diff --git a/src/lib.rs b/src/lib.rs
index 7ac8cd0..11d92a6 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -4,6 +4,7 @@ pub mod error;
 pub mod filestore;
 pub mod globals;
 pub mod ip;
+mod neg_storage;
 pub mod nostr;
 pub mod reply;
 pub mod tls;
@@ -25,6 +26,7 @@ use hyper::{Request, Response};
 use hyper_tungstenite::tungstenite;
 use hyper_tungstenite::{HyperWebsocket, WebSocketStream};
 use hyper_util::rt::TokioIo;
+use neg_storage::NegentropyStorageVector;
 use pocket_db::Store;
 use pocket_types::{Id, OwnedFilter, Pubkey};
 use speedy::{Readable, Writable};
@@ -215,6 +217,7 @@ async fn websocket_thread(peer: HashedPeer, websocket: HyperWebsocket, origin: S
             let mut ws_service = WebSocketService {
                 peer,
                 subscriptions: HashMap::new(),
+                neg_subscriptions: HashMap::new(),
                 // We start with a 1-page buffer, and grow it if needed.
                 buffer: vec![0; 4096],
                 websocket,
@@ -350,6 +353,7 @@ async fn websocket_thread(peer: HashedPeer, websocket: HyperWebsocket, origin: S
 struct WebSocketService {
     pub peer: HashedPeer,
     pub subscriptions: HashMap<String, Vec<OwnedFilter>>,
+    pub neg_subscriptions: HashMap<String, NegentropyStorageVector>,
     pub buffer: Vec<u8>,
     pub websocket: WebSocketStream<TokioIo<Upgraded>>,
     pub last_message: Instant,
@@ -425,7 +429,7 @@ impl WebSocketService {
             tokio::select! {
                 instant = interval.tick() => {
                     // Drop them if they have no subscriptions
-                    if self.subscriptions.is_empty() {
+                    if self.subscriptions.is_empty() && self.neg_subscriptions.is_empty() {
                         // And they are idle for timeout_seconds with no subscriptions
                         if last_message_at + Duration::from_secs(timeout_seconds) < instant {
                             self.wsclose(ChorusError::TimedOut.into()).await?;
diff --git a/src/neg_storage.rs b/src/neg_storage.rs
new file mode 100644
index 0000000..9df51e4
--- /dev/null
+++ b/src/neg_storage.rs
@@ -0,0 +1,123 @@
+use negentropy::{Bound, Error, Id, Item, NegentropyStorageBase};
+
+// We construct our own NegentropyStorageVector since NegentropyStorageBase
+// is not implemented for a &NegentropyStorageVector upstream
+
+/// Negentropy Storage Vector
+#[derive(Debug, Clone, Default, PartialEq, Eq)]
+pub struct NegentropyStorageVector {
+    items: Vec<Item>,
+    sealed: bool,
+}
+
+impl NegentropyStorageBase for &NegentropyStorageVector {
+    fn size(&self) -> Result<usize, Error> {
+        self.check_sealed()?;
+        Ok(self.items.len())
+    }
+
+    fn get_item(&self, i: usize) -> Result<Option<Item>, Error> {
+        self.check_sealed()?;
+        Ok(self.items.get(i).copied())
+    }
+
+    fn iterate(
+        &self,
+        begin: usize,
+        end: usize,
+        cb: &mut dyn FnMut(Item, usize) -> Result<bool, Error>,
+    ) -> Result<(), Error> {
+        self.check_sealed()?;
+        self.check_bounds(begin, end)?;
+
+        for i in begin..end {
+            if !cb(self.items[i], i)? {
+                break;
+            }
+        }
+
+        Ok(())
+    }
+
+    fn find_lower_bound(&self, mut first: usize, last: usize, value: &Bound) -> usize {
+        let mut count: usize = last - first;
+
+        while count > 0 {
+            let mut it: usize = first;
+            let step: usize = count / 2;
+            it += step;
+
+            if self.items[it] < value.item {
+                it += 1;
+                first = it;
+                count -= step + 1;
+            } else {
+                count = step;
+            }
+        }
+
+        first
+    }
+}
+
+impl NegentropyStorageVector {
+    /// Create new storage
+    #[inline]
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// Create new storage with capacity
+    #[inline]
+    pub fn with_capacity(capacity: usize) -> Self {
+        Self {
+            items: Vec::with_capacity(capacity),
+            sealed: false,
+        }
+    }
+
+    /// Insert item
+    pub fn insert(&mut self, created_at: u64, id: Id) -> Result<(), Error> {
+        if self.sealed {
+            return Err(Error::AlreadySealed);
+        }
+
+        let elem: Item = Item::with_timestamp_and_id(created_at, id);
+        self.items.push(elem);
+
+        Ok(())
+    }
+
+    /// Seal
+    pub fn seal(&mut self) -> Result<(), Error> {
+        if self.sealed {
+            return Err(Error::AlreadySealed);
+        }
+        self.sealed = true;
+
+        self.items.sort();
+        self.items.dedup();
+
+        Ok(())
+    }
+
+    /// Unseal
+    pub fn unseal(&mut self) -> Result<(), Error> {
+        self.sealed = false;
+        Ok(())
+    }
+
+    fn check_sealed(&self) -> Result<(), Error> {
+        if !self.sealed {
+            return Err(Error::NotSealed);
+        }
+        Ok(())
+    }
+
+    fn check_bounds(&self, begin: usize, end: usize) -> Result<(), Error> {
+        if begin > end || end > self.items.len() {
+            return Err(Error::BadRange);
+        }
+        Ok(())
+    }
+}
diff --git a/src/nostr.rs b/src/nostr.rs
index 1861afe..039abb5 100644
--- a/src/nostr.rs
+++ b/src/nostr.rs
@@ -1,10 +1,12 @@
 use crate::error::{ChorusError, Error};
 use crate::globals::GLOBALS;
+use crate::neg_storage::NegentropyStorageVector;
 use crate::reply::{NostrReply, NostrReplyPrefix};
 use crate::WebSocketService;
 use hyper_tungstenite::tungstenite::Message;
+use negentropy::{Bytes, Negentropy};
 use pocket_types::json::{eat_whitespace, json_unescape, verify_char};
-use pocket_types::{Event, Filter, Hll8, Kind, OwnedFilter, Pubkey, Time};
+use pocket_types::{read_hex, Event, Filter, Hll8, Kind, OwnedFilter, Pubkey, Time};
 use url::Url;
 
 impl WebSocketService {
@@ -32,6 +34,12 @@ impl WebSocketService {
             self.close(msg, inpos + 6).await?;
         } else if &input[inpos..inpos + 5] == b"AUTH\"" {
             self.auth(msg, inpos + 5).await?;
+        } else if &input[inpos..inpos + 9] == b"NEG-OPEN\"" {
+            self.neg_open(msg, inpos + 9).await?;
+        } else if &input[inpos..inpos + 8] == b"NEG-MSG\"" {
+            self.neg_msg(msg, inpos + 8).await?;
+        } else if &input[inpos..inpos + 10] == b"NEG-CLOSE\"" {
+            self.neg_close(msg, inpos + 10).await?;
         } else {
             log::warn!(target: "Client", "{}: Received unhandled text message: {}", self.peer, msg);
             let reply = NostrReply::Notice("Command unrecognized".to_owned());
@@ -435,6 +443,233 @@ impl WebSocketService {
 
         Ok(())
     }
+
+    pub async fn neg_open(&mut self, msg: &str, mut inpos: usize) -> Result<(), Error> {
+        let input = msg.as_bytes();
+
+        // ["NEG-OPEN", "<subid>", "<filter>", "<hex-message>"]
+
+        eat_whitespace(input, &mut inpos);
+        verify_char(input, b',', &mut inpos)?;
+        eat_whitespace(input, &mut inpos);
+
+        let mut outpos = 0;
+
+        // Read the subid into the session buffer
+        let subid = {
+            verify_char(input, b'"', &mut inpos)?;
+            let (inlen, outlen) = json_unescape(&input[inpos..], &mut self.buffer[outpos..])?;
+            inpos += inlen;
+            let subid = unsafe {
+                String::from_utf8_unchecked(self.buffer[outpos..outpos + outlen].to_owned())
+            };
+            outpos += outlen;
+            verify_char(input, b'"', &mut inpos)?; // FIXME: json_unescape should eat the closing quote
+            subid
+        };
+
+        // Read the filter into the session buffer
+        let filter = {
+            eat_whitespace(input, &mut inpos);
+            verify_char(input, b',', &mut inpos)?;
+            // whitespace after the comma is handled within Filter::from_json
+            let (incount, outcount, filter) =
+                Filter::from_json(&input[inpos..], &mut self.buffer[outpos..])?;
+            inpos += incount;
+            outpos += outcount;
+            filter.to_owned()
+        };
+
+        // Read the negentropy message
+        let incoming_msg = {
+            eat_whitespace(input, &mut inpos);
+            verify_char(input, b',', &mut inpos)?;
+            eat_whitespace(input, &mut inpos);
+            verify_char(input, b'"', &mut inpos)?;
+            let (inlen, outlen) = json_unescape(&input[inpos..], &mut self.buffer[outpos..])?;
+            inpos += inlen;
+            verify_char(input, b'"', &mut inpos)?;
+            let mut msg = vec![0; outlen / 2];
+            read_hex!(&self.buffer[outpos..outpos + outlen], &mut msg, outlen / 2)?;
+            //outpos += outlen;
+            msg
+        };
+
+        // NEG-ERR if the message was empty
+        if incoming_msg.is_empty() {
+            let reply = NostrReply::NegErr(&subid, "Empty negentropy message".to_owned());
+            self.send(Message::text(reply.as_json())).await?;
+            return Ok(());
+        }
+
+        // If the version is too high, respond with our version number
+        if incoming_msg[0] != 0x61 {
+            let reply = NostrReply::NegMsg(&subid, vec![0x61]);
+            self.send(Message::text(reply.as_json())).await?;
+            return Ok(());
+        }
+
+        let user = self.user;
+        let authorized_user = authorized_user(&user);
+
+        // Find all matching events
+        let mut events: Vec<&Event> = Vec::new();
+        let screen = |event: &Event| {
+            let event_flags = event_flags(event, &user);
+            screen_outgoing_event(event, &event_flags, authorized_user)
+        };
+        let filter_events = {
+            let config = &*GLOBALS.config.read();
+            GLOBALS.store.get().unwrap().find_events(
+                &filter,
+                config.allow_scraping,
+                config.allow_scrape_if_limited_to,
+                config.allow_scrape_if_max_seconds,
+                screen,
+            )?
+        };
+        events.extend(filter_events);
+        events.sort_by(|a, b| {
+            a.created_at()
+                .cmp(&b.created_at())
+                .then(a.id().cmp(&b.id()))
+        });
+        events.dedup();
+
+        let mut nsv = NegentropyStorageVector::with_capacity(events.len());
+        for event in &events {
+            let id = negentropy::Id::from_slice(event.id().as_slice())?;
+            let time = event.created_at().as_u64();
+            nsv.insert(time, id)?;
+        }
+        nsv.seal()?;
+
+        // Save the matching events under the subscription Id
+        self.neg_subscriptions.insert(subid.clone(), nsv);
+
+        // Look it up again immediately
+        let Some(nsv) = self.neg_subscriptions.get(&subid) else {
+            return Err(ChorusError::General(
+                "NEG-OPEN inserted data is immediately missing!".to_owned(),
+            )
+            .into());
+        };
+
+        let mut neg = Negentropy::new(nsv, 1024 * 1024)?; // websocket frame size limit
+        match neg.reconcile(&Bytes::from(incoming_msg)) {
+            Ok(response) => {
+                let reply = NostrReply::NegMsg(&subid, response.as_bytes().to_owned());
+                self.send(Message::text(reply.as_json())).await?;
+            }
+            Err(e) => {
+                let reply = NostrReply::NegErr(&subid, format!("{e}"));
+                self.send(Message::text(reply.as_json())).await?;
+            }
+        }
+
+        Ok(())
+    }
+
+    pub async fn neg_msg(&mut self, msg: &str, mut inpos: usize) -> Result<(), Error> {
+        let input = msg.as_bytes();
+
+        // ["NEG-MSG", "<subid>", "<hex-message>"]
+        eat_whitespace(input, &mut inpos);
+        verify_char(input, b',', &mut inpos)?;
+        eat_whitespace(input, &mut inpos);
+
+        let mut outpos = 0;
+
+        // Read the subid into the session buffer
+        let subid = {
+            verify_char(input, b'"', &mut inpos)?;
+            let (inlen, outlen) = json_unescape(&input[inpos..], &mut self.buffer[outpos..])?;
+            inpos += inlen;
+            let subid = unsafe {
+                String::from_utf8_unchecked(self.buffer[outpos..outpos + outlen].to_owned())
+            };
+            outpos += outlen;
+            verify_char(input, b'"', &mut inpos)?; // FIXME: json_unescape should eat the closing quote
+            subid
+        };
+
+        // Read the negentropy message
+        let incoming_msg = {
+            eat_whitespace(input, &mut inpos);
+            verify_char(input, b',', &mut inpos)?;
+            eat_whitespace(input, &mut inpos);
+            verify_char(input, b'"', &mut inpos)?;
+            let (inlen, outlen) = json_unescape(&input[inpos..], &mut self.buffer[outpos..])?;
+            inpos += inlen;
+            verify_char(input, b'"', &mut inpos)?;
+            let mut msg = vec![0; outlen / 2];
+            read_hex!(&self.buffer[outpos..outpos + outlen], &mut msg, outlen / 2)?;
+            // outpos += outlen;
+            msg
+        };
+
+        // NEG-ERR if the message was empty
+        if incoming_msg.is_empty() {
+            let reply = NostrReply::NegErr(&subid, "Empty negentropy message".to_owned());
+            self.send(Message::text(reply.as_json())).await?;
+            return Ok(());
+        }
+
+        // If the version is too high, return an error (version negotiation should
+        // have already happened in NEG-OPEN)
+        if incoming_msg[0] != 0x61 {
+            let reply = NostrReply::NegErr(&subid, "Version mismatch".to_owned());
+            self.send(Message::text(reply.as_json())).await?;
+            return Ok(());
+        }
+
+        // Look up the events we have
+        let Some(nsv) = self.neg_subscriptions.get(&subid) else {
+            let reply = NostrReply::NegErr(&subid, "Subscription not found".to_owned());
+            self.send(Message::text(reply.as_json())).await?;
+            return Ok(());
+        };
+
+        let mut neg = Negentropy::new(nsv, 1024 * 1024)?; // websocket frame size limit
+        match neg.reconcile(&Bytes::from(incoming_msg)) {
+            Ok(response) => {
+                let reply = NostrReply::NegMsg(&subid, response.as_bytes().to_owned());
+                self.send(Message::text(reply.as_json())).await?;
+            }
+            Err(e) => {
+                let reply = NostrReply::NegErr(&subid, format!("{e}"));
+                self.send(Message::text(reply.as_json())).await?;
+            }
+        }
+
+        Ok(())
+    }
+
+    pub async fn neg_close(&mut self, msg: &str, mut inpos: usize) -> Result<(), Error> {
+        let input = msg.as_bytes();
+
+        // ["NEG-CLOSE", "<subid>"]
+
+        eat_whitespace(input, &mut inpos);
+        verify_char(input, b',', &mut inpos)?;
+        eat_whitespace(input, &mut inpos);
+
+        // Read the subid into the session buffer
+        let subid = {
+            verify_char(input, b'"', &mut inpos)?;
+            let (inlen, outlen) = json_unescape(&input[inpos..], &mut self.buffer)?;
+            inpos += inlen;
+            let subid = unsafe { String::from_utf8_unchecked(self.buffer[..outlen].to_owned()) };
+            verify_char(input, b'"', &mut inpos)?; // FIXME: json_unescape should eat the closing quote
+            subid
+        };
+
+        // Close the subscription
+        self.neg_subscriptions.remove(&subid);
+
+        // No need to reply to the client
+        Ok(())
+    }
 }
 
 async fn screen_incoming_event(
diff --git a/src/reply.rs b/src/reply.rs
index c3f3501..695d6a0 100644
--- a/src/reply.rs
+++ b/src/reply.rs
@@ -1,4 +1,4 @@
-use pocket_types::{Event, Hll8, Id};
+use pocket_types::{write_hex, Event, Hll8, Id};
 use std::fmt;
 
 #[derive(Debug, Clone, Copy)]
@@ -40,6 +40,8 @@ pub enum NostrReply<'a> {
     Closed(&'a str, NostrReplyPrefix, String),
     Notice(String),
     Count(&'a str, usize, Option<Hll8>),
+    NegErr(&'a str, String),
+    NegMsg(&'a str, Vec<u8>),
 }
 
 impl NostrReply<'_> {
@@ -61,6 +63,16 @@ impl NostrReply<'_> {
                     format!(r#"["COUNT","{subid}",{{"count":{c}}}]"#)
                 }
             }
+            NostrReply::NegErr(subid, reason) => {
+                format!(r#"["NEG-ERR","{subid}","{reason}"]"#)
+            }
+            NostrReply::NegMsg(subid, msg) => {
+                // write msg as hex
+                let mut buf: Vec<u8> = vec![0; msg.len() * 2];
+                write_hex!(msg, &mut buf, msg.len()).unwrap();
+                let msg_hex = unsafe { std::str::from_utf8_unchecked(&buf) };
+                format!(r#"["NEG-MSG","{subid}","{}"]"#, msg_hex)
+            }
         }
     }
 }