diff --git a/src/security/security-common.hpp b/src/security/security-common.hpp
index 8594581..542e169 100644
--- a/src/security/security-common.hpp
+++ b/src/security/security-common.hpp
@@ -33,8 +33,16 @@
 const ssize_t POS_RANDOM_VAL = -3;
 const ssize_t POS_TIMESTAMP = -4;
 
+/** \brief minimal number of components for Command Interest
+ *  \sa https://redmine.named-data.net/projects/ndn-cxx/wiki/CommandInterest
+ */
 const size_t MIN_LENGTH = 4;
 
+/** \brief minimal number of components for Signed Interest
+ *  \sa https://redmine.named-data.net/projects/ndn-cxx/wiki/SignedInterest
+ */
+const size_t MIN_LENGTH_SIG_ONLY = 2;
+
 } // namespace signed_interest
 
 enum class KeyType {