diff --git a/crypto_stream_chacha20.js b/crypto_stream_chacha20.js
index 73b9b0b..2832d3a 100644
--- a/crypto_stream_chacha20.js
+++ b/crypto_stream_chacha20.js
@@ -1,6 +1,5 @@
 const assert = require('nanoassert')
-
-const constant = [1634760805, 857760878, 2036477234, 1797285236]
+const Chacha20 = require('chacha20-universal')
 
 exports.crypto_stream_chacha20_KEYBYTES = 32
 exports.crypto_stream_chacha20_NONCEBYTES = 8
@@ -81,139 +80,3 @@ exports.crypto_stream_chacha20_ietf_xor_instance = function (n, k) {
 
   return new Chacha20(n, k)
 }
-
-function Chacha20 (n, k, counter) {
-  assert(k.byteLength === exports.crypto_stream_chacha20_ietf_KEYBYTES)
-  assert(n.byteLength === exports.crypto_stream_chacha20_NONCEBYTES ||
-    n.byteLength === exports.crypto_stream_chacha20_ietf_NONCEBYTES)
-
-  if (!counter) counter = 0
-  assert(counter < Number.MAX_SAFE_INTEGER)
-
-  this.finalized = false
-  this.pos = 0
-  this.state = new Uint32Array(16)
-
-  for (let i = 0; i < 4; i++) this.state[i] = constant[i]
-  for (let i = 0; i < 8; i++) this.state[4 + i] = readUInt32LE(k, 4 * i)
-
-  this.state[12] = counter & 0xffffffff
-
-  if (n.byteLength === 8) {
-    this.state[13] = (counter && 0xffffffff00000000) >> 32
-    this.state[14] = readUInt32LE(n, 0)
-    this.state[15] = readUInt32LE(n, 4)
-  } else {
-    this.state[13] = readUInt32LE(n, 0)
-    this.state[14] = readUInt32LE(n, 4)
-    this.state[15] = readUInt32LE(n, 8)
-  }
-
-  return this
-}
-
-Chacha20.prototype.update = function (output, input) {
-  assert(!this.finalized, 'cipher finalized.')
-  assert(output.byteLength >= input.byteLength,
-    'output cannot be shorter than input.')
-
-  let len = input.length
-  let offset = this.pos % 64
-  this.pos += len
-
-  // input position
-  let j = 0
-
-  let keyStream = chacha20Block(this.state)
-
-  // try to finsih the current block
-  while (offset > 0 && len > 0) {
-    output[j] = input[j++] ^ keyStream[offset]
-    offset = (offset + 1) & 0x3f
-    if (!offset) this.state[12]++
-    len--
-  }
-
-  // encrypt rest block at a time
-  while (len > 0) {
-    keyStream = chacha20Block(this.state)
-
-    // less than a full block remaining
-    if (len < 64) {
-      for (let i = 0; i < len; i++) {
-        output[j] = input[j++] ^ keyStream[offset++]
-        offset &= 0x3f
-      }
-
-      return
-    }
-
-    for (; offset < 64;) {
-      output[j] = input[j++] ^ keyStream[offset++]
-    }
-
-    this.state[12]++
-    offset = 0
-    len -= 64
-  }
-}
-
-Chacha20.prototype.final = function () {
-  this.finalized = true
-}
-
-function chacha20Block (state) {
-  // working state
-  const ws = new Uint32Array(16)
-  for (let i = 16; i--;) ws[i] = state[i]
-
-  for (let i = 0; i < 20; i += 2) {
-    QR(ws, 0, 4, 8, 12) // column 0
-    QR(ws, 1, 5, 9, 13) // column 1
-    QR(ws, 2, 6, 10, 14) // column 2
-    QR(ws, 3, 7, 11, 15) // column 3
-
-    QR(ws, 0, 5, 10, 15) // diagonal 1 (main diagonal)
-    QR(ws, 1, 6, 11, 12) // diagonal 2
-    QR(ws, 2, 7, 8, 13) // diagonal 3
-    QR(ws, 3, 4, 9, 14) // diagonal 4
-  }
-
-  for (let i = 0; i < 16; i++) {
-    ws[i] += state[i]
-  }
-
-  return Buffer.from(ws.buffer, ws.byteOffset, ws.byteLength)
-}
-
-function rotl (a, b) {
-  return ((a << b) | (a >>> (32 - b)))
-}
-
-function QR (obj, a, b, c, d) {
-  obj[a] += obj[b]
-  obj[d] ^= obj[a]
-  obj[d] = rotl(obj[d], 16)
-
-  obj[c] += obj[d]
-  obj[b] ^= obj[c]
-  obj[b] = rotl(obj[b], 12)
-
-  obj[a] += obj[b]
-  obj[d] ^= obj[a]
-  obj[d] = rotl(obj[d], 8)
-
-  obj[c] += obj[d]
-  obj[b] ^= obj[c]
-  obj[b] = rotl(obj[b], 7)
-}
-
-function readUInt32LE (buf, offset) {
-  if (Buffer.isBuffer(buf)) return buf.readUInt32LE(offset)
-  else if (buf instanceof Uint8Array) {
-    var ret = 0
-    for (let i = 0; i < 4; i++) ret |= buf[offset + i] << (8 * i)
-    return ret
-  }
-  assert(false, 'buf should be a Buffer or a Uint8Array')
-}
diff --git a/package.json b/package.json
index 2919548..87fb2f9 100644
--- a/package.json
+++ b/package.json
@@ -5,6 +5,7 @@
   "main": "index.js",
   "dependencies": {
     "blake2b": "^2.1.1",
+    "chacha20-universal": "^1.0.2",
     "nanoassert": "^1.0.0",
     "siphash24": "^1.0.1",
     "xsalsa20": "^1.0.0"