diff --git a/src/util/digest.cpp b/src/util/digest.cpp
index 55eb459..8053fdb 100644
--- a/src/util/digest.cpp
+++ b/src/util/digest.cpp
@@ -29,6 +29,8 @@
 namespace ndn {
 namespace util {
 
+const size_t Sha256::DIGEST_SIZE;
+
 Sha256::Sha256()
 {
   reset();
@@ -130,6 +132,14 @@
   return toHex(*buf);
 }
 
+ConstBufferPtr
+Sha256::computeDigest(const uint8_t* buffer, size_t size)
+{
+  Sha256 sha256;
+  sha256.update(buffer, size);
+  return sha256.computeDigest();
+}
+
 std::ostream&
 operator<<(std::ostream& os, Sha256& digest)
 {