diff --git a/util/common/random.go b/util/common/random.go
new file mode 100644
index 00000000..ccd35e91
--- /dev/null
+++ b/util/common/random.go
@@ -0,0 +1,18 @@
+package common
+
+import (
+	"crypto/rand"
+	"math/big"
+)
+
+// RandomInt 返回一个 0 .. max-1 之间的随机整数（使用 crypto/rand）
+func RandomInt(max int) int {
+	if max <= 0 {
+		return 0
+	}
+	n, err := rand.Int(rand.Reader, big.NewInt(int64(max)))
+	if err != nil {
+		return 0
+	}
+	return int(n.Int64())
+}