diff --git a/0002-binary-protocol.md b/0002-binary-protocol.md
index 509dc230b913043a33b15ef1bb9f48effdeeefce..90455329e0645e7f00d0545bef4caff37a97f8c8 100644
--- a/0002-binary-protocol.md
+++ b/0002-binary-protocol.md
@@ -127,6 +127,8 @@ Usernames can be used for only one identity registered on the blockchain.
 
 > It will maybe be possible in the future to use a username not used for a long time.
 
+> As explained below, each document contains issuers raw public keys and signatures. We can hash provided public keys to find associated identities.
+
 # 3. Documents
 
 ## 3.1. Document structure