diff --git a/13.go b/13.go
index 4d72c93..da02bfb 100644
--- a/13.go
+++ b/13.go
@@ -22,6 +22,7 @@ import (
 	"time"
 
 	sidh "github_com/cloudflare/sidh/sidh"
+	sike "github_com/cloudflare/sidh/sike"
 	"golang_org/x/crypto/curve25519"
 )
 
@@ -32,14 +33,22 @@ const numSessionTickets = 2
 type secretLabel int
 
 const (
-	x25519SharedSecretSz = 32
-
-	P503PubKeySz                  = 378
-	P503PrvKeySz                  = 32
-	P503SharedSecretSz            = 126
-	SIDHp503Curve25519PubKeySz    = x25519SharedSecretSz + P503PubKeySz
-	SIDHp503Curve25519PrvKeySz    = x25519SharedSecretSz + P503PrvKeySz
-	SIDHp503Curve25519SharedKeySz = x25519SharedSecretSz + P503SharedSecretSz
+	// Both public key and shared secret size
+	x25519Sz = 32
+
+	SIDHp503PubKeySz              = 378
+	SIDHp503PrvKeySz              = 32
+	SIDHp503SharedSecretSz        = 126
+	SIDHp503Curve25519PubKeySz    = x25519Sz + SIDHp503PubKeySz
+	SIDHp503Curve25519PrvKeySz    = x25519Sz + SIDHp503PrvKeySz
+	SIDHp503Curve25519SharedKeySz = x25519Sz + SIDHp503SharedSecretSz
+
+	SIKEp503SharedSecretSz        = 16
+	SIKEp503CtSz                  = SIDHp503PubKeySz + 24
+	SIKEp503Curve25519CtSz        = x25519Sz + SIKEp503CtSz
+	SIKEp503Curve25519PubKeySz    = x25519Sz + SIDHp503PubKeySz
+	SIKEp503Curve25519PrvKeySz    = x25519Sz + SIDHp503PrvKeySz + 24
+	SIKEp503Curve25519SharedKeySz = x25519Sz + SIKEp503SharedSecretSz
 )
 
 const (
@@ -111,12 +120,18 @@ func (defaultServerKEX) keyAgreementServer(c *Conn, clientKS keyShare) ([]byte,
 type kexNIST struct{ defaultServerKEX }     // Used by NIST curves; P-256, P-384, P-512
 type kexX25519 struct{ defaultServerKEX }   // Used by X25519
 type kexSIDHp503 struct{ defaultServerKEX } // Used by SIDH/P503
+type kexSIKEp503 struct{}                   // Used by SIKE/P503
 type kexHybridSIDHp503X25519 struct {
 	defaultServerKEX
 	classicKEX kexX25519
 	pqKEX      kexSIDHp503
 } // Used by SIDH-ECDH hybrid scheme
 
+type kexHybridSIKEp503X25519 struct {
+	classicKEX kexX25519
+	pqKEX      kexSIKEp503
+} // Used by SIKE-ECDHE hybrid scheme
+
 // Routing map for key exchange strategies
 var kexStrat = map[CurveID]kex{
 	CurveP256:                &kexNIST{},
@@ -124,6 +139,7 @@ var kexStrat = map[CurveID]kex{
 	CurveP521:                &kexNIST{},
 	X25519:                   &kexX25519{},
 	HybridSIDHp503Curve25519: &kexHybridSIDHp503X25519{},
+	HybridSIKEp503Curve25519: &kexHybridSIKEp503X25519{},
 }
 
 func newKeySchedule13(suite *cipherSuite, config *Config, clientRandom []byte) *keySchedule13 {
@@ -1238,7 +1254,7 @@ func (kexNIST) keyAgreementClient(c *Conn, ks keyShare, secretKey []byte) ([]byt
 
 // KEX: X25519
 func (kexX25519) generate(c *Conn, groupId CurveID) ([]byte, keyShare, error) {
-	var scalar, public [x25519SharedSecretSz]byte
+	var scalar, public [x25519Sz]byte
 	if _, err := io.ReadFull(c.config.rand(), scalar[:]); err != nil {
 		return nil, keyShare{}, err
 	}
@@ -1247,8 +1263,8 @@ func (kexX25519) generate(c *Conn, groupId CurveID) ([]byte, keyShare, error) {
 }
 
 func (kexX25519) keyAgreementClient(c *Conn, ks keyShare, secretKey []byte) ([]byte, error) {
-	var theirPublic, sharedKey, scalar [x25519SharedSecretSz]byte
-	if len(ks.data) != x25519SharedSecretSz {
+	var theirPublic, sharedKey, scalar [x25519Sz]byte
+	if len(ks.data) != x25519Sz {
 		return nil, errors.New("tls: wrong shared secret size")
 	}
 	copy(theirPublic[:], ks.data)
@@ -1270,9 +1286,8 @@ func (kexSIDHp503) generate(c *Conn, groupId CurveID) ([]byte, keyShare, error)
 
 func (kexSIDHp503) keyAgreementClient(c *Conn, ks keyShare, key []byte) ([]byte, error) {
 	var prvVariant, pubVariant = getSidhKeyVariant(c.isClient)
-	var prvKeySize = P503PrvKeySz
 
-	if len(ks.data) != P503PubKeySz || len(key) != prvKeySize {
+	if len(ks.data) != SIDHp503PubKeySz || len(key) != SIDHp503PrvKeySz {
 		return nil, errors.New("tls: wrong key size")
 	}
 
@@ -1309,20 +1324,20 @@ func (kex *kexHybridSIDHp503X25519) generate(c *Conn, groupId CurveID) (private
 	if err != nil {
 		return
 	}
-	copy(prvHybrid[x25519SharedSecretSz:], private)
-	copy(pubHybrid[x25519SharedSecretSz:], ks.data)
+	copy(prvHybrid[x25519Sz:], private)
+	copy(pubHybrid[x25519Sz:], ks.data)
 	return prvHybrid[:], keyShare{group: HybridSIDHp503Curve25519, data: pubHybrid[:]}, nil
 }
 
-func (kex *kexHybridSIDHp503X25519) keyAgreementClient(c *Conn, ks keyShare, key []byte) ([]byte, error) {
+func (kex *kexHybridSIDHp503X25519) keyAgreementClient(c *Conn, theirsKS keyShare, key []byte) ([]byte, error) {
 	var sharedKey [SIDHp503Curve25519SharedKeySz]byte
 	var ret []byte
 	var tmpKs keyShare
 
 	// Key agreement for classic
 	tmpKs.group = X25519
-	tmpKs.data = ks.data[:x25519SharedSecretSz]
-	ret, err := kex.classicKEX.keyAgreementClient(c, tmpKs, key[:x25519SharedSecretSz])
+	tmpKs.data = theirsKS.data[:x25519Sz]
+	ret, err := kex.classicKEX.keyAgreementClient(c, tmpKs, key[:x25519Sz])
 	if err != nil {
 		return nil, err
 	}
@@ -1330,11 +1345,157 @@ func (kex *kexHybridSIDHp503X25519) keyAgreementClient(c *Conn, ks keyShare, key
 
 	// Key agreement for PQ
 	tmpKs.group = 0 /*UNUSED*/
-	tmpKs.data = ks.data[x25519SharedSecretSz:]
-	ret, err = kex.pqKEX.keyAgreementClient(c, tmpKs, key[x25519SharedSecretSz:])
+	tmpKs.data = theirsKS.data[x25519Sz:]
+	ret, err = kex.pqKEX.keyAgreementClient(c, tmpKs, key[x25519Sz:])
 	if err != nil {
 		return nil, err
 	}
-	copy(sharedKey[x25519SharedSecretSz:], ret)
+	copy(sharedKey[x25519Sz:], ret)
 	return sharedKey[:], nil
 }
+
+// generate method generates SIKE key pair (ephemeral) on client side
+func (kexSIKEp503) generate(c *Conn, groupId CurveID) ([]byte, keyShare, error) {
+	if !c.isClient {
+		return nil, keyShare{}, errors.New("tls: internal error")
+	}
+
+	var prvKey = sidh.NewPrivateKey(sidh.FP_503, sidh.KeyVariant_SIKE)
+	if prvKey.Generate(c.config.rand()) != nil {
+		return nil, keyShare{}, errors.New("tls: private SIDH key generation failed")
+	}
+	var pubKey = prvKey.GeneratePublicKey()
+	var ks = keyShare{data: pubKey.Export()}
+
+	// 'buf' is a concatenation of (private || public) key. I need public key
+	// when decapsulating in kexSIKEp503::keyAgreementClient.
+	var buf = make([]byte, prvKey.Size()+pubKey.Size())
+	copy(buf, prvKey.Export())
+	copy(buf[prvKey.Size():], ks.data)
+	return buf, ks, nil
+}
+
+// keyAgreementClient performs KEM decapsulation. 'privateKey' is a concatenation
+// of (private || public) key
+func (kexSIKEp503) keyAgreementClient(c *Conn, theirsKS keyShare, privateKey []byte) ([]byte, error) {
+	// Import private key
+	var prvKey = sidh.NewPrivateKey(sidh.FP_503, sidh.KeyVariant_SIKE)
+	var pubKey = sidh.NewPublicKey(sidh.FP_503, sidh.KeyVariant_SIKE)
+
+	if len(privateKey) != prvKey.Size()+pubKey.Size() {
+		return nil, errors.New("tls: internal error")
+	}
+
+	// Never fails
+	prvKey.Import(privateKey[:prvKey.Size()])
+	pubKey.Import(privateKey[prvKey.Size():])
+
+	ss, err := sike.Decapsulate(prvKey, pubKey, theirsKS.data)
+	if err != nil {
+		return nil, err
+	}
+	return ss, nil
+}
+
+// keyAgreementServer performs KEM encapsulation.
+func (kexSIKEp503) keyAgreementServer(c *Conn, theirsKS keyShare) ([]byte, keyShare, error) {
+	pubKey := sidh.NewPublicKey(sidh.FP_503, sidh.KeyVariant_SIKE)
+	if pubKey.Import(theirsKS.data) != nil {
+		return nil, keyShare{}, errors.New("tls: can't import public SIKE key")
+	}
+	ct, key, err := sike.Encapsulate(c.config.rand(), pubKey)
+	if err != nil {
+		return nil, keyShare{}, errors.New("tls: SIKE encapsulation failed")
+	}
+	return key, keyShare{data: ct}, nil
+}
+
+// KEX Hybrid SIKEp503-X25519
+func (kex *kexHybridSIKEp503X25519) generate(c *Conn, groupId CurveID) ([]byte, keyShare, error) {
+	var pubHybrid [SIKEp503Curve25519PubKeySz]byte
+	var prvHybrid [SIKEp503Curve25519PrvKeySz + SIDHp503PubKeySz]byte
+
+	// Generate ephemeral key for classic x25519
+	private, ks, err := kex.classicKEX.generate(c, 0)
+	if err != nil {
+		return nil, keyShare{}, err
+	}
+	copy(prvHybrid[:], private)
+	copy(pubHybrid[:], ks.data)
+
+	// Generate PQ ephemeral key for SIDH
+	private, ks, err = kex.pqKEX.generate(c, 0)
+	if err != nil {
+		return nil, keyShare{}, err
+	}
+	copy(prvHybrid[x25519Sz:], private)
+	copy(pubHybrid[x25519Sz:], ks.data)
+	return prvHybrid[:], keyShare{group: HybridSIKEp503Curve25519, data: pubHybrid[:]}, nil
+}
+
+// keyAgreementClient performs X25519-SIKEp503 key agreement on client side. 'theirsKS.data' contains
+// X25519 public key and SIKEp503 KEM generated by the server. 'privateKey' is a key stored
+// locally by the process. It is a concatenation of (X25519 || SIKEp503 private || SIKEp503 public) keys.
+// In case of success concatenation of (X25519||SIKEp503) shared secrets is returned (32+16 bytes).
+func (kex *kexHybridSIKEp503X25519) keyAgreementClient(c *Conn, theirsKS keyShare, privateKey []byte) ([]byte, error) {
+	var ssHyb [SIKEp503Curve25519SharedKeySz]byte
+	var tmpKs keyShare
+
+	if len(privateKey) != SIKEp503Curve25519PrvKeySz+SIDHp503PubKeySz {
+		return nil, errors.New("tls: internal error")
+	}
+
+	if len(theirsKS.data) != SIKEp503Curve25519CtSz {
+		return nil, errors.New("tls: wrong key size for X25519-SIKEp503")
+	}
+
+	// Key agreement for classic
+	tmpKs.group = X25519
+	tmpKs.data = theirsKS.data[:x25519Sz]
+	ret, err := kex.classicKEX.keyAgreementClient(c, tmpKs, privateKey[:x25519Sz])
+	if err != nil {
+		return nil, err
+	}
+	copy(ssHyb[:], ret)
+
+	// Key agreement for PQ
+	tmpKs.group = 0 /*UNUSED*/
+	tmpKs.data = theirsKS.data[x25519Sz:]
+	ret, err = kex.pqKEX.keyAgreementClient(c, tmpKs, privateKey[x25519Sz:])
+	if err != nil {
+		return nil, err
+	}
+	copy(ssHyb[x25519Sz:], ret[:])
+	return ssHyb[:], nil
+}
+
+// keyAgreementServer performs X25519-SIKEp503 shared secret agreement on a server side. 'theirsKS'
+// contains concatenation of public keys for both X25519 and SIKEp503. In case of success
+// function returns X25519 and SIKEp503 shaerd secret concatenated together and concatenation of
+// X25519 public and SIKEp503 ciphertext that are sent to the client.
+func (kex *kexHybridSIKEp503X25519) keyAgreementServer(c *Conn, theirsKS keyShare) ([]byte, keyShare, error) {
+	var ssHyb [SIKEp503Curve25519SharedKeySz]byte
+	var ret [SIKEp503Curve25519CtSz]byte
+
+	if len(theirsKS.data) != SIKEp503Curve25519PubKeySz {
+		return nil, keyShare{}, errors.New("tls: wrong key size for X25519-SIKEp503")
+	}
+
+	var tmpKs = keyShare{group: X25519, data: theirsKS.data[:x25519Sz]}
+	ss, srvKs, err := kex.classicKEX.keyAgreementServer(c, tmpKs)
+	if err != nil {
+		return nil, keyShare{}, err
+	}
+	copy(ssHyb[:], ss[:])
+	copy(ret[:], srvKs.data[:])
+
+	tmpKs.group = 0 /*UNUSED*/
+	tmpKs.data = theirsKS.data[x25519Sz:]
+	ss, srvKs, err = kex.pqKEX.keyAgreementServer(c, tmpKs)
+	if err != nil {
+		return nil, keyShare{}, err
+	}
+	copy(ssHyb[x25519Sz:], ss[:])
+	copy(ret[x25519Sz:], srvKs.data[:SIKEp503CtSz])
+	return ssHyb[:], keyShare{group: HybridSIKEp503Curve25519, data: ret[:]}, nil
+}
diff --git a/_dev/interop_test_runner b/_dev/interop_test_runner
index c1de46d..5fe9577 100755
--- a/_dev/interop_test_runner
+++ b/_dev/interop_test_runner
@@ -292,6 +292,10 @@ class InteropServer_TRIS(ClientNominalMixin, InteropServer, unittest.TestCase):
         res = self.d.run_client(self.CLIENT_NAME, '-rsa=false -ecdsa=true -groups X25519-SIDHp503 '+self.server_ip+":7443")
         self.assertEqual(res[0], 0)
 
+    def test_SIKE(self):
+        res = self.d.run_client(self.CLIENT_NAME, '-rsa=false -ecdsa=true -groups X25519-SIKEp503 '+self.server_ip+":7443")
+        self.assertEqual(res[0], 0)
+
     def test_server_doesnt_support_SIDH(self):
         '''
         Client advertises HybridSIDH and ECDH. Server supports ECDH only. Checks weather
diff --git a/_dev/tris-localserver/runner.sh b/_dev/tris-localserver/runner.sh
index 32d1600..9b43013 100755
--- a/_dev/tris-localserver/runner.sh
+++ b/_dev/tris-localserver/runner.sh
@@ -6,6 +6,6 @@
 ./tris-localserver -b 0.0.0.0:4443 -cert=ecdsa -rtt0=oa 2>&1 &  # fourth port: offer and accept 0-RTT
 ./tris-localserver -b 0.0.0.0:5443 -cert=ecdsa -rtt0=oa -rtt0ack 2>&1 &  # fifth port: offer and accept 0-RTT but confirm
 ./tris-localserver -b 0.0.0.0:6443 -cert=rsa   -cliauth 2>&1 &  # sixth port: RSA with required client authentication
-./tris-localserver -b 0.0.0.0:7443 -cert=ecdsa -qr=c &          # Enables support for both - post-quantum and classical KEX algorithms
+./tris-localserver -b 0.0.0.0:7443 -cert=ecdsa -pq=c &          # Enables support for both - post-quantum and classical KEX algorithms
 
 wait
diff --git a/_dev/tris-localserver/server.go b/_dev/tris-localserver/server.go
index 23deafc..4c7733f 100644
--- a/_dev/tris-localserver/server.go
+++ b/_dev/tris-localserver/server.go
@@ -55,13 +55,13 @@ func NewServer() *server {
 	return s
 }
 
-func enableQR(s *server, enableDefault bool) {
-	var sidhCurves = []tls.CurveID{tls.HybridSIDHp503Curve25519}
+func enablePQ(s *server, enableDefault bool) {
+	var pqGroups = []tls.CurveID{tls.HybridSIDHp503Curve25519, tls.HybridSIKEp503Curve25519}
 	if enableDefault {
 		var defaultCurvePreferences = []tls.CurveID{tls.X25519, tls.CurveP256, tls.CurveP384, tls.CurveP521}
 		s.TLS.CurvePreferences = append(s.TLS.CurvePreferences, defaultCurvePreferences...)
 	}
-	s.TLS.CurvePreferences = append(s.TLS.CurvePreferences, sidhCurves...)
+	s.TLS.CurvePreferences = append(s.TLS.CurvePreferences, pqGroups...)
 }
 
 func (s *server) start() {
@@ -153,7 +153,7 @@ func main() {
 	arg_zerortt := flag.String("rtt0", "n", `0-RTT, accepts following values [n: None, a: Accept, o: Offer, oa: Offer and Accept]`)
 	arg_confirm := flag.Bool("rtt0ack", false, "0-RTT confirm")
 	arg_clientauth := flag.Bool("cliauth", false, "Performs client authentication (RequireAndVerifyClientCert used)")
-	arg_qr := flag.String("qr", "", "Enable quantum-resistant algorithms [c: Support classical and Quantum-Resistant, q: Enable Quantum-Resistant only]")
+	arg_pq := flag.String("pq", "", "Enable quantum-resistant algorithms [c: Support classical and Quantum-Resistant, q: Enable Quantum-Resistant only]")
 	flag.Parse()
 
 	s.Address = *arg_addr
@@ -172,10 +172,10 @@ func main() {
 		s.TLS.ClientAuth = tls.RequireAndVerifyClientCert
 	}
 
-	if *arg_qr == "c" {
-		enableQR(s, true)
-	} else if *arg_qr == "q" {
-		enableQR(s, false)
+	if *arg_pq == "c" {
+		enablePQ(s, true)
+	} else if *arg_pq == "q" {
+		enablePQ(s, false)
 	}
 
 	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
diff --git a/_dev/tris-testclient/client.go b/_dev/tris-testclient/client.go
index b54499b..a5efa76 100644
--- a/_dev/tris-testclient/client.go
+++ b/_dev/tris-testclient/client.go
@@ -29,6 +29,7 @@ var cipherSuiteIdToName = map[uint16]string{
 
 var namedGroupsToName = map[uint16]string{
 	uint16(tls.HybridSIDHp503Curve25519): "X25519-SIDHp503",
+	uint16(tls.HybridSIKEp503Curve25519): "X25519-SIKEp503",
 	uint16(tls.X25519):                   "X25519",
 	uint16(tls.CurveP256):                "P-256",
 	uint16(tls.CurveP384):                "P-384",
diff --git a/common.go b/common.go
index 459b1ef..8756e7b 100644
--- a/common.go
+++ b/common.go
@@ -124,6 +124,7 @@ const (
 
 	// Experimental KEX
 	HybridSIDHp503Curve25519 CurveID = 0xFE30
+	HybridSIKEp503Curve25519 CurveID = 0xFE32
 )
 
 // TLS 1.3 Key Share