crates/nip4e/src/lib.rs

@@ -39,7 +39,7 @@ pub enum DeviceEvent {
     /// User have not setup encryption key
     NotSet,
     /// The device is requesting an encryption key
-    Requesting,
+    Requesting(SharedString),
     /// An error occurred
     Error(SharedString),
 }
@@ -319,10 +319,7 @@ impl DeviceRegistry {
         cx.background_spawn(async move {
             // Construct an announcement event
             let event = EventBuilder::new(Kind::Custom(10044), "")
-                .tags(vec![
+                .tag(Tag::custom("n", vec![n]))
-                    Tag::custom("n", vec![n]),
-                    Tag::custom("client", vec![CLIENT_NAME]),
-                ])
                 .finalize_async(&signer)
                 .await?;
 
@@ -433,10 +430,7 @@ impl DeviceRegistry {
 
             // No usable approval event found, construct a request event
             let event = EventBuilder::new(Kind::Custom(4454), "")
-                .tags(vec![
+                .tags(vec![Tag::custom("P", vec![app_pubkey])])
-                    Tag::custom("P", vec![app_pubkey]),
-                    Tag::custom("client", vec![CLIENT_NAME]),
-                ])
                 .finalize_async(&signer)
                 .await?;
 
@@ -475,8 +469,6 @@ impl DeviceRegistry {
         let signer = nostr.read(cx).signer();
         let app_keys_task = get_or_init_app_keys(cx);
 
-        cx.emit(DeviceEvent::Requesting);
-
         self.tasks.push(cx.spawn(async move |this, cx| {
             let app_keys = match app_keys_task.await {
                 Ok(app_keys) => app_keys,
@@ -488,6 +480,12 @@ impl DeviceRegistry {
                 }
             };
 
+            this.update(cx, |_this, cx| {
+                cx.emit(DeviceEvent::Requesting(authorization_code(
+                    &app_keys.public_key(),
+                )));
+            })?;
+
             let task: Task<Result<(), Error>> = cx.background_spawn(async move {
                 let public_key = signer.get_public_key_async().await?;
 
@@ -694,7 +692,9 @@ impl DeviceRegistry {
     /// Build a notification for the encryption request.
     fn notification(&self, event: Event, cx: &Context<Self>) -> Result<Notification, Error> {
         const MSG: &str = "You've requested an encryption key from another device. \
-                           Approve to allow Coop to share with it.";
+                           Approve to allow Coop to share with it. Before approving, \
+                           compare the code with the one shown on the requesting \
+                           device.";
 
         let requester = event
             .tags
@@ -704,16 +704,10 @@ impl DeviceRegistry {
             .and_then(|content| PublicKey::parse(content).ok())
             .context("Request has no valid requester key")?;
 
-        let client_name = event
+        let code = authorization_code(&requester);
-            .tags
-            .iter()
-            .find(|tag| tag.kind() == "client")
-            .and_then(|tag| tag.content())
-            .map(|c| c.to_string());
-
-        let request = Announcement::new(requester, client_name);
         let persons = PersonRegistry::global(cx);
         let profile = persons.read(cx).get(&requester, cx);
+        let code_label = code.clone();
 
         let entity = cx.entity().downgrade();
         let loading = Rc::new(Cell::new(false));
@@ -776,7 +770,7 @@ impl DeviceRegistry {
                                             .font_semibold()
                                             .text_xs()
                                             .text_color(cx.theme().text_muted)
-                                            .child(SharedString::from("Client:")),
+                                            .child(SharedString::from("Code:")),
                                     )
                                     .child(
                                         div()
@@ -785,7 +779,7 @@ impl DeviceRegistry {
                                             .px_2()
                                             .rounded(cx.theme().radius)
                                             .bg(cx.theme().elevated_surface_background)
-                                            .child(request.client_name()),
+                                            .child(code_label.clone()),
                                     ),
                             ),
                     )
@@ -817,6 +811,13 @@ impl DeviceRegistry {
 
 struct DeviceNotification;
 
+/// The first eight hexadecimal characters of the client public key.
+fn authorization_code(public_key: &PublicKey) -> SharedString {
+    let hex = public_key.to_hex();
+    let code = hex[..8].to_uppercase();
+    SharedString::from(format!("{} {}", &code[..4], &code[4..]))
+}
+
 /// Get or create new app keys (async, returns a task)
 fn get_or_init_app_keys(cx: &App) -> Task<Result<Keys, Error>> {
     let read = cx.read_credentials(CLIENT_NAME);

crates/state/src/nip4e.rs

@@ -1,4 +1,3 @@
-use gpui::SharedString;
 use nostr_sdk::prelude::*;
 
 /// Announcement
@@ -6,12 +5,12 @@ use nostr_sdk::prelude::*;
 pub struct Announcement {
     /// The public key of the device that created this announcement.
     public_key: PublicKey,
-
-    /// The name of the device that created this announcement.
-    client_name: Option<String>,
 }
 
 impl Announcement {
+    /// Parse an announcement from an event, returning `None` when the `n`
+    /// tag is missing or malformed so callers never mistake the author's
+    /// identity key for an encryption key.
     pub fn from_event(event: &Event) -> Option<Self> {
         let public_key = event
             .tags
@@ -20,33 +19,15 @@ impl Announcement {
             .and_then(|tag| tag.content())
             .and_then(|c| PublicKey::parse(c).ok())?;
 
-        let client_name = event
+        Some(Self { public_key })
-            .tags
-            .iter()
-            .find(|tag| tag.kind() == "client")
-            .and_then(|tag| tag.content())
-            .map(|c| c.to_string());
-
-        Some(Self::new(public_key, client_name))
     }
 
-    pub fn new(public_key: PublicKey, client_name: Option<String>) -> Self {
+    pub fn new(public_key: PublicKey) -> Self {
-        Self {
+        Self { public_key }
-            public_key,
-            client_name,
-        }
     }
 
     /// Returns the public key of the device that created this announcement.
     pub fn public_key(&self) -> PublicKey {
         self.public_key
     }
-
-    /// Returns the client name of the device that created this announcement.
-    pub fn client_name(&self) -> SharedString {
-        self.client_name
-            .as_ref()
-            .map(SharedString::from)
-            .unwrap_or(SharedString::from("Unknown"))
-    }
 }

crates/workspace/src/lib.rs

@@ -106,14 +106,15 @@ impl Workspace {
             // Observe all events emitted by the device registry
             cx.subscribe_in(&device, window, |_this, _device, event, window, cx| {
                 match event {
-                    DeviceEvent::Requesting => {
+                    DeviceEvent::Requesting(code) => {
-                        const MSG: &str =
+                        const MSG: &str = "Please open another client and approve the request \
-                            "Please open other client and approve the request for encryption key.";
+                                           for the encryption key. Compare the code with the \
+                                           one shown there before approving.";
 
                         let note = Notification::new()
                             .id::<DeviceNotifcation>()
                             .autohide(false)
-                            .title("Wait for approval")
+                            .title(format!("Wait for approval · {code}"))
                             .message(MSG)
                             .with_kind(NotificationKind::Info);
 

docs/nip4e-audit.md

@@ -23,9 +23,13 @@
 > pubkey, the 4454 notification parses the requester key from the `P` tag, the
 > NotSet "Retry" button re-checks for an announcement instead of silently
 > generating (rotating) a new encryption key, and the restore dialog's
-> inverted empty-key check is fixed. Still open: the remaining security notes
+> inverted empty-key check is fixed. Additionally, the `client` tag and
-> in section 4 (plaintext backup file, one-click approval without a
+> `client_name` were dropped from announcements/requests, and the PsstPsst
-> verification code).
+> authorization code was adapted: both sides display the first 8 hex chars of
+> the requester client pubkey (`XXXX XXXX`) — the approver in the request
+> notification, the requester in the "Wait for approval" notification — so the
+> transfer can be verified out of band before approving. Still open: the
+> plaintext backup file in section 4.
 
 **Scope**: `crates/nip4e/src/lib.rs` (key announcement/sync), the send path (`crates/chat/src/room.rs`), the receive path (`crates/chat/src/lib.rs`), UI integration (`crates/workspace`), compared against the [NIP-4e draft](https://github.com/nostr-protocol/nips/blob/per-device-keys/4e.md) and [PsstPsst's implementation](https://github.com/CodyTseng/psstpsst) (`docs/protocols/nip4e.md` + `docs/protocols/nip17-extensions.md`, plus rust-nostr's NIP-59 source to verify crypto mechanics).