diff --git a/cli/ss-server/main.go b/cli/ss-server/main.go
index 0b34254..058a824 100644
--- a/cli/ss-server/main.go
+++ b/cli/ss-server/main.go
@@ -184,7 +184,7 @@ func newServer(f *flags) (*server, error) {
 			}
 			key = kb
 		}
-		service, err := shadowaead.NewService(f.Method, key, []byte(f.Password), random.Blake3KeyedHash(), false, udpTimeout, s)
+		service, err := shadowaead.NewService(f.Method, key, []byte(f.Password), random.Default, false, udpTimeout, s)
 		if err != nil {
 			return nil, err
 		}
@@ -201,7 +201,7 @@ func newServer(f *flags) (*server, error) {
 			}
 			copy(key[:], kb)
 		}
-		service, err := shadowaead_2022.NewService(f.Method, key, random.Blake3KeyedHash(), udpTimeout, s)
+		service, err := shadowaead_2022.NewService(f.Method, key, random.Default, udpTimeout, s)
 		if err != nil {
 			return nil, err
 		}
diff --git a/common/random/rng.go b/common/random/rng.go
index 24374d7..62a897e 100644
--- a/common/random/rng.go
+++ b/common/random/rng.go
@@ -4,18 +4,32 @@ import (
 	"crypto/rand"
 	"encoding/binary"
 	"io"
+	"sync"
 
 	"github.com/sagernet/sing/common"
 	"lukechampine.com/blake3"
 )
 
-var System = rand.Reader
+var System = &Source{rand.Reader}
 
-func Blake3KeyedHash() Source {
+var Default = Blake3KeyedHash()
+
+func Blake3KeyedHash() *Source {
 	key := make([]byte, 32)
 	common.Must1(io.ReadFull(System, key))
 	h := blake3.New(1024, key)
-	return Source{h.XOF()}
+	return &Source{&SyncReader{Reader: h.XOF()}}
+}
+
+type SyncReader struct {
+	io.Reader
+	sync.Mutex
+}
+
+func (r *SyncReader) Read(p []byte) (n int, err error) {
+	r.Lock()
+	defer r.Unlock()
+	return r.Reader.Read(p)
 }
 
 const (
diff --git a/protocol/shadowsocks/service.go b/protocol/shadowsocks/service.go
index 37faebf..7c0fc5e 100644
--- a/protocol/shadowsocks/service.go
+++ b/protocol/shadowsocks/service.go
@@ -2,6 +2,8 @@ package shadowsocks
 
 import (
 	"context"
+	"fmt"
+	"net"
 
 	E "github.com/sagernet/sing/common/exceptions"
 	M "github.com/sagernet/sing/common/metadata"
@@ -29,3 +31,31 @@ type UserContext[U comparable] struct {
 	context.Context
 	User U
 }
+
+type ServerConnError struct {
+	net.Conn
+	Source *M.AddrPort
+	Cause  error
+}
+
+func (e *ServerConnError) Unwrap() error {
+	return e.Cause
+}
+
+func (e *ServerConnError) Error() string {
+	return fmt.Sprint("shadowsocks: serve TCP from ", e.Source, ": ", e.Cause)
+}
+
+type ServerPacketError struct {
+	socks.PacketConn
+	Source *M.AddrPort
+	Cause  error
+}
+
+func (e *ServerPacketError) Unwrap() error {
+	return e.Cause
+}
+
+func (e *ServerPacketError) Error() string {
+	return fmt.Sprint("shadowsocks: serve UDP from ", e.Source, ": ", e.Cause)
+}
diff --git a/protocol/shadowsocks/shadowaead/service.go b/protocol/shadowsocks/shadowaead/service.go
index 9ac1b7e..0d929d7 100644
--- a/protocol/shadowsocks/shadowaead/service.go
+++ b/protocol/shadowsocks/shadowaead/service.go
@@ -79,6 +79,14 @@ func NewService(method string, key []byte, password []byte, secureRNG io.Reader,
 }
 
 func (s *Service) NewConnection(ctx context.Context, conn net.Conn, metadata M.Metadata) error {
+	err := s.newConnection(ctx, conn, metadata)
+	if err != nil {
+		err = &shadowsocks.ServerConnError{Conn: conn, Source: metadata.Source, Cause: err}
+	}
+	return err
+}
+
+func (s *Service) newConnection(ctx context.Context, conn net.Conn, metadata M.Metadata) error {
 	_salt := buf.Make(s.keySaltLength)
 	salt := common.Dup(_salt)
 
@@ -191,6 +199,14 @@ func (c *serverConn) WriterReplaceable() bool {
 }
 
 func (s *Service) NewPacket(conn socks.PacketConn, buffer *buf.Buffer, metadata M.Metadata) error {
+	err := s.newPacket(conn, buffer, metadata)
+	if err != nil {
+		err = &shadowsocks.ServerPacketError{PacketConn: conn, Source: metadata.Source, Cause: err}
+	}
+	return err
+}
+
+func (s *Service) newPacket(conn socks.PacketConn, buffer *buf.Buffer, metadata M.Metadata) error {
 	if buffer.Len() < s.keySaltLength {
 		return E.New("bad packet")
 	}
diff --git a/protocol/shadowsocks/shadowaead_2022/service.go b/protocol/shadowsocks/shadowaead_2022/service.go
index 2e7dac3..505bdb6 100644
--- a/protocol/shadowsocks/shadowaead_2022/service.go
+++ b/protocol/shadowsocks/shadowaead_2022/service.go
@@ -73,6 +73,14 @@ func NewService(method string, psk [KeySaltSize]byte, secureRNG io.Reader, udpTi
 }
 
 func (s *Service) NewConnection(ctx context.Context, conn net.Conn, metadata M.Metadata) error {
+	err := s.newConnection(ctx, conn, metadata)
+	if err != nil {
+		err = &shadowsocks.ServerConnError{Conn: conn, Source: metadata.Source, Cause: err}
+	}
+	return err
+}
+
+func (s *Service) newConnection(ctx context.Context, conn net.Conn, metadata M.Metadata) error {
 	requestSalt := make([]byte, KeySaltSize)
 	_, err := io.ReadFull(conn, requestSalt)
 	if err != nil {
@@ -230,6 +238,14 @@ func (c *serverConn) WriterReplaceable() bool {
 }
 
 func (s *Service) NewPacket(conn socks.PacketConn, buffer *buf.Buffer, metadata M.Metadata) error {
+	err := s.newPacket(conn, buffer, metadata)
+	if err != nil {
+		err = &shadowsocks.ServerPacketError{PacketConn: conn, Source: metadata.Source, Cause: err}
+	}
+	return err
+}
+
+func (s *Service) newPacket(conn socks.PacketConn, buffer *buf.Buffer, metadata M.Metadata) error {
 	var packetHeader []byte
 	if s.udpCipher != nil {
 		_, err := s.udpCipher.Open(buffer.Index(PacketNonceSize), buffer.To(PacketNonceSize), buffer.From(PacketNonceSize), nil)
diff --git a/protocol/shadowsocks/shadowaead_2022/service_multi.go b/protocol/shadowsocks/shadowaead_2022/service_multi.go
index 5da4aef..561448f 100644
--- a/protocol/shadowsocks/shadowaead_2022/service_multi.go
+++ b/protocol/shadowsocks/shadowaead_2022/service_multi.go
@@ -73,6 +73,14 @@ func NewMultiService[U comparable](method string, iPSK [KeySaltSize]byte, secure
 }
 
 func (s *MultiService[U]) NewConnection(ctx context.Context, conn net.Conn, metadata M.Metadata) error {
+	err := s.newConnection(ctx, conn, metadata)
+	if err != nil {
+		err = &shadowsocks.ServerConnError{Conn: conn, Source: metadata.Source, Cause: err}
+	}
+	return err
+}
+
+func (s *MultiService[U]) newConnection(ctx context.Context, conn net.Conn, metadata M.Metadata) error {
 	requestSalt := make([]byte, KeySaltSize)
 	_, err := io.ReadFull(conn, requestSalt)
 	if err != nil {
@@ -166,6 +174,14 @@ func (s *MultiService[U]) NewConnection(ctx context.Context, conn net.Conn, meta
 }
 
 func (s *MultiService[U]) NewPacket(conn socks.PacketConn, buffer *buf.Buffer, metadata M.Metadata) error {
+	err := s.newPacket(conn, buffer, metadata)
+	if err != nil {
+		err = &shadowsocks.ServerPacketError{PacketConn: conn, Source: metadata.Source, Cause: err}
+	}
+	return err
+}
+
+func (s *MultiService[U]) newPacket(conn socks.PacketConn, buffer *buf.Buffer, metadata M.Metadata) error {
 	packetHeader := buffer.To(aes.BlockSize)
 	s.udpBlockCipher.Decrypt(packetHeader, packetHeader)
 
diff --git a/protocol/socks/packet_conn.go b/protocol/socks/packet_conn.go
index 7438a12..125c6e0 100644
--- a/protocol/socks/packet_conn.go
+++ b/protocol/socks/packet_conn.go
@@ -27,6 +27,7 @@ type PacketConn interface {
 
 	Close() error
 	LocalAddr() net.Addr
+	RemoteAddr() net.Addr
 	SetDeadline(t time.Time) error
 	SetReadDeadline(t time.Time) error
 	SetWriteDeadline(t time.Time) error
@@ -42,6 +43,10 @@ type UDPConnectionHandler interface {
 
 type PacketConnStub struct{}
 
+func (s *PacketConnStub) RemoteAddr() net.Addr {
+	return &common.DummyAddr{}
+}
+
 func (s *PacketConnStub) SetDeadline(t time.Time) error {
 	return os.ErrInvalid
 }
@@ -113,3 +118,7 @@ func (p *PacketConnWrapper) ReadPacket(buffer *buf.Buffer) (*M.AddrPort, error)
 func (p *PacketConnWrapper) WritePacket(buffer *buf.Buffer, destination *M.AddrPort) error {
 	return common.Error(p.WriteTo(buffer.Bytes(), destination.UDPAddr()))
 }
+
+func (p *PacketConnWrapper) RemoteAddr() net.Addr {
+	return &common.DummyAddr{}
+}
diff --git a/transport/tls/cert.go b/transport/tls/cert.go
index 0f08ba6..468dcb1 100644
--- a/transport/tls/cert.go
+++ b/transport/tls/cert.go
@@ -16,7 +16,7 @@ import (
 )
 
 func GenerateCertificate(hosts ...string) (*tls.Certificate, error) {
-	rng := random.Blake3KeyedHash()
+	rng := random.System
 	r := rand.New(rng)
 
 	privateKey, err := rsa.GenerateKey(rng, 2048)