diff --git a/cookie.go b/cookie.go
index e7c926a..8226ef0 100644
--- a/cookie.go
+++ b/cookie.go
@@ -8,7 +8,6 @@ package main
 import (
 	"crypto/hmac"
 	"crypto/rand"
-	"git.zx2c4.com/wireguard-go/xchacha20poly1305"
 	"golang.org/x/crypto/blake2s"
 	"golang.org/x/crypto/chacha20poly1305"
 	"sync"
@@ -163,13 +162,8 @@ func (st *CookieChecker) CreateReply(
 		return nil, err
 	}
 
-	xchacha20poly1305.Encrypt(
-		reply.Cookie[:0],
-		&reply.Nonce,
-		cookie[:],
-		msg[smac1:smac2],
-		&st.mac2.encryptionKey,
-	)
+	xchapoly, _ := chacha20poly1305.NewX(st.mac2.encryptionKey[:])
+	xchapoly.Seal(reply.Cookie[:0], reply.Nonce[:], cookie[:], msg[smac1:smac2])
 
 	st.mutex.RUnlock()
 
@@ -207,13 +201,8 @@ func (st *CookieGenerator) ConsumeReply(msg *MessageCookieReply) bool {
 
 	var cookie [blake2s.Size128]byte
 
-	_, err := xchacha20poly1305.Decrypt(
-		cookie[:0],
-		&msg.Nonce,
-		msg.Cookie[:],
-		st.mac2.lastMAC1[:],
-		&st.mac2.encryptionKey,
-	)
+	xchapoly, _ := chacha20poly1305.NewX(st.mac2.encryptionKey[:])
+	_, err := xchapoly.Open(cookie[:0], msg.Nonce[:], msg.Cookie[:], st.mac2.lastMAC1[:])
 
 	if err != nil {
 		return false
diff --git a/noise-protocol.go b/noise-protocol.go
index cc85cce..0686a11 100644
--- a/noise-protocol.go
+++ b/noise-protocol.go
@@ -89,7 +89,7 @@ type MessageTransport struct {
 type MessageCookieReply struct {
 	Type     uint32
 	Receiver uint32
-	Nonce    [24]byte
+	Nonce    [chacha20poly1305.NonceSizeX]byte
 	Cookie   [blake2s.Size128 + poly1305.TagSize]byte
 }
 
diff --git a/xchacha20poly1305/xchacha20.go b/xchacha20poly1305/xchacha20.go
deleted file mode 100644
index 412797d..0000000
--- a/xchacha20poly1305/xchacha20.go
+++ /dev/null
@@ -1,171 +0,0 @@
-/* SPDX-License-Identifier: MIT
- *
- * Copyright (C) 2016 Andreas Auernhammer. All Rights Reserved.
- * Copyright (C) 2017-2018 WireGuard LLC. All Rights Reserved.
- */
-
-package xchacha20poly1305
-
-import (
-	"encoding/binary"
-	"golang.org/x/crypto/chacha20poly1305"
-)
-
-func hChaCha20(out *[32]byte, nonce []byte, key *[32]byte) {
-
-	v00 := uint32(0x61707865)
-	v01 := uint32(0x3320646e)
-	v02 := uint32(0x79622d32)
-	v03 := uint32(0x6b206574)
-
-	v04 := binary.LittleEndian.Uint32(key[0:])
-	v05 := binary.LittleEndian.Uint32(key[4:])
-	v06 := binary.LittleEndian.Uint32(key[8:])
-	v07 := binary.LittleEndian.Uint32(key[12:])
-	v08 := binary.LittleEndian.Uint32(key[16:])
-	v09 := binary.LittleEndian.Uint32(key[20:])
-	v10 := binary.LittleEndian.Uint32(key[24:])
-	v11 := binary.LittleEndian.Uint32(key[28:])
-	v12 := binary.LittleEndian.Uint32(nonce[0:])
-	v13 := binary.LittleEndian.Uint32(nonce[4:])
-	v14 := binary.LittleEndian.Uint32(nonce[8:])
-	v15 := binary.LittleEndian.Uint32(nonce[12:])
-
-	for i := 0; i < 20; i += 2 {
-		v00 += v04
-		v12 ^= v00
-		v12 = (v12 << 16) | (v12 >> 16)
-		v08 += v12
-		v04 ^= v08
-		v04 = (v04 << 12) | (v04 >> 20)
-		v00 += v04
-		v12 ^= v00
-		v12 = (v12 << 8) | (v12 >> 24)
-		v08 += v12
-		v04 ^= v08
-		v04 = (v04 << 7) | (v04 >> 25)
-		v01 += v05
-		v13 ^= v01
-		v13 = (v13 << 16) | (v13 >> 16)
-		v09 += v13
-		v05 ^= v09
-		v05 = (v05 << 12) | (v05 >> 20)
-		v01 += v05
-		v13 ^= v01
-		v13 = (v13 << 8) | (v13 >> 24)
-		v09 += v13
-		v05 ^= v09
-		v05 = (v05 << 7) | (v05 >> 25)
-		v02 += v06
-		v14 ^= v02
-		v14 = (v14 << 16) | (v14 >> 16)
-		v10 += v14
-		v06 ^= v10
-		v06 = (v06 << 12) | (v06 >> 20)
-		v02 += v06
-		v14 ^= v02
-		v14 = (v14 << 8) | (v14 >> 24)
-		v10 += v14
-		v06 ^= v10
-		v06 = (v06 << 7) | (v06 >> 25)
-		v03 += v07
-		v15 ^= v03
-		v15 = (v15 << 16) | (v15 >> 16)
-		v11 += v15
-		v07 ^= v11
-		v07 = (v07 << 12) | (v07 >> 20)
-		v03 += v07
-		v15 ^= v03
-		v15 = (v15 << 8) | (v15 >> 24)
-		v11 += v15
-		v07 ^= v11
-		v07 = (v07 << 7) | (v07 >> 25)
-		v00 += v05
-		v15 ^= v00
-		v15 = (v15 << 16) | (v15 >> 16)
-		v10 += v15
-		v05 ^= v10
-		v05 = (v05 << 12) | (v05 >> 20)
-		v00 += v05
-		v15 ^= v00
-		v15 = (v15 << 8) | (v15 >> 24)
-		v10 += v15
-		v05 ^= v10
-		v05 = (v05 << 7) | (v05 >> 25)
-		v01 += v06
-		v12 ^= v01
-		v12 = (v12 << 16) | (v12 >> 16)
-		v11 += v12
-		v06 ^= v11
-		v06 = (v06 << 12) | (v06 >> 20)
-		v01 += v06
-		v12 ^= v01
-		v12 = (v12 << 8) | (v12 >> 24)
-		v11 += v12
-		v06 ^= v11
-		v06 = (v06 << 7) | (v06 >> 25)
-		v02 += v07
-		v13 ^= v02
-		v13 = (v13 << 16) | (v13 >> 16)
-		v08 += v13
-		v07 ^= v08
-		v07 = (v07 << 12) | (v07 >> 20)
-		v02 += v07
-		v13 ^= v02
-		v13 = (v13 << 8) | (v13 >> 24)
-		v08 += v13
-		v07 ^= v08
-		v07 = (v07 << 7) | (v07 >> 25)
-		v03 += v04
-		v14 ^= v03
-		v14 = (v14 << 16) | (v14 >> 16)
-		v09 += v14
-		v04 ^= v09
-		v04 = (v04 << 12) | (v04 >> 20)
-		v03 += v04
-		v14 ^= v03
-		v14 = (v14 << 8) | (v14 >> 24)
-		v09 += v14
-		v04 ^= v09
-		v04 = (v04 << 7) | (v04 >> 25)
-	}
-
-	binary.LittleEndian.PutUint32(out[0:], v00)
-	binary.LittleEndian.PutUint32(out[4:], v01)
-	binary.LittleEndian.PutUint32(out[8:], v02)
-	binary.LittleEndian.PutUint32(out[12:], v03)
-	binary.LittleEndian.PutUint32(out[16:], v12)
-	binary.LittleEndian.PutUint32(out[20:], v13)
-	binary.LittleEndian.PutUint32(out[24:], v14)
-	binary.LittleEndian.PutUint32(out[28:], v15)
-}
-
-func Encrypt(
-	dst []byte,
-	nonceFull *[24]byte,
-	plaintext []byte,
-	additionalData []byte,
-	key *[chacha20poly1305.KeySize]byte,
-) []byte {
-	var nonce [chacha20poly1305.NonceSize]byte
-	var derivedKey [chacha20poly1305.KeySize]byte
-	hChaCha20(&derivedKey, nonceFull[:16], key)
-	aead, _ := chacha20poly1305.New(derivedKey[:])
-	copy(nonce[4:], nonceFull[16:])
-	return aead.Seal(dst, nonce[:], plaintext, additionalData)
-}
-
-func Decrypt(
-	dst []byte,
-	nonceFull *[24]byte,
-	plaintext []byte,
-	additionalData []byte,
-	key *[chacha20poly1305.KeySize]byte,
-) ([]byte, error) {
-	var nonce [chacha20poly1305.NonceSize]byte
-	var derivedKey [chacha20poly1305.KeySize]byte
-	hChaCha20(&derivedKey, nonceFull[:16], key)
-	aead, _ := chacha20poly1305.New(derivedKey[:])
-	copy(nonce[4:], nonceFull[16:])
-	return aead.Open(dst, nonce[:], plaintext, additionalData)
-}
diff --git a/xchacha20poly1305/xchacha20_test.go b/xchacha20poly1305/xchacha20_test.go
deleted file mode 100644
index 0c3a80d..0000000
--- a/xchacha20poly1305/xchacha20_test.go
+++ /dev/null
@@ -1,101 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0
- *
- * Copyright (C) 2017-2018 WireGuard LLC. All Rights Reserved.
- */
-
-package xchacha20poly1305
-
-import (
-	"encoding/hex"
-	"testing"
-)
-
-type XChaCha20Test struct {
-	Nonce string
-	Key   string
-	PT    string
-	CT    string
-}
-
-func TestXChaCha20(t *testing.T) {
-
-	tests := []XChaCha20Test{
-		{
-			Nonce: "000000000000000000000000000000000000000000000000",
-			Key:   "0000000000000000000000000000000000000000000000000000000000000000",
-			PT:    "00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000",
-			CT:    "789e9689e5208d7fd9e1f3c5b5341f48ef18a13e418998addadd97a3693a987f8e82ecd5c1433bfed1af49750c0f1ff29c4174a05b119aa3a9e8333812e0c0feb1299c5949d895ee01dbf50f8395dd84",
-		},
-		{
-			Nonce: "0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f",
-			Key:   "0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f",
-			PT:    "0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f",
-			CT:    "e1a046aa7f71e2af8b80b6408b2fd8d3a350278cde79c94d9efaa475e1339b3dd490127b",
-		},
-		{
-			Nonce: "d9a8213e8a697508805c2c171ad54487ead9e3e02d82d5bc",
-			Key:   "979196dbd78526f2f584f7534db3f5824d8ccfa858ca7e09bdd3656ecd36033c",
-			PT:    "43cc6d624e451bbed952c3e071dc6c03392ce11eb14316a94b2fdc98b22fedea",
-			CT:    "53c1e8bef2dbb8f2505ec010a7afe21d5a8e6dd8f987e4ea1a2ed5dfbc844ea400db34496fd2153526c6e87c36694200",
-		},
-	}
-
-	for _, test := range tests {
-
-		nonce, err := hex.DecodeString(test.Nonce)
-		if err != nil {
-			panic(err)
-		}
-
-		key, err := hex.DecodeString(test.Key)
-		if err != nil {
-			panic(err)
-		}
-
-		pt, err := hex.DecodeString(test.PT)
-		if err != nil {
-			panic(err)
-		}
-
-		func() {
-			var nonceArray [24]byte
-			var keyArray [32]byte
-			copy(nonceArray[:], nonce)
-			copy(keyArray[:], key)
-
-			// test encryption
-
-			ct := Encrypt(
-				nil,
-				&nonceArray,
-				pt,
-				nil,
-				&keyArray,
-			)
-			ctHex := hex.EncodeToString(ct)
-			if ctHex != test.CT {
-				t.Fatal("encryption failed, expected:", test.CT, "got", ctHex)
-			}
-
-			// test decryption
-
-			ptp, err := Decrypt(
-				nil,
-				&nonceArray,
-				ct,
-				nil,
-				&keyArray,
-			)
-			if err != nil {
-				t.Fatal(err)
-			}
-
-			ptHex := hex.EncodeToString(ptp)
-			if ptHex != test.PT {
-				t.Fatal("decryption failed, expected:", test.PT, "got", ptHex)
-			}
-		}()
-
-	}
-
-}