diff --git a/internal/clis/hmpki/file_utils.go b/internal/clis/hmpki/file_utils.go
new file mode 100644
index 0000000..3a9641e
--- /dev/null
+++ b/internal/clis/hmpki/file_utils.go
@@ -0,0 +1,24 @@
+package hmpki
+
+import (
+	"os"
+)
+
+// CreateFileWith Creates a new file (fails it if already exists) with the
+// given content and permissions.
+func createFileWith(name string, content []byte, perms os.FileMode) error {
+	f, err := os.OpenFile(
+		name,
+		// Write only, and fail if it alreay exists.
+		os.O_WRONLY|os.O_CREATE|os.O_EXCL,
+		perms,
+	)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	if _, err = f.Write(content); err != nil {
+		return err
+	}
+	return nil
+}