diff --git a/.gitignore b/.gitignore
index de038d6..9b18914 100644
--- a/.gitignore
+++ b/.gitignore
@@ -4,3 +4,6 @@ build
 node_modules
 
 npm-debug.log
+package-lock.json
+yarn-error.log
+yarn.lock
diff --git a/.travis.yml b/.travis.yml
index bfbdfc8..319dffc 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -4,10 +4,13 @@ os:
   - osx
 language: node_js
 node_js:
+  - "5"
   - "6"
   - "8"
   - "10"
   - "11"
+  - "12"
+  - "13"
 addons:
   apt:
     sources:
diff --git a/appveyor.yml b/appveyor.yml
index 175bb2d..7b49515 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -3,11 +3,11 @@ build: off
 skip_tags: true
 environment:
   matrix:
-    - nodejs_version: "4"
-    - nodejs_version: "5"
     - nodejs_version: "6"
     - nodejs_version: "7"
     - nodejs_version: "8"
+    - nodejs_version: "10"
+    - nodejs_version: "12"
 platform:
   - x86
   - x64
diff --git a/lib/api/index.js b/lib/api/index.js
index a91ab19..b014e91 100644
--- a/lib/api/index.js
+++ b/lib/api/index.js
@@ -1,13 +1,13 @@
 'use strict'
-var createKeccak = require('./keccak')
-var createShake = require('./shake')
+const createKeccak = require('./keccak')
+const createShake = require('./shake')
 
 module.exports = function (KeccakState) {
-  var Keccak = createKeccak(KeccakState)
-  var Shake = createShake(KeccakState)
+  const Keccak = createKeccak(KeccakState)
+  const Shake = createShake(KeccakState)
 
   return function (algorithm, options) {
-    var hash = typeof algorithm === 'string' ? algorithm.toLowerCase() : algorithm
+    const hash = typeof algorithm === 'string' ? algorithm.toLowerCase() : algorithm
     switch (hash) {
       case 'keccak224': return new Keccak(1152, 448, null, 224, options)
       case 'keccak256': return new Keccak(1088, 512, null, 256, options)
diff --git a/lib/api/keccak.js b/lib/api/keccak.js
index fe384e3..26053c5 100644
--- a/lib/api/keccak.js
+++ b/lib/api/keccak.js
@@ -1,7 +1,7 @@
 'use strict'
-var Buffer = require('safe-buffer').Buffer
-var Transform = require('stream').Transform
-var inherits = require('inherits')
+const Buffer = require('safe-buffer').Buffer
+const Transform = require('stream').Transform
+const inherits = require('inherits')
 
 module.exports = function (KeccakState) {
   function Keccak (rate, capacity, delimitedSuffix, hashBitLength, options) {
@@ -21,7 +21,7 @@ module.exports = function (KeccakState) {
   inherits(Keccak, Transform)
 
   Keccak.prototype._transform = function (chunk, encoding, callback) {
-    var error = null
+    let error = null
     try {
       this.update(chunk, encoding)
     } catch (err) {
@@ -32,7 +32,7 @@ module.exports = function (KeccakState) {
   }
 
   Keccak.prototype._flush = function (callback) {
-    var error = null
+    let error = null
     try {
       this.push(this.digest())
     } catch (err) {
@@ -57,7 +57,7 @@ module.exports = function (KeccakState) {
     this._finalized = true
 
     if (this._delimitedSuffix) this._state.absorbLastFewBits(this._delimitedSuffix)
-    var digest = this._state.squeeze(this._hashBitLength / 8)
+    let digest = this._state.squeeze(this._hashBitLength / 8)
     if (encoding !== undefined) digest = digest.toString(encoding)
 
     this._resetState()
@@ -73,7 +73,7 @@ module.exports = function (KeccakState) {
 
   // because sometimes we need hash right now and little later
   Keccak.prototype._clone = function () {
-    var clone = new Keccak(this._rate, this._capacity, this._delimitedSuffix, this._hashBitLength, this._options)
+    const clone = new Keccak(this._rate, this._capacity, this._delimitedSuffix, this._hashBitLength, this._options)
     this._state.copy(clone._state)
     clone._finalized = this._finalized
 
diff --git a/lib/api/shake.js b/lib/api/shake.js
index 103d802..c8d6a96 100644
--- a/lib/api/shake.js
+++ b/lib/api/shake.js
@@ -1,7 +1,7 @@
 'use strict'
-var Buffer = require('safe-buffer').Buffer
-var Transform = require('stream').Transform
-var inherits = require('inherits')
+const Buffer = require('safe-buffer').Buffer
+const Transform = require('stream').Transform
+const inherits = require('inherits')
 
 module.exports = function (KeccakState) {
   function Shake (rate, capacity, delimitedSuffix, options) {
@@ -20,7 +20,7 @@ module.exports = function (KeccakState) {
   inherits(Shake, Transform)
 
   Shake.prototype._transform = function (chunk, encoding, callback) {
-    var error = null
+    let error = null
     try {
       this.update(chunk, encoding)
     } catch (err) {
@@ -52,7 +52,7 @@ module.exports = function (KeccakState) {
       this._state.absorbLastFewBits(this._delimitedSuffix)
     }
 
-    var data = this._state.squeeze(dataByteLength)
+    let data = this._state.squeeze(dataByteLength)
     if (encoding !== undefined) data = data.toString(encoding)
 
     return data
@@ -64,7 +64,7 @@ module.exports = function (KeccakState) {
   }
 
   Shake.prototype._clone = function () {
-    var clone = new Shake(this._rate, this._capacity, this._delimitedSuffix, this._options)
+    const clone = new Shake(this._rate, this._capacity, this._delimitedSuffix, this._options)
     this._state.copy(clone._state)
     clone._finalized = this._finalized
 
diff --git a/lib/keccak-state-reference.js b/lib/keccak-state-reference.js
index 1694534..d6918e7 100644
--- a/lib/keccak-state-reference.js
+++ b/lib/keccak-state-reference.js
@@ -1,6 +1,6 @@
 'use strict'
-var P1600_RHO_OFFSETS = [0, 1, 62, 28, 27, 36, 44, 6, 55, 20, 3, 10, 43, 25, 39, 41, 45, 15, 21, 8, 18, 2, 61, 56, 14]
-var P1600_ROUND_CONSTANTS = [
+const P1600_RHO_OFFSETS = [0, 1, 62, 28, 27, 36, 44, 6, 55, 20, 3, 10, 43, 25, 39, 41, 45, 15, 21, 8, 18, 2, 61, 56, 14]
+const P1600_ROUND_CONSTANTS = [
   0x00000001, 0x00000000,
   0x00008082, 0x00000000,
   0x0000808a, 0x80000000,
@@ -28,7 +28,7 @@ var P1600_ROUND_CONSTANTS = [
 ]
 
 function p1600 (state) {
-  for (var round = 0; round < 24; ++round) {
+  for (let round = 0; round < 24; ++round) {
     theta(state)
     rho(state)
     pi(state)
@@ -39,23 +39,23 @@ function p1600 (state) {
 
 // steps
 function theta (s) {
-  var clo = [0, 0, 0, 0, 0]
-  var chi = [0, 0, 0, 0, 0]
+  const clo = [0, 0, 0, 0, 0]
+  const chi = [0, 0, 0, 0, 0]
 
-  for (var x = 0; x < 5; ++x) {
-    for (var y = 0; y < 5; ++y) {
+  for (let x = 0; x < 5; ++x) {
+    for (let y = 0; y < 5; ++y) {
       clo[x] ^= s[ilo(x, y)]
       chi[x] ^= s[ihi(x, y)]
     }
   }
 
-  for (x = 0; x < 5; ++x) {
-    var next = (x + 1) % 5
-    var prev = (x + 4) % 5
-    var dlo = rol64lo(clo[next], chi[next], 1) ^ clo[prev]
-    var dhi = rol64hi(clo[next], chi[next], 1) ^ chi[prev]
+  for (let x = 0; x < 5; ++x) {
+    const next = (x + 1) % 5
+    const prev = (x + 4) % 5
+    const dlo = rol64lo(clo[next], chi[next], 1) ^ clo[prev]
+    const dhi = rol64hi(clo[next], chi[next], 1) ^ chi[prev]
 
-    for (y = 0; y < 5; ++y) {
+    for (let y = 0; y < 5; ++y) {
       s[ilo(x, y)] ^= dlo
       s[ihi(x, y)] ^= dhi
     }
@@ -63,10 +63,10 @@ function theta (s) {
 }
 
 function rho (s) {
-  for (var x = 0; x < 5; ++x) {
-    for (var y = 0; y < 5; ++y) {
-      var lo = rol64lo(s[ilo(x, y)], s[ihi(x, y)], P1600_RHO_OFFSETS[index(x, y)])
-      var hi = rol64hi(s[ilo(x, y)], s[ihi(x, y)], P1600_RHO_OFFSETS[index(x, y)])
+  for (let x = 0; x < 5; ++x) {
+    for (let y = 0; y < 5; ++y) {
+      const lo = rol64lo(s[ilo(x, y)], s[ihi(x, y)], P1600_RHO_OFFSETS[index(x, y)])
+      const hi = rol64hi(s[ilo(x, y)], s[ihi(x, y)], P1600_RHO_OFFSETS[index(x, y)])
       s[ilo(x, y)] = lo
       s[ihi(x, y)] = hi
     }
@@ -74,12 +74,12 @@ function rho (s) {
 }
 
 function pi (s) {
-  var ts = s.slice()
+  const ts = s.slice()
 
-  for (var x = 0; x < 5; ++x) {
-    for (var y = 0; y < 5; ++y) {
-      var nx = (0 * x + 1 * y) % 5
-      var ny = (2 * x + 3 * y) % 5
+  for (let x = 0; x < 5; ++x) {
+    for (let y = 0; y < 5; ++y) {
+      const nx = (0 * x + 1 * y) % 5
+      const ny = (2 * x + 3 * y) % 5
       s[ilo(nx, ny)] = ts[ilo(x, y)]
       s[ihi(nx, ny)] = ts[ihi(x, y)]
     }
@@ -87,16 +87,16 @@ function pi (s) {
 }
 
 function chi (s) {
-  var clo = [0, 0, 0, 0, 0]
-  var chi = [0, 0, 0, 0, 0]
+  const clo = [0, 0, 0, 0, 0]
+  const chi = [0, 0, 0, 0, 0]
 
-  for (var y = 0; y < 5; ++y) {
-    for (var x = 0; x < 5; ++x) {
+  for (let y = 0; y < 5; ++y) {
+    for (let x = 0; x < 5; ++x) {
       clo[x] = s[ilo(x, y)] ^ (~s[ilo((x + 1) % 5, y)] & s[ilo((x + 2) % 5, y)])
       chi[x] = s[ihi(x, y)] ^ (~s[ihi((x + 1) % 5, y)] & s[ihi((x + 2) % 5, y)])
     }
 
-    for (x = 0; x < 5; ++x) {
+    for (let x = 0; x < 5; ++x) {
       s[ilo(x, y)] = clo[x]
       s[ihi(x, y)] = chi[x]
     }
@@ -115,7 +115,7 @@ function ihi (x, y) { return index(x, y) * 2 + 1 }
 
 function rol64lo (lo, hi, shift) {
   if (shift >= 32) {
-    var t = lo
+    const t = lo
     lo = hi
     hi = t
     shift -= 32
@@ -126,7 +126,7 @@ function rol64lo (lo, hi, shift) {
 
 function rol64hi (lo, hi, shift) {
   if (shift >= 32) {
-    var t = lo
+    const t = lo
     lo = hi
     hi = t
     shift -= 32
diff --git a/lib/keccak-state-unroll.js b/lib/keccak-state-unroll.js
index 5732e95..790bdf4 100644
--- a/lib/keccak-state-unroll.js
+++ b/lib/keccak-state-unroll.js
@@ -1,132 +1,132 @@
 'use strict'
-var P1600_ROUND_CONSTANTS = [1, 0, 32898, 0, 32906, 2147483648, 2147516416, 2147483648, 32907, 0, 2147483649, 0, 2147516545, 2147483648, 32777, 2147483648, 138, 0, 136, 0, 2147516425, 0, 2147483658, 0, 2147516555, 0, 139, 2147483648, 32905, 2147483648, 32771, 2147483648, 32770, 2147483648, 128, 2147483648, 32778, 0, 2147483658, 2147483648, 2147516545, 2147483648, 32896, 2147483648, 2147483649, 0, 2147516424, 2147483648]
+const P1600_ROUND_CONSTANTS = [1, 0, 32898, 0, 32906, 2147483648, 2147516416, 2147483648, 32907, 0, 2147483649, 0, 2147516545, 2147483648, 32777, 2147483648, 138, 0, 136, 0, 2147516425, 0, 2147483658, 0, 2147516555, 0, 139, 2147483648, 32905, 2147483648, 32771, 2147483648, 32770, 2147483648, 128, 2147483648, 32778, 0, 2147483658, 2147483648, 2147516545, 2147483648, 32896, 2147483648, 2147483649, 0, 2147516424, 2147483648]
 
 exports.p1600 = function (s) {
-  for (var round = 0; round < 24; ++round) {
+  for (let round = 0; round < 24; ++round) {
     // theta
-    var lo0 = s[0] ^ s[10] ^ s[20] ^ s[30] ^ s[40]
-    var hi0 = s[1] ^ s[11] ^ s[21] ^ s[31] ^ s[41]
-    var lo1 = s[2] ^ s[12] ^ s[22] ^ s[32] ^ s[42]
-    var hi1 = s[3] ^ s[13] ^ s[23] ^ s[33] ^ s[43]
-    var lo2 = s[4] ^ s[14] ^ s[24] ^ s[34] ^ s[44]
-    var hi2 = s[5] ^ s[15] ^ s[25] ^ s[35] ^ s[45]
-    var lo3 = s[6] ^ s[16] ^ s[26] ^ s[36] ^ s[46]
-    var hi3 = s[7] ^ s[17] ^ s[27] ^ s[37] ^ s[47]
-    var lo4 = s[8] ^ s[18] ^ s[28] ^ s[38] ^ s[48]
-    var hi4 = s[9] ^ s[19] ^ s[29] ^ s[39] ^ s[49]
+    const lo0 = s[0] ^ s[10] ^ s[20] ^ s[30] ^ s[40]
+    const hi0 = s[1] ^ s[11] ^ s[21] ^ s[31] ^ s[41]
+    const lo1 = s[2] ^ s[12] ^ s[22] ^ s[32] ^ s[42]
+    const hi1 = s[3] ^ s[13] ^ s[23] ^ s[33] ^ s[43]
+    const lo2 = s[4] ^ s[14] ^ s[24] ^ s[34] ^ s[44]
+    const hi2 = s[5] ^ s[15] ^ s[25] ^ s[35] ^ s[45]
+    const lo3 = s[6] ^ s[16] ^ s[26] ^ s[36] ^ s[46]
+    const hi3 = s[7] ^ s[17] ^ s[27] ^ s[37] ^ s[47]
+    const lo4 = s[8] ^ s[18] ^ s[28] ^ s[38] ^ s[48]
+    const hi4 = s[9] ^ s[19] ^ s[29] ^ s[39] ^ s[49]
 
-    var lo = lo4 ^ (lo1 << 1 | hi1 >>> 31)
-    var hi = hi4 ^ (hi1 << 1 | lo1 >>> 31)
-    var t1slo0 = s[0] ^ lo
-    var t1shi0 = s[1] ^ hi
-    var t1slo5 = s[10] ^ lo
-    var t1shi5 = s[11] ^ hi
-    var t1slo10 = s[20] ^ lo
-    var t1shi10 = s[21] ^ hi
-    var t1slo15 = s[30] ^ lo
-    var t1shi15 = s[31] ^ hi
-    var t1slo20 = s[40] ^ lo
-    var t1shi20 = s[41] ^ hi
+    let lo = lo4 ^ (lo1 << 1 | hi1 >>> 31)
+    let hi = hi4 ^ (hi1 << 1 | lo1 >>> 31)
+    const t1slo0 = s[0] ^ lo
+    const t1shi0 = s[1] ^ hi
+    const t1slo5 = s[10] ^ lo
+    const t1shi5 = s[11] ^ hi
+    const t1slo10 = s[20] ^ lo
+    const t1shi10 = s[21] ^ hi
+    const t1slo15 = s[30] ^ lo
+    const t1shi15 = s[31] ^ hi
+    const t1slo20 = s[40] ^ lo
+    const t1shi20 = s[41] ^ hi
     lo = lo0 ^ (lo2 << 1 | hi2 >>> 31)
     hi = hi0 ^ (hi2 << 1 | lo2 >>> 31)
-    var t1slo1 = s[2] ^ lo
-    var t1shi1 = s[3] ^ hi
-    var t1slo6 = s[12] ^ lo
-    var t1shi6 = s[13] ^ hi
-    var t1slo11 = s[22] ^ lo
-    var t1shi11 = s[23] ^ hi
-    var t1slo16 = s[32] ^ lo
-    var t1shi16 = s[33] ^ hi
-    var t1slo21 = s[42] ^ lo
-    var t1shi21 = s[43] ^ hi
+    const t1slo1 = s[2] ^ lo
+    const t1shi1 = s[3] ^ hi
+    const t1slo6 = s[12] ^ lo
+    const t1shi6 = s[13] ^ hi
+    const t1slo11 = s[22] ^ lo
+    const t1shi11 = s[23] ^ hi
+    const t1slo16 = s[32] ^ lo
+    const t1shi16 = s[33] ^ hi
+    const t1slo21 = s[42] ^ lo
+    const t1shi21 = s[43] ^ hi
     lo = lo1 ^ (lo3 << 1 | hi3 >>> 31)
     hi = hi1 ^ (hi3 << 1 | lo3 >>> 31)
-    var t1slo2 = s[4] ^ lo
-    var t1shi2 = s[5] ^ hi
-    var t1slo7 = s[14] ^ lo
-    var t1shi7 = s[15] ^ hi
-    var t1slo12 = s[24] ^ lo
-    var t1shi12 = s[25] ^ hi
-    var t1slo17 = s[34] ^ lo
-    var t1shi17 = s[35] ^ hi
-    var t1slo22 = s[44] ^ lo
-    var t1shi22 = s[45] ^ hi
+    const t1slo2 = s[4] ^ lo
+    const t1shi2 = s[5] ^ hi
+    const t1slo7 = s[14] ^ lo
+    const t1shi7 = s[15] ^ hi
+    const t1slo12 = s[24] ^ lo
+    const t1shi12 = s[25] ^ hi
+    const t1slo17 = s[34] ^ lo
+    const t1shi17 = s[35] ^ hi
+    const t1slo22 = s[44] ^ lo
+    const t1shi22 = s[45] ^ hi
     lo = lo2 ^ (lo4 << 1 | hi4 >>> 31)
     hi = hi2 ^ (hi4 << 1 | lo4 >>> 31)
-    var t1slo3 = s[6] ^ lo
-    var t1shi3 = s[7] ^ hi
-    var t1slo8 = s[16] ^ lo
-    var t1shi8 = s[17] ^ hi
-    var t1slo13 = s[26] ^ lo
-    var t1shi13 = s[27] ^ hi
-    var t1slo18 = s[36] ^ lo
-    var t1shi18 = s[37] ^ hi
-    var t1slo23 = s[46] ^ lo
-    var t1shi23 = s[47] ^ hi
+    const t1slo3 = s[6] ^ lo
+    const t1shi3 = s[7] ^ hi
+    const t1slo8 = s[16] ^ lo
+    const t1shi8 = s[17] ^ hi
+    const t1slo13 = s[26] ^ lo
+    const t1shi13 = s[27] ^ hi
+    const t1slo18 = s[36] ^ lo
+    const t1shi18 = s[37] ^ hi
+    const t1slo23 = s[46] ^ lo
+    const t1shi23 = s[47] ^ hi
     lo = lo3 ^ (lo0 << 1 | hi0 >>> 31)
     hi = hi3 ^ (hi0 << 1 | lo0 >>> 31)
-    var t1slo4 = s[8] ^ lo
-    var t1shi4 = s[9] ^ hi
-    var t1slo9 = s[18] ^ lo
-    var t1shi9 = s[19] ^ hi
-    var t1slo14 = s[28] ^ lo
-    var t1shi14 = s[29] ^ hi
-    var t1slo19 = s[38] ^ lo
-    var t1shi19 = s[39] ^ hi
-    var t1slo24 = s[48] ^ lo
-    var t1shi24 = s[49] ^ hi
+    const t1slo4 = s[8] ^ lo
+    const t1shi4 = s[9] ^ hi
+    const t1slo9 = s[18] ^ lo
+    const t1shi9 = s[19] ^ hi
+    const t1slo14 = s[28] ^ lo
+    const t1shi14 = s[29] ^ hi
+    const t1slo19 = s[38] ^ lo
+    const t1shi19 = s[39] ^ hi
+    const t1slo24 = s[48] ^ lo
+    const t1shi24 = s[49] ^ hi
 
     // rho & pi
-    var t2slo0 = t1slo0
-    var t2shi0 = t1shi0
-    var t2slo16 = (t1shi5 << 4 | t1slo5 >>> 28)
-    var t2shi16 = (t1slo5 << 4 | t1shi5 >>> 28)
-    var t2slo7 = (t1slo10 << 3 | t1shi10 >>> 29)
-    var t2shi7 = (t1shi10 << 3 | t1slo10 >>> 29)
-    var t2slo23 = (t1shi15 << 9 | t1slo15 >>> 23)
-    var t2shi23 = (t1slo15 << 9 | t1shi15 >>> 23)
-    var t2slo14 = (t1slo20 << 18 | t1shi20 >>> 14)
-    var t2shi14 = (t1shi20 << 18 | t1slo20 >>> 14)
-    var t2slo10 = (t1slo1 << 1 | t1shi1 >>> 31)
-    var t2shi10 = (t1shi1 << 1 | t1slo1 >>> 31)
-    var t2slo1 = (t1shi6 << 12 | t1slo6 >>> 20)
-    var t2shi1 = (t1slo6 << 12 | t1shi6 >>> 20)
-    var t2slo17 = (t1slo11 << 10 | t1shi11 >>> 22)
-    var t2shi17 = (t1shi11 << 10 | t1slo11 >>> 22)
-    var t2slo8 = (t1shi16 << 13 | t1slo16 >>> 19)
-    var t2shi8 = (t1slo16 << 13 | t1shi16 >>> 19)
-    var t2slo24 = (t1slo21 << 2 | t1shi21 >>> 30)
-    var t2shi24 = (t1shi21 << 2 | t1slo21 >>> 30)
-    var t2slo20 = (t1shi2 << 30 | t1slo2 >>> 2)
-    var t2shi20 = (t1slo2 << 30 | t1shi2 >>> 2)
-    var t2slo11 = (t1slo7 << 6 | t1shi7 >>> 26)
-    var t2shi11 = (t1shi7 << 6 | t1slo7 >>> 26)
-    var t2slo2 = (t1shi12 << 11 | t1slo12 >>> 21)
-    var t2shi2 = (t1slo12 << 11 | t1shi12 >>> 21)
-    var t2slo18 = (t1slo17 << 15 | t1shi17 >>> 17)
-    var t2shi18 = (t1shi17 << 15 | t1slo17 >>> 17)
-    var t2slo9 = (t1shi22 << 29 | t1slo22 >>> 3)
-    var t2shi9 = (t1slo22 << 29 | t1shi22 >>> 3)
-    var t2slo5 = (t1slo3 << 28 | t1shi3 >>> 4)
-    var t2shi5 = (t1shi3 << 28 | t1slo3 >>> 4)
-    var t2slo21 = (t1shi8 << 23 | t1slo8 >>> 9)
-    var t2shi21 = (t1slo8 << 23 | t1shi8 >>> 9)
-    var t2slo12 = (t1slo13 << 25 | t1shi13 >>> 7)
-    var t2shi12 = (t1shi13 << 25 | t1slo13 >>> 7)
-    var t2slo3 = (t1slo18 << 21 | t1shi18 >>> 11)
-    var t2shi3 = (t1shi18 << 21 | t1slo18 >>> 11)
-    var t2slo19 = (t1shi23 << 24 | t1slo23 >>> 8)
-    var t2shi19 = (t1slo23 << 24 | t1shi23 >>> 8)
-    var t2slo15 = (t1slo4 << 27 | t1shi4 >>> 5)
-    var t2shi15 = (t1shi4 << 27 | t1slo4 >>> 5)
-    var t2slo6 = (t1slo9 << 20 | t1shi9 >>> 12)
-    var t2shi6 = (t1shi9 << 20 | t1slo9 >>> 12)
-    var t2slo22 = (t1shi14 << 7 | t1slo14 >>> 25)
-    var t2shi22 = (t1slo14 << 7 | t1shi14 >>> 25)
-    var t2slo13 = (t1slo19 << 8 | t1shi19 >>> 24)
-    var t2shi13 = (t1shi19 << 8 | t1slo19 >>> 24)
-    var t2slo4 = (t1slo24 << 14 | t1shi24 >>> 18)
-    var t2shi4 = (t1shi24 << 14 | t1slo24 >>> 18)
+    const t2slo0 = t1slo0
+    const t2shi0 = t1shi0
+    const t2slo16 = (t1shi5 << 4 | t1slo5 >>> 28)
+    const t2shi16 = (t1slo5 << 4 | t1shi5 >>> 28)
+    const t2slo7 = (t1slo10 << 3 | t1shi10 >>> 29)
+    const t2shi7 = (t1shi10 << 3 | t1slo10 >>> 29)
+    const t2slo23 = (t1shi15 << 9 | t1slo15 >>> 23)
+    const t2shi23 = (t1slo15 << 9 | t1shi15 >>> 23)
+    const t2slo14 = (t1slo20 << 18 | t1shi20 >>> 14)
+    const t2shi14 = (t1shi20 << 18 | t1slo20 >>> 14)
+    const t2slo10 = (t1slo1 << 1 | t1shi1 >>> 31)
+    const t2shi10 = (t1shi1 << 1 | t1slo1 >>> 31)
+    const t2slo1 = (t1shi6 << 12 | t1slo6 >>> 20)
+    const t2shi1 = (t1slo6 << 12 | t1shi6 >>> 20)
+    const t2slo17 = (t1slo11 << 10 | t1shi11 >>> 22)
+    const t2shi17 = (t1shi11 << 10 | t1slo11 >>> 22)
+    const t2slo8 = (t1shi16 << 13 | t1slo16 >>> 19)
+    const t2shi8 = (t1slo16 << 13 | t1shi16 >>> 19)
+    const t2slo24 = (t1slo21 << 2 | t1shi21 >>> 30)
+    const t2shi24 = (t1shi21 << 2 | t1slo21 >>> 30)
+    const t2slo20 = (t1shi2 << 30 | t1slo2 >>> 2)
+    const t2shi20 = (t1slo2 << 30 | t1shi2 >>> 2)
+    const t2slo11 = (t1slo7 << 6 | t1shi7 >>> 26)
+    const t2shi11 = (t1shi7 << 6 | t1slo7 >>> 26)
+    const t2slo2 = (t1shi12 << 11 | t1slo12 >>> 21)
+    const t2shi2 = (t1slo12 << 11 | t1shi12 >>> 21)
+    const t2slo18 = (t1slo17 << 15 | t1shi17 >>> 17)
+    const t2shi18 = (t1shi17 << 15 | t1slo17 >>> 17)
+    const t2slo9 = (t1shi22 << 29 | t1slo22 >>> 3)
+    const t2shi9 = (t1slo22 << 29 | t1shi22 >>> 3)
+    const t2slo5 = (t1slo3 << 28 | t1shi3 >>> 4)
+    const t2shi5 = (t1shi3 << 28 | t1slo3 >>> 4)
+    const t2slo21 = (t1shi8 << 23 | t1slo8 >>> 9)
+    const t2shi21 = (t1slo8 << 23 | t1shi8 >>> 9)
+    const t2slo12 = (t1slo13 << 25 | t1shi13 >>> 7)
+    const t2shi12 = (t1shi13 << 25 | t1slo13 >>> 7)
+    const t2slo3 = (t1slo18 << 21 | t1shi18 >>> 11)
+    const t2shi3 = (t1shi18 << 21 | t1slo18 >>> 11)
+    const t2slo19 = (t1shi23 << 24 | t1slo23 >>> 8)
+    const t2shi19 = (t1slo23 << 24 | t1shi23 >>> 8)
+    const t2slo15 = (t1slo4 << 27 | t1shi4 >>> 5)
+    const t2shi15 = (t1shi4 << 27 | t1slo4 >>> 5)
+    const t2slo6 = (t1slo9 << 20 | t1shi9 >>> 12)
+    const t2shi6 = (t1shi9 << 20 | t1slo9 >>> 12)
+    const t2slo22 = (t1shi14 << 7 | t1slo14 >>> 25)
+    const t2shi22 = (t1slo14 << 7 | t1shi14 >>> 25)
+    const t2slo13 = (t1slo19 << 8 | t1shi19 >>> 24)
+    const t2shi13 = (t1shi19 << 8 | t1slo19 >>> 24)
+    const t2slo4 = (t1slo24 << 14 | t1shi24 >>> 18)
+    const t2shi4 = (t1shi24 << 14 | t1slo24 >>> 18)
 
     // chi
     s[0] = t2slo0 ^ (~t2slo1 & t2slo2)
diff --git a/lib/keccak.js b/lib/keccak.js
index 3ce0818..64ecd94 100644
--- a/lib/keccak.js
+++ b/lib/keccak.js
@@ -1,6 +1,6 @@
 'use strict'
-var Buffer = require('safe-buffer').Buffer
-var keccakState = require('./keccak-state-unroll')
+const Buffer = require('safe-buffer').Buffer
+const keccakState = require('./keccak-state-unroll')
 
 function Keccak () {
   // much faster than `new Array(50)`
@@ -18,14 +18,14 @@ function Keccak () {
 }
 
 Keccak.prototype.initialize = function (rate, capacity) {
-  for (var i = 0; i < 50; ++i) this.state[i] = 0
+  for (let i = 0; i < 50; ++i) this.state[i] = 0
   this.blockSize = rate / 8
   this.count = 0
   this.squeezing = false
 }
 
 Keccak.prototype.absorb = function (data) {
-  for (var i = 0; i < data.length; ++i) {
+  for (let i = 0; i < data.length; ++i) {
     this.state[~~(this.count / 4)] ^= data[i] << (8 * (this.count % 4))
     this.count += 1
     if (this.count === this.blockSize) {
@@ -47,7 +47,7 @@ Keccak.prototype.absorbLastFewBits = function (bits) {
 Keccak.prototype.squeeze = function (length) {
   if (!this.squeezing) this.absorbLastFewBits(0x01)
 
-  var output = Buffer.alloc(length)
+  const output = Buffer.alloc(length)
   for (var i = 0; i < length; ++i) {
     output[i] = (this.state[~~(this.count / 4)] >>> (8 * (this.count % 4))) & 0xff
     this.count += 1
@@ -61,7 +61,7 @@ Keccak.prototype.squeeze = function (length) {
 }
 
 Keccak.prototype.copy = function (dest) {
-  for (var i = 0; i < 50; ++i) dest.state[i] = this.state[i]
+  for (let i = 0; i < 50; ++i) dest.state[i] = this.state[i]
   dest.blockSize = this.blockSize
   dest.count = this.count
   dest.squeezing = this.squeezing
diff --git a/package.json b/package.json
index dcf198f..9a656a5 100644
--- a/package.json
+++ b/package.json
@@ -38,20 +38,20 @@
     "unit": "tape test/index.js"
   },
   "dependencies": {
-    "bindings": "^1.2.1",
-    "inherits": "^2.0.3",
-    "nan": "^2.2.1",
-    "safe-buffer": "^5.1.0"
+    "bindings": "^1.5.0",
+    "inherits": "^2.0.4",
+    "nan": "^2.14.0",
+    "safe-buffer": "^5.2.0"
   },
   "devDependencies": {
-    "browserify": "^14.1.0",
-    "nyc": "^11.0.2",
-    "proxyquire": "^1.7.10",
-    "standard": "^10.0.2",
-    "tape": "^4.5.1"
+    "browserify": "^16.5.0",
+    "nyc": "^14.1.1",
+    "proxyquire": "^2.1.3",
+    "standard": "^14.3.1",
+    "tape": "^4.11.0"
   },
   "engines": {
-    "node": ">=6.0.0"
+    "node": ">=5.12.0"
   },
   "gypfile": true,
   "browser": {
diff --git a/test/js-keccak.js b/test/js-keccak.js
index 1351972..9a6bfcf 100644
--- a/test/js-keccak.js
+++ b/test/js-keccak.js
@@ -76,7 +76,7 @@ test('rol64lo', (t) => {
     [0b10000000000000000000000000000000, 0b00000000000000000000000000000000, 63, '0b01000000000000000000000000000000']
   ]
 
-  for (let fixture of fixtures) {
+  for (const fixture of fixtures) {
     t.equal(to32bin(keccakState._rol64lo(fixture[0], fixture[1], fixture[2])), fixture[3])
   }
 
@@ -94,7 +94,7 @@ test('rol64hi', (t) => {
     [0b00000000000000000000000000000000, 0b10000000000000000000000000000000, 63, '0b01000000000000000000000000000000']
   ]
 
-  for (let fixture of fixtures) {
+  for (const fixture of fixtures) {
     t.equal(to32bin(keccakState._rol64hi(fixture[0], fixture[1], fixture[2])), fixture[3])
   }
 
diff --git a/test/vectors-keccak.js b/test/vectors-keccak.js
index c17f1b3..442a4f4 100644
--- a/test/vectors-keccak.js
+++ b/test/vectors-keccak.js
@@ -15,7 +15,7 @@ module.exports = (name, createHash) => {
     const vector = vectors[i]
     const data = Buffer.from(vector.input, 'hex')
 
-    for (let hash of ['keccak224', 'keccak256', 'keccak384', 'keccak512']) {
+    for (const hash of ['keccak224', 'keccak256', 'keccak384', 'keccak512']) {
       test(`${name} ${hash} vector#${i}`, (t) => {
         t.equal(createHash(hash).update(data).digest('hex'), vector[hash])
         t.end()
diff --git a/util/keccak-state-unroll.js b/util/keccak-state-unroll.js
index c9441f7..26893b5 100644
--- a/util/keccak-state-unroll.js
+++ b/util/keccak-state-unroll.js
@@ -70,8 +70,8 @@ process.stdout.write(`
 `)
 
 for (let x = 0; x < 5; ++x) {
-  let next = (x + 1) % 5
-  let prev = (x + 4) % 5
+  const next = (x + 1) % 5
+  const prev = (x + 4) % 5
 
   process.stdout.write(`
     ${x === 0 ? 'var ' : ''}lo = lo${prev} ^ ${genROL64LO(`lo${next}`, `hi${next}`, 1)}`)