diff --git a/merkle/iavl_test.go b/merkle/iavl_test.go
index a6d51c0d..b009e55e 100644
--- a/merkle/iavl_test.go
+++ b/merkle/iavl_test.go
@@ -154,7 +154,7 @@ func TestIntegration(t *testing.T) {
     var updated bool
 
     randomRecord := func() *record {
-        return &record{ RandStr(20), RandStr(20) }
+        return &record{ randstr(20), randstr(20) }
     }
 
     for i := range records {
@@ -179,7 +179,7 @@ func TestIntegration(t *testing.T) {
         if has := tree.Has(r.key); !has {
             t.Error("Missing key", r.key)
         }
-        if has := tree.Has(RandStr(12)); has {
+        if has := tree.Has(randstr(12)); has {
             t.Error("Table has extra key")
         }
         if val := tree.Get(r.key); !(val.(String)).Equals(r.value) {
@@ -197,7 +197,7 @@ func TestIntegration(t *testing.T) {
             if has := tree.Has(r.key); !has {
                 t.Error("Missing key", r.key)
             }
-            if has := tree.Has(RandStr(12)); has {
+            if has := tree.Has(randstr(12)); has {
                 t.Error("Table has extra key")
             }
             if val := tree.Get(r.key); !(val.(String)).Equals(r.value) {
@@ -216,7 +216,7 @@ func TestPersistence(t *testing.T) {
     // Create some random key value pairs
     records := make(map[String]String)
     for i:=0; i<10000; i++ {
-        records[String(RandStr(20))] = String(RandStr(20))
+        records[String(randstr(20))] = String(randstr(20))
     }
 
     // Construct some tree and save it
@@ -241,7 +241,7 @@ func TestPersistence(t *testing.T) {
 func BenchmarkHash(b *testing.B) {
     b.StopTimer()
 
-    s := RandStr(128)
+    s := randstr(128)
 
     b.StartTimer()
     for i := 0; i < b.N; i++ {
@@ -260,7 +260,7 @@ func BenchmarkImmutableAvlTree(b *testing.B) {
     }
 
     randomRecord := func() *record {
-        return &record{ RandStr(32), RandStr(32) }
+        return &record{ randstr(32), randstr(32) }
     }
 
     t := NewIAVLTree(nil)
@@ -269,6 +269,8 @@ func BenchmarkImmutableAvlTree(b *testing.B) {
         t.Put(r.key, r.value)
     }
 
+    fmt.Println("ok, starting")
+
     b.StartTimer()
     for i := 0; i < b.N; i++ {
         r := randomRecord()
diff --git a/merkle/util.go b/merkle/util.go
index 95badde0..f2183d91 100644
--- a/merkle/util.go
+++ b/merkle/util.go
@@ -1,8 +1,7 @@
 package merkle
 
 import (
-    "math/big"
-    "crypto/rand"
+    "os"
     "fmt"
 )
 
@@ -32,17 +31,18 @@ func printIAVLNode(node *IAVLNode, indent int) {
 
 }
 
-const allRandChars = "0123456789"
-
-func RandStr(numChars int) String {
-    var res string
-    for i:=0; i<numChars; i++ {
-        v, err := rand.Int(rand.Reader, big.NewInt(int64(10)))
-        if err != nil { panic(err) }
-        randIndex := int(v.Int64())
-        res = res + allRandChars[randIndex:randIndex+1]
+func randstr(length int) String {
+    if urandom, err := os.Open("/dev/urandom"); err != nil {
+        panic(err)
+    } else {
+        slice := make([]byte, length)
+        if _, err := urandom.Read(slice); err != nil {
+            panic(err)
+        }
+        urandom.Close()
+        return String(slice)
     }
-    return String(res)
+    panic("unreachable")
 }
 
 func maxUint8(a, b uint8) uint8 {