diff --git a/src/security/digest-sha256.cpp b/src/security/digest-sha256.cpp
index bbe2e10..3c8867c 100644
--- a/src/security/digest-sha256.cpp
+++ b/src/security/digest-sha256.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
-/**
- * Copyright (c) 2013-2015 Regents of the University of California.
+/*
+ * Copyright (c) 2013-2017 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -32,7 +32,7 @@
   : Signature(signature)
 {
   if (getType() != tlv::DigestSha256)
-    BOOST_THROW_EXCEPTION(Error("Incorrect signature type"));
+    BOOST_THROW_EXCEPTION(Error("Cannot construct DigestSha256 from SignatureType " + to_string(getType())));
 }
 
 } // namespace ndn
diff --git a/src/security/digest-sha256.hpp b/src/security/digest-sha256.hpp
index d3a15de..fe226d8 100644
--- a/src/security/digest-sha256.hpp
+++ b/src/security/digest-sha256.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
-/**
- * Copyright (c) 2013-2014 Regents of the University of California.
+/*
+ * Copyright (c) 2013-2017 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -22,34 +22,29 @@
 #ifndef NDN_SECURITY_DIGEST_SHA256_HPP
 #define NDN_SECURITY_DIGEST_SHA256_HPP
 
-#include "../data.hpp"
-#include "../encoding/tlv.hpp"
+#include "../signature.hpp"
 
 namespace ndn {
 
-/**
- * Represent a SHA256 digest.
+/** @brief Represents a signature of DigestSha256 type
+ *
+ *  This signature type provides integrity protection using SHA-256 digest, but no provenance of a
+ *  Data packet or any kind of guarantee that packet is from the original source.
  */
 class DigestSha256 : public Signature
 {
 public:
-  class Error : public Signature::Error
-  {
-  public:
-    explicit
-    Error(const std::string& what)
-      : Signature::Error(what)
-    {
-    }
-  };
-
+  /** @brief Create empty DigestSha256 signature
+   */
   DigestSha256();
 
+  /** @brief Convert base Signature to DigestSha256 signature
+   *  @throw Signature::Error SignatureType is not DigestSha256
+   */
   explicit
   DigestSha256(const Signature& signature);
-
 };
 
 } // namespace ndn
 
-#endif //NDN_SECURITY_DIGEST_SHA256_HPP
+#endif // NDN_SECURITY_DIGEST_SHA256_HPP
diff --git a/src/security/signature-sha256-with-ecdsa.cpp b/src/security/signature-sha256-with-ecdsa.cpp
index 72a5acd..bb86839 100644
--- a/src/security/signature-sha256-with-ecdsa.cpp
+++ b/src/security/signature-sha256-with-ecdsa.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
-/**
- * Copyright (c) 2013-2015 Regents of the University of California.
+/*
+ * Copyright (c) 2013-2017 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -32,17 +32,17 @@
   : Signature(signature)
 {
   if (getType() != tlv::SignatureSha256WithEcdsa)
-    BOOST_THROW_EXCEPTION(Error("Incorrect signature type"));
+    BOOST_THROW_EXCEPTION(Error("Cannot construct Sha256WithEcdsa from SignatureType " + to_string(getType())));
 
   if (!hasKeyLocator()) {
-    BOOST_THROW_EXCEPTION(Error("KeyLocator is missing"));
+    BOOST_THROW_EXCEPTION(Error("KeyLocator is missing in Sha256WithEcdsa signature"));
   }
 }
 
 void
 SignatureSha256WithEcdsa::unsetKeyLocator()
 {
-  BOOST_THROW_EXCEPTION(Error("KeyLocator cannot be reset for SignatureSha256WithEcdsa"));
+  BOOST_THROW_EXCEPTION(Error("KeyLocator cannot be unset in Sha256WithEcdsa signature"));
 }
 
 } // namespace ndn
diff --git a/src/security/signature-sha256-with-ecdsa.hpp b/src/security/signature-sha256-with-ecdsa.hpp
index 4b0eb7f..c75ffc9 100644
--- a/src/security/signature-sha256-with-ecdsa.hpp
+++ b/src/security/signature-sha256-with-ecdsa.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
-/**
- * Copyright (c) 2013-2014 Regents of the University of California.
+/*
+ * Copyright (c) 2013-2017 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -26,33 +26,32 @@
 
 namespace ndn {
 
-/**
- * represents a Sha256WithEcdsa signature.
+/** @brief Represents a signature of Sha256WithEcdsa type
+ *
+ *  This signature type provides integrity and provenance protection using an ECDSA signature over a
+ *  SHA-256 digest.
  */
 class SignatureSha256WithEcdsa : public Signature
 {
 public:
-  class Error : public Signature::Error
-  {
-  public:
-    explicit
-    Error(const std::string& what)
-      : Signature::Error(what)
-    {
-    }
-  };
-
+  /** @brief Create Sha256WithEcdsa signature with specified KeyLocator
+   */
   explicit
   SignatureSha256WithEcdsa(const KeyLocator& keyLocator = KeyLocator());
 
+  /** @brief Convert base Signature to Sha256WithEcdsa signature
+   *  @throw Signature::Error SignatureType is not Sha256WithEcdsa
+   */
   explicit
   SignatureSha256WithEcdsa(const Signature& signature);
 
 private:
+  /** @brief Prevent unsetting KeyLocator
+   */
   void
   unsetKeyLocator();
 };
 
 } // namespace ndn
 
-#endif //NDN_SECURITY_SIGNATURE_SHA256_WITH_ECDSA_HPP
+#endif // NDN_SECURITY_SIGNATURE_SHA256_WITH_ECDSA_HPP
diff --git a/src/security/signature-sha256-with-rsa.cpp b/src/security/signature-sha256-with-rsa.cpp
index 72f5c8b..97946f8 100644
--- a/src/security/signature-sha256-with-rsa.cpp
+++ b/src/security/signature-sha256-with-rsa.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
-/**
- * Copyright (c) 2013-2015 Regents of the University of California.
+/*
+ * Copyright (c) 2013-2017 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -32,17 +32,17 @@
   : Signature(signature)
 {
   if (getType() != tlv::SignatureSha256WithRsa)
-    BOOST_THROW_EXCEPTION(Error("Incorrect signature type"));
+    BOOST_THROW_EXCEPTION(Error("Cannot construct Sha256WithRsa from SignatureType " + to_string(getType())));
 
   if (!hasKeyLocator()) {
-    BOOST_THROW_EXCEPTION(Error("KeyLocator is missing"));
+    BOOST_THROW_EXCEPTION(Error("KeyLocator is missing in Sha256WithRsa signature"));
   }
 }
 
 void
 SignatureSha256WithRsa::unsetKeyLocator()
 {
-  BOOST_THROW_EXCEPTION(Error("KeyLocator cannot be reset for SignatureSha256WithRsa"));
+  BOOST_THROW_EXCEPTION(Error("KeyLocator cannot be unset in Sha256WithRsa signature"));
 }
 
 } // namespace ndn
diff --git a/src/security/signature-sha256-with-rsa.hpp b/src/security/signature-sha256-with-rsa.hpp
index 937794b..2466018 100644
--- a/src/security/signature-sha256-with-rsa.hpp
+++ b/src/security/signature-sha256-with-rsa.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
-/**
- * Copyright (c) 2013-2014 Regents of the University of California.
+/*
+ * Copyright (c) 2013-2017 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -26,33 +26,32 @@
 
 namespace ndn {
 
-/**
- * Represent a SHA256-with-RSA signature.
+/** @brief Represents a signature of Sha256WithRsa type
+ *
+ *  This signature type provides integrity and provenance protection using a RSA signature over a
+ *  SHA-256 digest.
  */
 class SignatureSha256WithRsa : public Signature
 {
 public:
-  class Error : public Signature::Error
-  {
-  public:
-    explicit
-    Error(const std::string& what)
-      : Signature::Error(what)
-    {
-    }
-  };
-
+  /** @brief Create Sha256WithRsa signature with specified KeyLocator
+   */
   explicit
   SignatureSha256WithRsa(const KeyLocator& keyLocator = KeyLocator());
 
+  /** @brief Convert base Signature to Sha256WithRsa signature
+   *  @throw Signature::Error SignatureType is not Sha256WithRsa
+   */
   explicit
   SignatureSha256WithRsa(const Signature& signature);
 
 private:
+  /** @brief Prevent unsetting KeyLocator
+   */
   void
   unsetKeyLocator();
 };
 
 } // namespace ndn
 
-#endif //NDN_SECURITY_SIGNATURE_SHA256_WITH_RSA_HPP
+#endif // NDN_SECURITY_SIGNATURE_SHA256_WITH_RSA_HPP