<16) | uint32(b[2]<<8) | uint32(b[3])
+}
+
+func randIntn(n int) int {
+	return int(randUint32() & (uint32(n) - 1))
+}
+
 type clientConnUDPListener struct {
 	cc            *ClientConn
 	pc            *net.UDPConn
@@ -40,7 +50,7 @@ func newClientConnUDPListenerPair(cc *ClientConn) (*clientConnUDPListener, *clie
 	// choose two consecutive ports in range 65535-10000
 	// rtp must be even and rtcp odd
 	for {
-		rtpPort := (rand.Intn((65535-10000)/2) * 2) + 10000
+		rtpPort := (randIntn((65535-10000)/2) * 2) + 10000
 		rtpListener, err := newClientConnUDPListener(cc, false, ":"+strconv.FormatInt(int64(rtpPort), 10))
 		if err != nil {
 			continue
diff --git a/pkg/rtcpreceiver/rtcpreceiver.go b/pkg/rtcpreceiver/rtcpreceiver.go
index e49ba690..2f5af518 100644
--- a/pkg/rtcpreceiver/rtcpreceiver.go
+++ b/pkg/rtcpreceiver/rtcpreceiver.go
@@ -2,7 +2,7 @@
 package rtcpreceiver
 
 import (
-	"math/rand"
+	"crypto/rand"
 	"sync"
 	"time"
 
@@ -11,6 +11,12 @@ import (
 	"github.com/aler9/gortsplib/pkg/base"
 )
 
+func randUint32() uint32 {
+	var b [4]byte
+	rand.Read(b[:])
+	return uint32(b[0]<<24) | uint32(b[1]<<16) | uint32(b[2]<<8) | uint32(b[3])
+}
+
 // RTCPReceiver is a utility to generate RTCP receiver reports.
 type RTCPReceiver struct {
 	receiverSSRC uint32
@@ -39,7 +45,7 @@ func New(receiverSSRC *uint32, clockRate int) *RTCPReceiver {
 	return &RTCPReceiver{
 		receiverSSRC: func() uint32 {
 			if receiverSSRC == nil {
-				return rand.Uint32()
+				return randUint32()
 			}
 			return *receiverSSRC
 		}(),
diff --git a/pkg/rtpaac/encoder.go b/pkg/rtpaac/encoder.go
index 0bd4ce76..6cd5d1f2 100644
--- a/pkg/rtpaac/encoder.go
+++ b/pkg/rtpaac/encoder.go
@@ -1,8 +1,8 @@
 package rtpaac
 
 import (
+	"crypto/rand"
 	"encoding/binary"
-	"math/rand"
 	"time"
 
 	"github.com/pion/rtp"
@@ -13,6 +13,12 @@ const (
 	rtpPayloadMaxSize = 1460 // 1500 (mtu) - 20 (ip header) - 8 (udp header) - 12 (rtp header)
 )
 
+func randUint32() uint32 {
+	var b [4]byte
+	rand.Read(b[:])
+	return uint32(b[0]<<24) | uint32(b[1]<<16) | uint32(b[2]<<8) | uint32(b[3])
+}
+
 // Encoder is a RTP/AAC encoder.
 type Encoder struct {
 	payloadType    uint8
@@ -35,19 +41,19 @@ func NewEncoder(payloadType uint8,
 			if sequenceNumber != nil {
 				return *sequenceNumber
 			}
-			return uint16(rand.Uint32())
+			return uint16(randUint32())
 		}(),
 		ssrc: func() uint32 {
 			if ssrc != nil {
 				return *ssrc
 			}
-			return rand.Uint32()
+			return randUint32()
 		}(),
 		initialTs: func() uint32 {
 			if initialTs != nil {
 				return *initialTs
 			}
-			return rand.Uint32()
+			return randUint32()
 		}(),
 	}
 }
diff --git a/pkg/rtph264/encoder.go b/pkg/rtph264/encoder.go
index 7273d62f..47119b7a 100644
--- a/pkg/rtph264/encoder.go
+++ b/pkg/rtph264/encoder.go
@@ -1,8 +1,8 @@
 package rtph264
 
 import (
+	"crypto/rand"
 	"encoding/binary"
-	"math/rand"
 	"time"
 
 	"github.com/pion/rtp"
@@ -14,6 +14,12 @@ const (
 	rtpClockRate      = 90000 // h264 always uses 90khz
 )
 
+func randUint32() uint32 {
+	var b [4]byte
+	rand.Read(b[:])
+	return uint32(b[0]<<24) | uint32(b[1]<<16) | uint32(b[2]<<8) | uint32(b[3])
+}
+
 // Encoder is a RTP/H264 encoder.
 type Encoder struct {
 	payloadType    uint8
@@ -33,19 +39,19 @@ func NewEncoder(payloadType uint8,
 			if sequenceNumber != nil {
 				return *sequenceNumber
 			}
-			return uint16(rand.Uint32())
+			return uint16(randUint32())
 		}(),
 		ssrc: func() uint32 {
 			if ssrc != nil {
 				return *ssrc
 			}
-			return rand.Uint32()
+			return randUint32()
 		}(),
 		initialTs: func() uint32 {
 			if initialTs != nil {
 				return *initialTs
 			}
-			return rand.Uint32()
+			return randUint32()
 		}(),
 	}
 }
diff --git a/server.go b/server.go
index 20d0d523..53f34c38 100644
--- a/server.go
+++ b/server.go
@@ -32,7 +32,7 @@ func extractPort(address string) (int, error) {
 func newSessionSecretID(sessions map[string]*ServerSession) (string, error) {
 	for {
 		b := make([]byte, 4)
-		_, err := rand.Read(b)
+		_, err := rand.Read(b[:])
 		if err != nil {
 			return "", err
 		}