diff --git a/composer.json b/composer.json
index be91918..d3852c1 100644
--- a/composer.json
+++ b/composer.json
@@ -24,6 +24,7 @@
     },
     "require": {
         "web3p/rlp": "~0.2.1",
+        "web3p/ethereum-util": "~0.1",
         "kornrunner/keccak": "~1",
         "simplito/elliptic-php": "1.0.3"
     }
diff --git a/composer.lock b/composer.lock
index 36e995b..7582d6b 100644
--- a/composer.lock
+++ b/composer.lock
@@ -1,10 +1,10 @@
 {
     "_readme": [
         "This file locks the dependencies of your project to a known state",
-        "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
+        "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#composer-lock-the-lock-file",
         "This file is @generated automatically"
     ],
-    "content-hash": "58574e4ec1c8e466562f93cf7600d2c9",
+    "content-hash": "929d6e6b66956d43517b3e5f0c87692f",
     "packages": [
         {
             "name": "kornrunner/keccak",