diff --git a/common/protocol/account.go b/common/protocol/account.go
index f251d5b35..1c6a1eeaa 100644
--- a/common/protocol/account.go
+++ b/common/protocol/account.go
@@ -1,11 +1,11 @@
 package protocol
 
+// Account is an user identity used for authentication.
 type Account interface {
 	Equals(Account) bool
 }
 
+// AsAccount is an object can be converted into account.
 type AsAccount interface {
 	AsAccount() (Account, error)
 }
-
-type NewAccountFactory func() AsAccount