diff --git a/ndn-cpp/util/blob.hpp b/ndn-cpp/util/blob.hpp
index d71808d..ef13433 100644
--- a/ndn-cpp/util/blob.hpp
+++ b/ndn-cpp/util/blob.hpp
@@ -35,7 +35,7 @@
    * @param value A pointer to the byte array which is copied.
    * @param valueLength The length of value.
    */
-  Blob(const uint8_t* value, unsigned int valueLength)
+  Blob(const uint8_t* value, size_t valueLength)
   : ptr_lib::shared_ptr<const std::vector<uint8_t> >(new std::vector<uint8_t>(value, value + valueLength))
   {
   }
@@ -68,7 +68,7 @@
   /**
    * Return the length of the immutable byte array.
    */
-  unsigned int 
+  size_t 
   size() const
   {
     if (*this)
diff --git a/ndn-cpp/util/changed-event.cpp b/ndn-cpp/util/changed-event.cpp
index 1d12c75..63b4569 100644
--- a/ndn-cpp/util/changed-event.cpp
+++ b/ndn-cpp/util/changed-event.cpp
@@ -13,7 +13,7 @@
 void 
 ChangedEvent::fire()
 {
-  for (unsigned int i = 0; i < listeners_.size(); ++i)
+  for (size_t i = 0; i < listeners_.size(); ++i)
     listeners_[i]();
 }
 
diff --git a/ndn-cpp/util/dynamic-uint8-vector.cpp b/ndn-cpp/util/dynamic-uint8-vector.cpp
index 240baa6..ae1b621 100644
--- a/ndn-cpp/util/dynamic-uint8-vector.cpp
+++ b/ndn-cpp/util/dynamic-uint8-vector.cpp
@@ -10,14 +10,14 @@
 
 namespace ndn {
 
-DynamicUInt8Vector::DynamicUInt8Vector(unsigned int initialLength)
+DynamicUInt8Vector::DynamicUInt8Vector(size_t initialLength)
 : vector_(new vector<uint8_t>(initialLength))
 {
   ndn_DynamicUInt8Array_initialize(this, &vector_->front(), initialLength, DynamicUInt8Vector::realloc);
 }
 
 uint8_t*
-DynamicUInt8Vector::realloc(struct ndn_DynamicUInt8Array *self, uint8_t *array, unsigned int length)
+DynamicUInt8Vector::realloc(struct ndn_DynamicUInt8Array *self, uint8_t *array, size_t length)
 {
   // Because this method is private, assume there is not a problem with upcasting.
   DynamicUInt8Vector *thisObject = (DynamicUInt8Vector *)self;
diff --git a/ndn-cpp/util/dynamic-uint8-vector.hpp b/ndn-cpp/util/dynamic-uint8-vector.hpp
index 2c6247e..9550899 100644
--- a/ndn-cpp/util/dynamic-uint8-vector.hpp
+++ b/ndn-cpp/util/dynamic-uint8-vector.hpp
@@ -23,7 +23,7 @@
    * Create a new DynamicUInt8Vector with an initial length.
    * @param initialLength The initial size of the allocated vector.
    */
-  DynamicUInt8Vector(unsigned int initialLength);
+  DynamicUInt8Vector(size_t initialLength);
   
   /**
    * Get the shared_ptr to the allocated vector.
@@ -41,7 +41,7 @@
    * @return The front of the allocated vector.
    */
   static uint8_t*
-  realloc(struct ndn_DynamicUInt8Array *self, uint8_t *array, unsigned int length);
+  realloc(struct ndn_DynamicUInt8Array *self, uint8_t *array, size_t length);
   
   ptr_lib::shared_ptr<std::vector<uint8_t> > vector_;
 };
diff --git a/ndn-cpp/util/signed-blob.hpp b/ndn-cpp/util/signed-blob.hpp
index 62e6ee2..dd94ae0 100644
--- a/ndn-cpp/util/signed-blob.hpp
+++ b/ndn-cpp/util/signed-blob.hpp
@@ -34,7 +34,7 @@
    * @param signedPortionEndOffset The offset in the encoding of the end of the signed portion.
    */
   SignedBlob
-    (const uint8_t* value, unsigned int valueLength, unsigned int signedPortionBeginOffset, unsigned int signedPortionEndOffset)
+    (const uint8_t* value, size_t valueLength, size_t signedPortionBeginOffset, size_t signedPortionEndOffset)
   : Blob(value, valueLength), signedPortionBeginOffset_(signedPortionBeginOffset), signedPortionEndOffset_(signedPortionEndOffset)
   {
   }
@@ -48,7 +48,7 @@
    * @param signedPortionEndOffset The offset in the encoding of the end of the signed portion.
    */
   SignedBlob
-    (const std::vector<uint8_t> &value, unsigned int signedPortionBeginOffset, unsigned int signedPortionEndOffset)
+    (const std::vector<uint8_t> &value, size_t signedPortionBeginOffset, size_t signedPortionEndOffset)
   : Blob(value), signedPortionBeginOffset_(signedPortionBeginOffset), signedPortionEndOffset_(signedPortionEndOffset)
   {
   }
@@ -62,13 +62,13 @@
    */
   SignedBlob
     (const ptr_lib::shared_ptr<std::vector<uint8_t> > &value, 
-     unsigned int signedPortionBeginOffset, unsigned int signedPortionEndOffset)
+     size_t signedPortionBeginOffset, size_t signedPortionEndOffset)
   : Blob(value), signedPortionBeginOffset_(signedPortionBeginOffset), signedPortionEndOffset_(signedPortionEndOffset)
   {
   }
   SignedBlob
     (const ptr_lib::shared_ptr<const std::vector<uint8_t> > &value, 
-     unsigned int signedPortionBeginOffset, unsigned int signedPortionEndOffset)
+     size_t signedPortionBeginOffset, size_t signedPortionEndOffset)
   : Blob(value), signedPortionBeginOffset_(signedPortionBeginOffset), signedPortionEndOffset_(signedPortionEndOffset)
   {
   }
@@ -76,7 +76,7 @@
   /**
    * Return the length of the signed portion of the immutable byte array, or 0 of the pointer to the array is null.
    */
-  unsigned int 
+  size_t 
   signedSize() const
   {
     if (*this)
@@ -101,18 +101,18 @@
   /**
    * Return the offset in the array of the beginning of the signed portion.
    */  
-  unsigned int 
+  size_t 
   getSignedPortionBeginOffset() { return signedPortionBeginOffset_; }
 
   /**
    * Return the offset in the array of the end of the signed portion.
    */  
-  unsigned int 
+  size_t 
   getSignedPortionEndOffset() { return signedPortionEndOffset_; }
   
 private:
-  unsigned int signedPortionBeginOffset_;
-  unsigned int signedPortionEndOffset_;
+  size_t signedPortionBeginOffset_;
+  size_t signedPortionEndOffset_;
 };
 
 }