diff --git a/include/jwt/algorithm.hpp b/include/jwt/algorithm.hpp
index 83e8535..c7e59fb 100644
--- a/include/jwt/algorithm.hpp
+++ b/include/jwt/algorithm.hpp
@@ -1,6 +1,13 @@
 #ifndef CPP_JWT_ALGORITHM_HPP
 #define CPP_JWT_ALGORITHM_HPP
 
+/*!
+ * Most of the signing and verification code has been taken
+ * and modified for C++ specific use from the C implementation
+ * JWT library, libjwt.
+ * https://github.com/benmcollins/libjwt/tree/master/libjwt
+ */
+
 #include <cassert>
 #include <system_error>
 
@@ -12,7 +19,9 @@
 #include <openssl/ecdsa.h>
 #include <openssl/buffer.h>
 
+#include "jwt/exceptions.hpp"
 #include "jwt/string_view.hpp"
+#include "jwt/error_codes.hpp"
 
 namespace jwt {
 
@@ -20,23 +29,25 @@ namespace jwt {
 using sign_result_t = std::pair<std::string, std::error_code>;
 /// The result type of verification function
 using verify_result_t = std::pair<bool, std::error_code>;
-/// The function pointer type of the signing function
+/// The function pointer type for the signing function
 using sign_func_t   = sign_result_t (*) (const string_view key, 
                                          const string_view data);
-///
+/// The function pointer type for the verifying function
 using verify_func_t = verify_result_t (*) (const string_view key,
                                            const string_view head,
                                            const string_view jwt_sign);
 
 namespace algo {
 
-//TODO: All these can be done using code generaion.
-// NO. NEVER. I hate Macros.
-// You can use templates too.
-// No. I would rather prefer explicit.
-// Ok. You win.
+//Me: TODO: All these can be done using code generaion.
+//Me: NO. NEVER. I hate Macros.
+//Me: You can use templates too.
+//Me: No. I would rather prefer explicit.
+//Me: Ok. You win.
+//Me: Same to you.
 
-/*!
+/**
+ * HS256 algorithm.
  */
 struct HS256
 {
@@ -46,7 +57,8 @@ struct HS256
   }
 };
 
-/*!
+/**
+ * HS384 algorithm.
  */
 struct HS384
 {
@@ -56,7 +68,8 @@ struct HS384
   }
 };
 
-/*!
+/**
+ * HS512 algorithm.
  */
 struct HS512
 {
@@ -66,7 +79,8 @@ struct HS512
   }
 };
 
-/*!
+/**
+ * NONE algorithm.
  */
 struct NONE
 {
@@ -76,7 +90,8 @@ struct NONE
   }
 };
 
-/*!
+/**
+ * RS256 algorithm.
  */
 struct RS256
 {
@@ -88,7 +103,8 @@ struct RS256
   }
 };
 
-/*!
+/**
+ * RS384 algorithm.
  */
 struct RS384
 {
@@ -100,7 +116,8 @@ struct RS384
   }
 };
 
-/*!
+/**
+ * RS512 algorithm.
  */
 struct RS512
 {
@@ -112,7 +129,8 @@ struct RS512
   }
 };
 
-/*!
+/**
+ * ES256 algorithm.
  */
 struct ES256
 {
@@ -124,7 +142,8 @@ struct ES256
   }
 };
 
-/*!
+/**
+ * ES384 algorithm.
  */
 struct ES384
 {
@@ -136,7 +155,8 @@ struct ES384
   }
 };
 
-/*!
+/**
+ * ES512 algorithm.
  */
 struct ES512
 {
@@ -151,8 +171,8 @@ struct ES512
 } //END Namespace algo
 
 
-/*!
- * JWT signing algorithm.
+/**
+ * JWT signing algorithm types.
  */
 enum class algorithm
 {
@@ -170,7 +190,9 @@ enum class algorithm
 };
 
 
-/*!
+/**
+ * Convert the algorithm enum class type to
+ * its stringified form.
  */
 string_view alg_to_str(enum algorithm alg) noexcept
 {
@@ -192,7 +214,9 @@ string_view alg_to_str(enum algorithm alg) noexcept
   assert (0 && "Code not reached");
 }
 
-/*!
+/**
+ * Convert stringified algorithm to enum class.
+ * The string comparison is case insesitive.
  */
 enum algorithm str_to_alg(const string_view alg) noexcept
 {
@@ -213,7 +237,14 @@ enum algorithm str_to_alg(const string_view alg) noexcept
 }
 
 
-/*!
+/**
+ * OpenSSL HMAC based signature and verfication.
+ *
+ * The template type `Hasher` takes the type representing
+ * the HMAC algorithm type from the `jwt::algo` namespace.
+ *
+ * The struct is specialized for NONE algorithm. See the
+ * details of that class as well.
  */
 template <typename Hasher>
 struct HMACSign
@@ -221,7 +252,18 @@ struct HMACSign
   /// The type of Hashing algorithm
   using hasher_type = Hasher;
 
-  /*!
+  /**
+   * Signs the input using the HMAC algorithm using the
+   * provided key.
+   *
+   * Arguments:
+   *  @key : The secret/key to use for the signing.
+   *         Cannot be empty string.
+   *  @data : The data to be signed.
+   *
+   *  Exceptions:
+   *    Any allocation failure will result in jwt::MemoryAllocationException
+   *    being thrown.
    */
   static sign_result_t sign(const string_view key, const string_view data)
   {
@@ -240,39 +282,55 @@ struct HMACSign
                               &len);
 
     if (!res) {
-      //TODO: Set the appropriate error code
+      ec = AlgorithmErrc::SigningErr;
     }
-    sign.resize(len);
 
-    return {std::move(sign), ec};
+    sign.resize(len);
+    return { std::move(sign), ec };
   }
 
-  /*!
+  /**
    */
   static verify_result_t 
   verify(const string_view key, const string_view head, const string_view sign);
 
 };
 
-/*!
+/**
+ * Specialization of `HMACSign` class
+ * for NONE algorithm.
+ *
+ * This specialization is selected for even
+ * PEM based algorithms.
+ *
+ * The signing and verification APIs are
+ * basically no-op except that they would 
+ * set the relevant error code.
+ *
+ * NOTE: error_code would be set in the case 
+ * of usage of NONE algorithm.
+ * Users of this API are expected to check for
+ * the case explicitly.
  */
 template <>
 struct HMACSign<algo::NONE>
 {
   using hasher_type = algo::NONE;
 
-  /*!
+  /**
+   * Basically a no-op. Sets the error code to NoneAlgorithmUsed.
    */
   static sign_result_t sign(const string_view key, const string_view data)
   {
-    std::string sign;
+    (void)key;
+    (void)data;
     std::error_code ec{};
+    ec = AlgorithmErrc::NoneAlgorithmUsed;
 
-    //TODO: Set the appropriate error code for none
-    return {sign, ec};
+    return { std::string{}, ec };
   }
 
-  /*!
+  /**
    */
   static verify_result_t
   verify(const string_view key, const string_view head, const string_view sign)
@@ -281,13 +339,21 @@ struct HMACSign<algo::NONE>
     std::error_code ec{};
 
     //TODO: Set the appropriate error code for none
-    return {compare_res, ec};
+    return { compare_res, ec };
   }
 
 };
 
 
-/*!
+
+/**
+ * OpenSSL PEM based signature and verfication.
+ *
+ * The template type `Hasher` takes the type representing
+ * the PEM algorithm type from the `jwt::algo` namespace.
+ *
+ * For NONE algorithm, HMACSign<> specialization is used.
+ * See that for more details.
  */
 template <typename Hasher>
 struct PEMSign
@@ -296,7 +362,17 @@ public:
   /// The type of Hashing algorithm
   using hasher_type = Hasher;
 
-  /*!
+  /**
+   * Signs the input data using PEM encryption algorithm.
+   *
+   * Arguments:
+   *  @key : The key/secret to be used for signing.
+   *         Cannot be an empty string.
+   *  @data: The data to be signed.
+   *
+   * Exceptions:
+   *  Any allocation failure would be thrown out as
+   *  jwt::MemoryAllocationException.
    */
   static sign_result_t sign(const string_view key, const string_view data)
   {
@@ -307,27 +383,20 @@ public:
     };
 
     std::unique_ptr<EVP_PKEY, decltype(evpkey_deletor)>
-      pkey{load_key(key), evpkey_deletor};
+      pkey{load_key(key, ec), evpkey_deletor};
 
-    if (!pkey) {
-      //TODO: set valid error code
-      return {std::string{}, ec};
-    }
+    if (ec) return { std::string{}, ec };
 
     //TODO: Use stack string here ?
     std::string sign = evp_digest(pkey.get(), data, ec);
-    if (ec) {
-      //TODO: handle error_code
-      return {std::move(sign), ec};
-    }
 
-    if (Hasher::type != EVP_PKEY_EC) {
-      return {std::move(sign), ec};
-    } else {
+    if (ec) return { std::string{}, ec };
+
+    if (Hasher::type == EVP_PKEY_EC) {
       sign = public_key_ser(pkey.get(), sign, ec);
     }
 
-    return {std::move(sign), ec};
+    return { std::move(sign), ec };
   }
 
   /*!
@@ -345,7 +414,7 @@ public:
 private:
   /*!
    */
-  static EVP_PKEY* load_key(const string_view key);
+  static EVP_PKEY* load_key(const string_view key, std::error_code& ec);
 
   /*!
    */
diff --git a/include/jwt/error_codes.hpp b/include/jwt/error_codes.hpp
index e69de29..b7357e4 100644
--- a/include/jwt/error_codes.hpp
+++ b/include/jwt/error_codes.hpp
@@ -0,0 +1,44 @@
+#ifndef CPP_JWT_ERROR_CODES_HPP
+#define CPP_JWT_ERROR_CODES_HPP
+
+#include <system_error>
+
+namespace jwt {
+/**
+ * All the algorithm errors
+ */
+enum class AlgorithmErrc
+{
+  SigningErr = 1,
+  VerificationErr,
+  NoneAlgorithmUsed, // Not an actual error!
+};
+
+/**
+ * Algorithm error conditions
+ */
+enum class AlgorithmFailureSource
+{
+};
+
+
+/**
+ */
+std::error_code make_error_code(AlgorithmErrc err);
+
+} // END namespace jwt
+
+
+/**
+ * Make the custom enum classes as error code
+ * adaptable.
+ */
+namespace std
+{
+  template <>
+  struct is_error_code_enum<jwt::AlgorithmErrc> : true_type {};
+}
+
+#include "jwt/impl/error_codes.ipp"
+
+#endif
diff --git a/include/jwt/exceptions.hpp b/include/jwt/exceptions.hpp
index e69de29..14863e2 100644
--- a/include/jwt/exceptions.hpp
+++ b/include/jwt/exceptions.hpp
@@ -0,0 +1,35 @@
+#ifndef CPP_JWT_EXCEPTIONS_HPP
+#define CPP_JWT_EXCEPTIONS_HPP
+
+#include <new>
+
+namespace jwt {
+
+/**
+ */
+class MemoryAllocationException final: public std::bad_alloc
+{
+public:
+  /**
+   * Construct MemoryAllocationException from a
+   * string literal.
+   */
+  template <size_t N>
+  MemoryAllocationException(const char(&msg)[N])
+    : msg_(&msg[0])
+  {
+  }
+
+  virtual const char* what() const noexcept override
+  {
+    return msg_;
+  }
+
+private:
+  const char* msg_ = nullptr;
+};
+
+
+} // END namespace jwt
+
+#endif
diff --git a/include/jwt/impl/algorithm.ipp b/include/jwt/impl/algorithm.ipp
index 0eb4480..16b5a7e 100644
--- a/include/jwt/impl/algorithm.ipp
+++ b/include/jwt/impl/algorithm.ipp
@@ -12,6 +12,7 @@ verify_result_t HMACSign<Hasher>::verify(
     const string_view jwt_sign)
 {
   std::error_code ec{};
+  //TODO: remove these static deletors.
   static auto bio_deletor = [](BIO* ptr) {
     if (ptr) BIO_free_all(ptr);
   };
@@ -77,21 +78,27 @@ verify_result_t HMACSign<Hasher>::verify(
 }
 
 template <typename Hasher>
-EVP_PKEY* PEMSign<Hasher>::load_key(const string_view key)
+EVP_PKEY* PEMSign<Hasher>::load_key(
+    const string_view key,
+    std::error_code& ec)
 {
-  auto bio_deletor = [](BIO* ptr) {
+  static auto bio_deletor = [](BIO* ptr) {
     if (ptr) BIO_free(ptr);
   };
 
+  ec.clear();
+
   std::unique_ptr<BIO, decltype(bio_deletor)>
     bio_ptr{BIO_new_mem_buf((void*)key.data(), key.length()), bio_deletor};
 
   if (!bio_ptr) {
-    return nullptr;
+    throw MemoryAllocationException("BIO_new_mem_buf failed");
   }
 
   EVP_PKEY* pkey = PEM_read_bio_PrivateKey(bio_ptr.get(), nullptr, nullptr, nullptr);
+
   if (!pkey) {
+    ec = AlgorithmErrc::SigningErr;
     return nullptr;
   }
 
@@ -104,36 +111,37 @@ std::string PEMSign<Hasher>::evp_digest(
     const string_view data, 
     std::error_code& ec)
 {
-  auto md_deletor = [](EVP_MD_CTX* ptr) {
+  static auto md_deletor = [](EVP_MD_CTX* ptr) {
     if (ptr) EVP_MD_CTX_destroy(ptr);
   };
 
+  ec.clear();
+
   std::unique_ptr<EVP_MD_CTX, decltype(md_deletor)>
     mdctx_ptr{EVP_MD_CTX_create(), md_deletor};
 
   if (!mdctx_ptr) {
-    //TODO: set appropriate error_code
-    return std::string{};
+    throw MemoryAllocationException("EVP_MD_CTX_create failed");
   }
 
   //Initialiaze the digest algorithm
   if (EVP_DigestSignInit(
         mdctx_ptr.get(), nullptr, Hasher{}(), nullptr, pkey) != 1) {
-    //TODO: set appropriate error_code
-    return std::string{};
+    ec = AlgorithmErrc::SigningErr;
+    return {};
   }
 
   //Update the digest with the input data
   if (EVP_DigestSignUpdate(mdctx_ptr.get(), data.data(), data.length()) != 1) {
-    //TODO: set appropriate error_code
+    ec = AlgorithmErrc::SigningErr;
     return std::string{};
   }
 
   unsigned long len = 0;
 
   if (EVP_DigestSignFinal(mdctx_ptr.get(), nullptr, &len) != 1) {
-    //TODO: set appropriate error_code
-    return std::string{};
+    ec = AlgorithmErrc::SigningErr;
+    return {};
   }
 
   std::string sign;
@@ -141,8 +149,8 @@ std::string PEMSign<Hasher>::evp_digest(
 
   //Get the signature
   if (EVP_DigestSignFinal(mdctx_ptr.get(), (unsigned char*)&sign[0], &len) != 1) {
-    //TODO: set appropriate error_code
-    return std::string{};
+    ec = AlgorithmErrc::SigningErr;
+    return {};
   }
 
   return sign;
@@ -157,6 +165,7 @@ std::string PEMSign<Hasher>::public_key_ser(
   // Get the EC_KEY representing a public key and
   // (optionaly) an associated private key
   std::string new_sign;
+  ec.clear();
 
   static auto eckey_deletor = [](EC_KEY* ptr) {
     if (ptr) EC_KEY_free(ptr);
@@ -170,8 +179,8 @@ std::string PEMSign<Hasher>::public_key_ser(
     ec_key{EVP_PKEY_get1_EC_KEY(pkey), eckey_deletor};
 
   if (!ec_key) {
-    //TODO set a valid error code
-    return std::string{};
+    ec = AlgorithmErrc::SigningErr;
+    return {};
   }
 
   uint32_t degree = EC_GROUP_get_degree(EC_KEY_get0_group(ec_key.get()));
@@ -183,8 +192,8 @@ std::string PEMSign<Hasher>::public_key_ser(
            ecsig_deletor};
 
   if (!ec_sig) {
-    //TODO set a valid error code
-    return std::string{};
+    ec = AlgorithmErrc::SigningErr;
+    return {};
   }
 
   const BIGNUM* ec_sig_r = nullptr;
@@ -192,7 +201,7 @@ std::string PEMSign<Hasher>::public_key_ser(
 
 #if 1
   //Taken from https://github.com/nginnever/zogminer/issues/39
-  auto ECDSA_SIG_get0 = [](const ECDSA_SIG *sig, const BIGNUM **pr, const BIGNUM **ps)
+  static auto ECDSA_SIG_get0 = [](const ECDSA_SIG *sig, const BIGNUM **pr, const BIGNUM **ps)
   {
     if (pr != nullptr) *pr = sig->r;
     if (ps != nullptr) *ps = sig->s;
@@ -207,8 +216,8 @@ std::string PEMSign<Hasher>::public_key_ser(
   auto bn_len = (degree + 7) / 8;
 
   if ((r_len > bn_len) || (s_len > bn_len)) {
-    //TODO set a valid error code
-    return std::string{};
+    ec = AlgorithmErrc::SigningErr;
+    return {};
   }
 
   auto buf_len = 2 * bn_len;
diff --git a/include/jwt/impl/error_codes.ipp b/include/jwt/impl/error_codes.ipp
new file mode 100644
index 0000000..7b64276
--- /dev/null
+++ b/include/jwt/impl/error_codes.ipp
@@ -0,0 +1,48 @@
+#ifndef CPP_JWT_ERROR_CODES_IPP
+#define CPP_JWT_ERROR_CODES_IPP
+
+namespace jwt {
+// Anonymous namespace
+namespace {
+
+/**
+ */
+struct AlgorithmErrCategory: std::error_category
+{
+  const char* name() const noexcept override
+  {
+    return "algorithms";
+  }
+
+  std::string message(int ev) const override
+  {
+    switch (static_cast<AlgorithmErrc>(ev))
+    {
+    case AlgorithmErrc::SigningErr:
+      return "signing failed";
+    case AlgorithmErrc::VerificationErr:
+      return "verification failed";
+    case AlgorithmErrc::NoneAlgorithmUsed:
+      return "none algorithm used";
+    };
+
+    assert (0 && "Code not reached");
+  }
+};
+
+// Create global object for the error categories
+const AlgorithmErrCategory theAlgorithmErrCategory {};
+
+}
+
+
+// Create the AlgorithmErrc error code
+std::error_code make_error_code(AlgorithmErrc err)
+{
+  return { static_cast<int>(err), theAlgorithmErrCategory };
+}
+
+
+} // END namespace jwt
+
+#endif
diff --git a/include/jwt/test/test_jwt_object b/include/jwt/test/test_jwt_object
index 432dd74..c625eff 100755
Binary files a/include/jwt/test/test_jwt_object and b/include/jwt/test/test_jwt_object differ