security: support 224-bit and 521-bit NIST elliptic curves

Change-Id: I28d2e5162e1e8fd7261828d435b059093b6989ea
diff --git a/src/security/transform/private-key.hpp b/src/security/transform/private-key.hpp
index fb4978a..e1af107 100644
--- a/src/security/transform/private-key.hpp
+++ b/src/security/transform/private-key.hpp
@@ -257,10 +257,10 @@
 /**
  * @brief Generate a private key according to @p keyParams
  *
- * @note The public key can be derived from the private key.
+ * @note The corresponding public key can be derived from the private key.
  *
  * @throw std::invalid_argument the specified key type is not supported
- * @throw std::runtime_error    key generation fails
+ * @throw PrivateKey::Error     key generation failed
  */
 unique_ptr<PrivateKey>
 generatePrivateKey(const KeyParams& keyParams);