diff --git a/package.json b/package.json
index 645288a..dfd3588 100644
--- a/package.json
+++ b/package.json
@@ -39,8 +39,7 @@
     "benchmark": "node -r ./.babel-register test/benchmarks"
   },
   "dependencies": {
-    "@chainsafe/bls-keygen": "^0.2.0",
-    "assert": "^1.4.1",
+    "@chainsafe/bls-keygen": "^0.3.0",
     "bls-eth-wasm": "^0.4.1"
   },
   "devDependencies": {
diff --git a/src/helpers/index.ts b/src/helpers/index.ts
new file mode 100644
index 0000000..178cd64
--- /dev/null
+++ b/src/helpers/index.ts
@@ -0,0 +1 @@
+export * from "./utils";
diff --git a/src/helpers/utils.ts b/src/helpers/utils.ts
index 7430d7d..b81b6ae 100644
--- a/src/helpers/utils.ts
+++ b/src/helpers/utils.ts
@@ -1,17 +1,9 @@
-import assert from "assert";
 import {PUBLIC_KEY_LENGTH, SIGNATURE_LENGTH} from "../constants";
 
-/**
- * Pads byte array with zeroes on left side up to desired length.
- * Throws if source is larger than desired result.
- * @param source
- * @param length
- */
-export function padLeft(source: Uint8Array, length: number): Buffer {
-  assert(source.length <= length, "Given array must be smaller or equal to desired array size");
-  const result = Buffer.alloc(length, 0);
-  result.set(source, length - source.length);
-  return result;
+export function assert(condition: unknown, message = "Assertion failed"): asserts condition {
+  if (!condition) {
+    throw new Error(message);
+  }
 }
 
 export const EMPTY_PUBLIC_KEY = Buffer.alloc(PUBLIC_KEY_LENGTH);
diff --git a/src/index.ts b/src/index.ts
index b398620..6dfc0ac 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -3,7 +3,7 @@ import {PrivateKey} from "./privateKey";
 import {PublicKey} from "./publicKey";
 import {Signature} from "./signature";
 import {PUBLIC_KEY_LENGTH} from "./constants";
-import assert from "assert";
+import {assert} from "./helpers";
 
 export {Keypair, PrivateKey, PublicKey, Signature};
 
diff --git a/src/privateKey.ts b/src/privateKey.ts
index dbf3160..24cc845 100644
--- a/src/privateKey.ts
+++ b/src/privateKey.ts
@@ -1,5 +1,5 @@
 import {SECRET_KEY_LENGTH} from "./constants";
-import assert from "assert";
+import {assert} from "./helpers";
 import {SecretKeyType} from "bls-eth-wasm";
 import {generateRandomSecretKey} from "@chainsafe/bls-keygen";
 import {getContext} from "./context";
diff --git a/src/publicKey.ts b/src/publicKey.ts
index c7537c7..9f23851 100644
--- a/src/publicKey.ts
+++ b/src/publicKey.ts
@@ -2,7 +2,7 @@ import {PrivateKey} from "./privateKey";
 import {PublicKeyType} from "bls-eth-wasm";
 import {getContext} from "./context";
 import {PUBLIC_KEY_LENGTH} from "./constants";
-import assert from "assert";
+import {assert} from "./helpers";
 import {Signature} from "./signature";
 import {EMPTY_PUBLIC_KEY} from "./helpers/utils";
 
diff --git a/src/signature.ts b/src/signature.ts
index 5da9104..74d6ed0 100644
--- a/src/signature.ts
+++ b/src/signature.ts
@@ -1,4 +1,4 @@
-import assert from "assert";
+import {assert} from "./helpers";
 import {FP_POINT_LENGTH} from "./constants";
 import {SignatureType} from "bls-eth-wasm";
 import {getContext} from "./context";
diff --git a/yarn.lock b/yarn.lock
index 4699931..48d79da 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -799,26 +799,25 @@
     "@assemblyscript/loader" "^0.9.2"
     buffer "^5.4.3"
 
-"@chainsafe/bls-hd-key@^0.1.0":
-  version "0.1.0"
-  resolved "https://registry.yarnpkg.com/@chainsafe/bls-hd-key/-/bls-hd-key-0.1.0.tgz#5e51de16801f4b4b421e418f0d1ef0692df0c585"
-  integrity sha512-VZj+Ml4YTPz+d/K2n9q/9bLlIJnTr/xdAC5w1eCvIFtcQrZCY1Zw+bCcXKX1q6sbZpO9xhyuoepJzJX9VkMPqw==
+"@chainsafe/bls-hd-key@^0.2.0":
+  version "0.2.0"
+  resolved "https://registry.yarnpkg.com/@chainsafe/bls-hd-key/-/bls-hd-key-0.2.0.tgz#90aaf030150de64099e1fb27582b27bbe5ce5309"
+  integrity sha512-ps10jd99UWcm1qPo4spD/6hxFor9fsDgB0s2wJuFKqPdM2R+4LCowhv5kdGgGs3VIN1H8l+CgO08yC7X0WlBDQ==
   dependencies:
     assert "^2.0.0"
     bcrypto "^5.0.4"
     bn.js "^5.1.1"
     buffer "^5.4.3"
 
-"@chainsafe/bls-keygen@^0.2.0":
-  version "0.2.0"
-  resolved "https://registry.yarnpkg.com/@chainsafe/bls-keygen/-/bls-keygen-0.2.0.tgz#2089da875caff4334723c5ee45495e366dc57a2e"
-  integrity sha512-IcgOJ1UTiHX3T1FnSqTdf4gtavjpINPtmAwLZFQUxSuLPOfmxPPVN/yhAIYw5xCh9/mWkaFQ/dFUk6ys+BkfGQ==
+"@chainsafe/bls-keygen@^0.3.0":
+  version "0.3.0"
+  resolved "https://registry.yarnpkg.com/@chainsafe/bls-keygen/-/bls-keygen-0.3.0.tgz#d7472a945f6f49b5cb357241bfba2f5c12a635c5"
+  integrity sha512-5Iq6E5E987hyio74G1fXPYI3t9iVeHxRX1tDMpnCV9T82rPz061yFsMz3W3aXE26+k6+fcz0bsYX3ijOizkx+A==
   dependencies:
-    "@chainsafe/bls-hd-key" "^0.1.0"
-    assert "^2.0.0"
-    bcrypto "^5.0.4"
+    "@chainsafe/bls-hd-key" "^0.2.0"
     bip39 "^3.0.2"
     buffer "^5.4.3"
+    randombytes "^2.1.0"
 
 "@chainsafe/eth2-spec-tests@0.12.0":
   version "0.12.0"
@@ -1323,7 +1322,7 @@ asn1.js@^4.0.0:
     inherits "^2.0.1"
     minimalistic-assert "^1.0.0"
 
-assert@^1.1.1, assert@^1.4.1:
+assert@^1.1.1:
   version "1.5.0"
   resolved "https://registry.yarnpkg.com/assert/-/assert-1.5.0.tgz#55c109aaf6e0aefdb3dc4b71240c70bf574b18eb"
   integrity sha512-EDsgawzwoun2CZkCgtxJbv392v4nbk9XDD06zI+kQYoBM/3RBWLlEyJARDOmhAAosBjWACEkKL6S+lIZtcAubA==