diff --git a/contrib/keygen-html/Makefile b/contrib/keygen-html/Makefile
new file mode 100644
index 0000000..a3acec0
--- /dev/null
+++ b/contrib/keygen-html/Makefile
@@ -0,0 +1,6 @@
+curve25519_generate.js: src/curve25519_generate.c src/glue.js
+	emcc -O2 --memory-init-file 0 --closure 1 --post-js src/glue.js -s 'EXTRA_EXPORTED_RUNTIME_METHODS=["Pointer_stringify"]' -o $@ src/curve25519_generate.c
+clean:
+	rm -f curve25519_generate.js
+all: curve25519_generate.js
+.PHONY: clean all
diff --git a/contrib/keygen-html/keygen.html b/contrib/keygen-html/keygen.html
index 694e1ff..45efec7 100644
--- a/contrib/keygen-html/keygen.html
+++ b/contrib/keygen-html/keygen.html
@@ -1,4 +1,4 @@
-<script src="wireguard.js"></script>
+<script src="curve25519_generate.js" onError='document.write("<h3>Did you forget to run \"make\" to compile curve25519_generate.js?</h3><!--");'></script>
 <script>
 /* SPDX-License-Identifier: GPL-2.0
  *
diff --git a/contrib/keygen-html/src/curve25519_generate.c b/contrib/keygen-html/src/curve25519_generate.c
new file mode 100644
index 0000000..fc47575
--- /dev/null
+++ b/contrib/keygen-html/src/curve25519_generate.c
@@ -0,0 +1,97 @@
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * Copyright (C) 2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ */
+
+#include <emscripten.h>
+
+typedef unsigned long long  u64;
+typedef unsigned int u32;
+typedef unsigned char u8;
+typedef u32 __le32;
+
+enum { CURVE25519_POINT_SIZE = 32 };
+
+#ifndef __always_inline
+#define __always_inline __inline __attribute__((__always_inline__))
+#endif
+#ifndef noinline
+#define noinline __attribute__((noinline))
+#endif
+#ifndef __aligned
+#define __aligned(x) __attribute__((aligned(x)))
+#endif
+#ifndef __force
+#define __force
+#endif
+
+#if __BYTE_ORDER == __LITTLE_ENDIAN
+#define le32_to_cpup(a) (*(a))
+#else
+#define le32_to_cpup(a) __builtin_bswap32(*(a))
+#endif
+
+#define memset(a, b, c) __builtin_memset(a, b, c)
+#define memcpy(a, b, c) __builtin_memcpy(a, b, c)
+#define memmove(a, b, c) __builtin_memmove(a, b, c)
+/* We don't even attempt to deal with this in javascript. */
+#define memzero_explicit(a, b)
+
+static __always_inline void normalize_secret(u8 secret[CURVE25519_POINT_SIZE])
+{
+	secret[0] &= 248;
+	secret[31] &= 127;
+	secret[31] |= 64;
+}
+
+#include "../../../../src/crypto/curve25519-fiat32.h"
+
+EMSCRIPTEN_KEEPALIVE void curve25519_generate_public(u8 public[static 32], const u8 private[static 32])
+{
+	static const u8 basepoint[32] = { 9 };
+
+	curve25519_generic(public, private, basepoint);
+}
+
+EMSCRIPTEN_KEEPALIVE void curve25519_generate_private(u8 private[static 32])
+{
+	int i;
+
+	EM_ASM({
+		/* Same trick as libsodium */
+		var getRandomValue = function() {
+			var buf = new Uint32Array(1);
+			window.crypto.getRandomValues(buf);
+			return buf[0] >>> 0;
+		};
+		Module.getRandomValue = getRandomValue;
+	});
+	
+	for (i = 0; i < 32; ++i)
+		private[i] = EM_ASM_INT_V({ return Module.getRandomValue(); });
+	normalize_secret(private);
+}
+
+static inline void encode_base64(char dest[4], const u8 src[3])
+{
+	const u8 input[] = { (src[0] >> 2) & 63, ((src[0] << 4) | (src[1] >> 4)) & 63, ((src[1] << 2) | (src[2] >> 6)) & 63, src[2] & 63 };
+
+	for (unsigned int i = 0; i < 4; ++i)
+		dest[i] = input[i] + 'A'
+			  + (((25 - input[i]) >> 8) & 6)
+			  - (((51 - input[i]) >> 8) & 75)
+			  - (((61 - input[i]) >> 8) & 15)
+			  + (((62 - input[i]) >> 8) & 3);
+
+}
+
+EMSCRIPTEN_KEEPALIVE void key_to_base64(char base64[static 45], const u8 key[static 32])
+{
+	unsigned int i;
+
+	for (i = 0; i < 32 / 3; ++i)
+		encode_base64(&base64[i * 4], &key[i * 3]);
+	encode_base64(&base64[i * 4], (const u8[]){ key[i * 3 + 0], key[i * 3 + 1], 0 });
+	base64[45 - 2] = '=';
+	base64[45 - 1] = '\0';
+}
diff --git a/contrib/keygen-html/src/glue.js b/contrib/keygen-html/src/glue.js
new file mode 100644
index 0000000..981e533
--- /dev/null
+++ b/contrib/keygen-html/src/glue.js
@@ -0,0 +1,25 @@
+/*! SPDX-License-Identifier: GPL-2.0
+ *
+ * Copyright (C) 2015-2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ */
+window["WireGuard"] = {
+	"generateKeypair": function() {
+		var privateKey = Module["_malloc"](32);
+		var publicKey = Module["_malloc"](32);
+		Module["_curve25519_generate_private"](privateKey);
+		Module["_curve25519_generate_public"](publicKey, privateKey);
+		var privateBase64 = Module["_malloc"](45);
+		var publicBase64 = Module["_malloc"](45);
+		Module["_key_to_base64"](privateBase64, privateKey);
+		Module["_key_to_base64"](publicBase64, publicKey);
+		Module["_free"](privateKey);
+		Module["_free"](publicKey);
+		var keypair = {
+			publicKey: Module["Pointer_stringify"](publicBase64),
+			privateKey: Module["Pointer_stringify"](privateBase64)
+		};
+		Module["_free"](privateBase64);
+		Module["_free"](publicBase64);
+		return keypair;
+	}
+};
diff --git a/contrib/keygen-html/wireguard.js b/contrib/keygen-html/wireguard.js
deleted file mode 100644
index b77dec8..0000000
--- a/contrib/keygen-html/wireguard.js
+++ /dev/null
@@ -1,186 +0,0 @@
-/*! SPDX-License-Identifier: GPL-2.0
- *
- * Copyright (C) 2015-2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
- */
-
-(function() {
-	function gf(init) {
-		var r = new Float64Array(16);
-		if (init) {
-			for (var i = 0; i < init.length; ++i)
-				r[i] = init[i];
-		}
-		return r;
-	}
-
-	function pack(o, n) {
-		var b, m = gf(), t = gf();
-		for (var i = 0; i < 16; ++i)
-			t[i] = n[i];
-		carry(t);
-		carry(t);
-		carry(t);
-		for (var j = 0; j < 2; ++j) {
-			m[0] = t[0] - 0xffed;
-			for (var i = 1; i < 15; ++i) {
-				m[i] = t[i] - 0xffff - ((m[i - 1] >> 16) & 1);
-				m[i - 1] &= 0xffff;
-			}
-			m[15] = t[15] - 0x7fff - ((m[14] >> 16) & 1);
-			b = (m[15] >> 16) & 1;
-			m[14] &= 0xffff;
-			cswap(t, m, 1 - b);
-		}
-		for (var i = 0; i < 16; ++i) {
-			o[2 * i] = t[i] & 0xff;
-			o[2 * i + 1] = t[i] >> 8;
-		}
-	}
-
-	function carry(o) {
-		var c;
-		for (var i = 0; i < 16; ++i) {
-			o[i] += 65536;
-			c = Math.floor(o[i] / 65536);
-			o[(i + 1) * (i < 15 ? 1 : 0)] += c - 1 + 37 * (c - 1) * (i === 15 ? 1 : 0);
-			o[i] -= (c * 65536);
-		}
-	}
-
-	function cswap(p, q, b) {
-		var t, c = ~(b - 1);
-		for (var i = 0; i < 16; ++i) {
-			t = c & (p[i] ^ q[i]);
-			p[i] ^= t;
-			q[i] ^= t;
-		}
-	}
-
-	function add(o, a, b) {
-		for (var i = 0; i < 16; ++i)
-			o[i] = (a[i] + b[i]) | 0;
-	}
-
-	function subtract(o, a, b) {
-		for (var i = 0; i < 16; ++i)
-			o[i] = (a[i] - b[i]) | 0;
-	}
-
-	function multmod(o, a, b) {
-		var t = new Float64Array(31);
-		for (var i = 0; i < 16; ++i) {
-			for (var j = 0; j < 16; ++j)
-				t[i + j] += a[i] * b[j];
-		}
-		for (var i = 0; i < 15; ++i)
-			t[i] += 38 * t[i + 16];
-		for (var i = 0; i < 16; ++i)
-			o[i] = t[i];
-		carry(o);
-		carry(o);
-	}
-
-	function invert(o, i) {
-		var c = gf();
-		for (var a = 0; a < 16; ++a)
-			c[a] = i[a];
-		for (var a = 253; a >= 0; --a) {
-			multmod(c, c, c);
-			if (a !== 2 && a !== 4)
-				multmod(c, c, i);
-		}
-		for (var a = 0; a < 16; ++a)
-			o[a] = c[a];
-	}
-
-	function normalizeKey(z) {
-		z[31] = (z[31] & 127) | 64;
-		z[0] &= 248;
-	}
-
-	function generatePublicKey(privateKey) {
-		var r, z = new Uint8Array(32);
-		var a = gf([1]),
-			b = gf([9]),
-			c = gf(),
-			d = gf([1]),
-			e = gf(),
-			f = gf(),
-			_121665 = gf([0xdb41, 1]),
-			_9 = gf([9]);
-		for (var i = 0; i < 32; ++i)
-			z[i] = privateKey[i];
-		normalizeKey(z);
-		for (var i = 254; i >= 0; --i) {
-			r = (z[i >>> 3] >>> (i & 7)) & 1;
-			cswap(a, b, r);
-			cswap(c, d, r);
-			add(e, a, c);
-			subtract(a, a, c);
-			add(c, b, d);
-			subtract(b, b, d);
-			multmod(d, e, e);
-			multmod(f, a, a);
-			multmod(a, c, a);
-			multmod(c, b, e);
-			add(e, a, c);
-			subtract(a, a, c);
-			multmod(b, a, a);
-			subtract(c, d, f);
-			multmod(a, c, _121665);
-			add(a, a, d);
-			multmod(c, c, a);
-			multmod(a, d, f);
-			multmod(d, b, _9);
-			multmod(b, e, e);
-			cswap(a, b, r);
-			cswap(c, d, r);
-		}
-		invert(c, c);
-		multmod(a, a, c);
-		pack(z, a);
-		return z;
-	}
-
-	function generatePresharedKey() {
-		var privateKey = new Uint8Array(32);
-		window.crypto.getRandomValues(privateKey);
-		return privateKey;
-	}
-
-	function generatePrivateKey() {
-		var privateKey = generatePresharedKey();
-		normalizeKey(privateKey);
-		return privateKey;
-	}
-
-	function encodeBase64(dest, src) {
-		var input = Uint8Array.from([(src[0] >> 2) & 63, ((src[0] << 4) | (src[1] >> 4)) & 63, ((src[1] << 2) | (src[2] >> 6)) & 63, src[2] & 63]);
-		for (var i = 0; i < 4; ++i)
-			dest[i] = input[i] + 65 +
-			(((25 - input[i]) >> 8) & 6) -
-			(((51 - input[i]) >> 8) & 75) -
-			(((61 - input[i]) >> 8) & 15) +
-			(((62 - input[i]) >> 8) & 3);
-	}
-
-	function keyToBase64(key) {
-		var i, base64 = new Uint8Array(44);
-		for (i = 0; i < 32 / 3; ++i)
-			encodeBase64(base64.subarray(i * 4), key.subarray(i * 3));
-		encodeBase64(base64.subarray(i * 4), Uint8Array.from([key[i * 3 + 0], key[i * 3 + 1], 0]));
-		base64[43] = 61;
-		return String.fromCharCode.apply(null, base64);
-	}
-
-	window["WireGuard"] = {
-		"generateKeypair": function() {
-			var privateKey = generatePrivateKey();
-			var publicKey = generatePublicKey(privateKey);
-			return {
-				publicKey: keyToBase64(publicKey),
-				privateKey: keyToBase64(privateKey)
-			};
-		}
-	};
-})();