diff --git a/crypto_box.js b/crypto_box.js
index 134c1b6..12a9e44 100644
--- a/crypto_box.js
+++ b/crypto_box.js
@@ -1,3 +1,6 @@
+const { crypto_hash_sha512 } = require('./crypto_hash')
+const { memzero } = require('./')
+
 module.exports = {
   crypto_box_keypair,
   crypto_box_seal,
@@ -19,6 +22,19 @@ function crypto_box_keypair(pk, sk) {
   return crypto_scalarmult_base(pk, sk)
 }
 
+function crypto_box_seed_keypair(pk, sk, seed) {
+  check(pk, crypto_box_PUBLICKEYBYTES)
+  check(sk, crypto_box_SECRETKEYBYTES)
+  check(sk, crypto_box_SEEDBYTES)
+
+  const hash = Buffer.alloc(64)
+  crypto_hash_sha512(hash, seed, 32)
+  sk.set(hash, 0, 0, 32)
+  memzero(hash)
+
+  return crypto_scalarmult_base(pk, sk)
+}
+
 function crypto_box_seal(c, m, pk) {
   check(c, crypto_box_SEALBYTES + m.length)
   check(pk, crypto_box_PUBLICKEYBYTES)
diff --git a/crypto_kx.js b/crypto_kx.js
new file mode 100644
index 0000000..04fb0bb
--- /dev/null
+++ b/crypto_kx.js
@@ -0,0 +1,9 @@
+const { crypto_box_keypair, crypto_box_seed_keypair } = require('./crypto_box')
+
+function crypto_kx_keypair (pk, sk) {
+  return crypto_box_keypair(pk, sk)
+}
+
+function crypto_kx_seed_keypair (pk, sk, seed) {
+  return crypto_box_seed_keypair(pk, sk, seed)
+}