security: Add v2::Validator implementation

Based on the code originally written by Qiuhan Ding

Change-Id: Ib66e24f49d0b6fb2ae21ea1fca7b9ec62ecb753a
Refs: #3289, #1872
diff --git a/docs/tutorials/security-library.rst b/docs/tutorials/security-library.rst
index 8ee8d40..1da1e61 100644
--- a/docs/tutorials/security-library.rst
+++ b/docs/tutorials/security-library.rst
@@ -132,7 +132,7 @@
 ~~~~~~~~~~~~~~~~~~~~
 
 One can call :ndn-cxx:`KeyChain::generateRsaKeyPair` to generate an RSA key pair or
-:ndn-cxx:`KeyChain::generateEcdsaKeyPair` to generate an ECDSA key.  Note that generated
+:ndn-cxx:`KeyChain::generateEcKeyPair` to generate an EC key.  Note that generated
 key pair is not set as the default key of the identity, so you need to set it manually by
 calling :ndn-cxx:`KeyChain::setDefaultKeyNameForIdentity`. There is also a helper method
 :ndn-cxx:`KeyChain::generateRsaKeyPairAsDefault`, which combines the two steps into one.