diff --git a/07.md b/07.md
index 8ebb4d99..559d4826 100644
--- a/07.md
+++ b/07.md
@@ -12,6 +12,7 @@ That object must define the following methods:
 
 ```
 async window.nostr.getPublicKey(): string // returns a public key as hex
+async window.nostr.getDerivedKey(key: string): string // returns a key derived from hmac(key, prvkey).
 async window.nostr.signEvent(event: Event): Event // takes an event object, adds `id`, `pubkey` and `sig` and returns it
 ```