diff --git a/ndn-cxx/security/transform/buffer-source.cpp b/ndn-cxx/security/transform/buffer-source.cpp
index 36f5d2d..515964f 100644
--- a/ndn-cxx/security/transform/buffer-source.cpp
+++ b/ndn-cxx/security/transform/buffer-source.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2020 Regents of the University of California.
+ * Copyright (c) 2013-2021 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -25,8 +25,13 @@
 namespace security {
 namespace transform {
 
+BufferSource::BufferSource(span<const uint8_t> buffer)
+  : m_bufs({buffer})
+{
+}
+
 BufferSource::BufferSource(const uint8_t* buf, size_t size)
-  : m_bufs({{buf, size}})
+  : BufferSource(make_span(buf, size))
 {
 }
 
@@ -35,11 +40,6 @@
 {
 }
 
-BufferSource::BufferSource(const Buffer& buffer)
-  : m_bufs({{buffer.data(), buffer.size()}})
-{
-}
-
 BufferSource::BufferSource(InputBuffers buffers)
   : m_bufs(std::move(buffers))
 {
@@ -50,14 +50,10 @@
 {
   BOOST_ASSERT(m_next != nullptr);
 
-  for (const auto& buffer : m_bufs) {
-    const uint8_t* buf = buffer.first;
-    size_t size = buffer.second;
-
-    while (size > 0) {
-      size_t nBytesWritten = m_next->write(buf, size);
-      buf += nBytesWritten;
-      size -= nBytesWritten;
+  for (auto buffer : m_bufs) {
+    while (!buffer.empty()) {
+      size_t nBytesWritten = m_next->write(buffer);
+      buffer = buffer.last(buffer.size() - nBytesWritten);
     }
   }