diff --git a/src/bn128.js b/src/bn128.js
index b9097df..8977e8b 100644
--- a/src/bn128.js
+++ b/src/bn128.js
@@ -18,7 +18,6 @@
 */
 
 const bigInt = require("./bigint.js");
-const assert = require("assert");
 
 const F1Field = require("./zqfield.js");
 const F2Field = require("./f2field.js");
@@ -160,9 +159,15 @@ class BN128 {
         }
 
         const Q1 = this.G2.affine(this._g2MulByQ(Qcopy));
-        assert(this.F2.equals(Q1[2], this.F2.one));
+        if (!this.F2.equals(Q1[2], this.F2.one))
+        {
+            throw new Error("Expected values are not equal");
+        }
         const Q2 = this.G2.affine(this._g2MulByQ(Q1));
-        assert(this.F2.equals(Q2[2], this.F2.one));
+        if (!this.F2.equals(Q2[2], this.F2.one))
+        {
+            throw new Error("Expected values are not equal");
+        }
 
         if (this.loopCountNef)
         {
diff --git a/src/polfield.js b/src/polfield.js
index 8ade7b1..1d9046c 100644
--- a/src/polfield.js
+++ b/src/polfield.js
@@ -25,7 +25,6 @@
  */
 
 const bigInt = require("./bigint.js");
-const assert = require("assert");
 
 class PolField {
     constructor (F) {
@@ -446,8 +445,12 @@ class PolField {
         let res = this.F.one;
         let r = i;
 
-        assert(i<n);
-        assert(1<<nbits === n);
+        if(i>=n) {
+            throw new Error("Given 'i' should be lower than 'n'");
+        }
+        else if (1<<nbits !== n) {
+            throw new Error(`Internal errlr: ${n} should equal ${1<<nbits}`);
+        }
 
         while (r>0) {
             if (r & 1 == 1) {
diff --git a/src/zqfield.js b/src/zqfield.js
index eb6488b..02846eb 100644
--- a/src/zqfield.js
+++ b/src/zqfield.js
@@ -17,11 +17,25 @@
     snarkjs. If not, see <https://www.gnu.org/licenses/>.
 */
 
-const crypto = require("crypto");
-
 const bigInt = require("./bigint");
 const fUtils = require("./futils.js");
 
+function getRandomByte() {
+    if (typeof window !== "undefined") { // Browser
+        if (typeof window.crypto !== "undefined") { // Supported
+            let array = new Uint8Array(1);
+            window.crypto.getRandomValues(array);
+            return array[0];
+        }
+        else { // fallback
+            return Math.floor(Math.random() * 256);
+        }
+    }
+    else { // NodeJS
+        return module.require("crypto").randomBytes(1)[0];
+    }
+}
+
 class ZqField {
     constructor(q) {
         this.q = bigInt(q);
@@ -85,7 +99,7 @@ class ZqField {
         let res = bigInt(0);
         let n = bigInt(this.q);
         while (!n.isZero()) {
-            res = res.shl(8).add(bigInt(crypto.randomBytes(1)[0]));
+            res = res.shl(8).add(bigInt(getRandomByte()));
             n = n.shr(8);
         }
         return res;