diff --git a/package-lock.json b/package-lock.json
index e47c442..933ef39 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -152,6 +152,11 @@
       "integrity": "sha1-muuabF6IY4qtFx4Wf1kAq+JINdA=",
       "dev": true
     },
+    "bluebird": {
+      "version": "3.5.1",
+      "resolved": "https://registry.npmjs.org/bluebird/-/bluebird-3.5.1.tgz",
+      "integrity": "sha512-MKiLiV+I1AA596t9w1sQJ8jkiSr5+ZKi0WKrYGUn6d1Fx+Ij4tIj+m2WMQSGczs5jZVxV339chE8iwk6F64wjA=="
+    },
     "bn.js": {
       "version": "4.11.8",
       "resolved": "https://registry.npmjs.org/bn.js/-/bn.js-4.11.8.tgz",
@@ -387,6 +392,11 @@
         "elliptic": "6.4.0"
       }
     },
+    "create-error": {
+      "version": "0.3.1",
+      "resolved": "https://registry.npmjs.org/create-error/-/create-error-0.3.1.tgz",
+      "integrity": "sha1-aYECRaYp5lRDK/BDdzYAA6U1GiM="
+    },
     "create-hash": {
       "version": "1.1.3",
       "resolved": "https://registry.npmjs.org/create-hash/-/create-hash-1.1.3.tgz",
@@ -2406,6 +2416,15 @@
       "integrity": "sha1-nsYfeQSYdXB9aUFFlv2Qek1xHnM=",
       "dev": true
     },
+    "random-number-csprng": {
+      "version": "1.0.2",
+      "resolved": "https://registry.npmjs.org/random-number-csprng/-/random-number-csprng-1.0.2.tgz",
+      "integrity": "sha1-/NEg5i3/wsB2dMfD/gHhayX3OiY=",
+      "requires": {
+        "bluebird": "3.5.1",
+        "create-error": "0.3.1"
+      }
+    },
     "randomatic": {
       "version": "1.1.7",
       "resolved": "https://registry.npmjs.org/randomatic/-/randomatic-1.1.7.tgz",
diff --git a/package.json b/package.json
index 7d87b26..4651797 100644
--- a/package.json
+++ b/package.json
@@ -22,5 +22,9 @@
   "homepage": "https://github.com/dmuth/diceware#readme",
   "devDependencies": {
     "webpack": "^3.8.1"
+  },
+  "dependencies": {
+    "bluebird": "^3.5.1",
+    "random-number-csprng": "^1.0.2"
   }
 }