Imagine a relay with countless mailboxes, each with a unique number. For parties already engaged in double ratchet algorithm chat, only they know the value of the latest DH ratchet. This value can be used to derive a receiving address (mailbox number) that only they know. The chatting parties simply need to go to this mailbox to retrieve messages.

Since only the chatting parties know the latest mailbox number, even if the sending address is random, as long as the mailbox number is correct, they can confirm that it comes from their chat partner.

Therefore, the mechanism for determining the receiving address is most important, while the sending address can be randomly generated. nostr:note10mmy7ru7perkhe9lavl7rlvpqd9a0knvz8ukhx7hhlc8zqtrhceqsaxxjm