diff --git a/src/core/tcp.go b/src/core/tcp.go
index 5c3e506b..4dc36a08 100644
--- a/src/core/tcp.go
+++ b/src/core/tcp.go
@@ -54,7 +54,7 @@ type TcpListener struct {
 }
 
 type TcpUpgrade struct {
-	upgrade func(c net.Conn) (net.Conn, error)
+	upgrade func(c net.Conn, o *tcpOptions) (net.Conn, error)
 	name    string
 }
 
@@ -361,7 +361,7 @@ func (t *tcp) handler(sock net.Conn, incoming bool, options tcpOptions) chan str
 	var upgraded bool
 	if options.upgrade != nil {
 		var err error
-		if sock, err = options.upgrade.upgrade(sock); err != nil {
+		if sock, err = options.upgrade.upgrade(sock, &options); err != nil {
 			t.links.core.log.Errorln("TCP handler upgrade failed:", err)
 			return nil
 		}
diff --git a/src/core/tls.go b/src/core/tls.go
index 4fdcf997..4c25225b 100644
--- a/src/core/tls.go
+++ b/src/core/tls.go
@@ -9,6 +9,7 @@ import (
 	"crypto/x509/pkix"
 	"encoding/hex"
 	"encoding/pem"
+	"errors"
 	"log"
 	"math/big"
 	"net"
@@ -76,16 +77,47 @@ func (t *tcptls) init(tcp *tcp) {
 	}
 }
 
-func (t *tcptls) upgradeListener(c net.Conn) (net.Conn, error) {
-	conn := tls.Server(c, t.config)
+func (t *tcptls) configForOptions(options *tcpOptions) *tls.Config {
+	config := *t.config
+	config.VerifyPeerCertificate = func(rawCerts [][]byte, _ [][]*x509.Certificate) error {
+		if len(rawCerts) != 1 {
+			return errors.New("tls not exactly 1 cert")
+		}
+		cert, err := x509.ParseCertificate(rawCerts[0])
+		if err != nil {
+			return errors.New("tls failed to parse cert")
+		}
+		if cert.PublicKeyAlgorithm != x509.Ed25519 {
+			return errors.New("tls wrong cert algorithm")
+		}
+		pk := cert.PublicKey.(ed25519.PublicKey)
+		var key keyArray
+		copy(key[:], pk)
+		// If options does not have a pinned key, then pin one now
+		if options.pinnedEd25519Keys == nil {
+			options.pinnedEd25519Keys = make(map[keyArray]struct{})
+			options.pinnedEd25519Keys[key] = struct{}{}
+		}
+		if _, isIn := options.pinnedEd25519Keys[key]; !isIn {
+			return errors.New("tls key does not match pinned key")
+		}
+		return nil
+	}
+	return &config
+}
+
+func (t *tcptls) upgradeListener(c net.Conn, options *tcpOptions) (net.Conn, error) {
+	config := t.configForOptions(options)
+	conn := tls.Server(c, config)
 	if err := conn.Handshake(); err != nil {
 		return c, err
 	}
 	return conn, nil
 }
 
-func (t *tcptls) upgradeDialer(c net.Conn) (net.Conn, error) {
-	conn := tls.Client(c, t.config)
+func (t *tcptls) upgradeDialer(c net.Conn, options *tcpOptions) (net.Conn, error) {
+	config := t.configForOptions(options)
+	conn := tls.Client(c, config)
 	if err := conn.Handshake(); err != nil {
 		return c, err
 	}