From 38b20e873ec2901d58fd4a484a996d3abe4d535a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tom=C3=A1s=20Gr=C3=BCner?=
 <47506558+MegaRedHand@users.noreply.github.com>
Date: Wed, 7 Jan 2026 15:03:26 -0300
Subject: [PATCH 01/10] feat: compute message ID

---
 Cargo.lock                |  1 +
 crates/net/p2p/Cargo.toml |  2 ++
 crates/net/p2p/src/lib.rs | 24 ++++++++++++++++++++++++
 3 files changed, 27 insertions(+)

diff --git a/Cargo.lock b/Cargo.lock
index ea611765..2558ed42 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1752,6 +1752,7 @@ dependencies = [
  "ethrex-rlp",
  "hex",
  "libp2p",
+ "sha2",
  "snap",
  "ssz_types",
  "tracing",
diff --git a/crates/net/p2p/Cargo.toml b/crates/net/p2p/Cargo.toml
index 369147e6..9a0e8ebd 100644
--- a/crates/net/p2p/Cargo.toml
+++ b/crates/net/p2p/Cargo.toml
@@ -32,5 +32,7 @@ ssz_types = "0.14.0"
 tree_hash = "0.12.0"
 tree_hash_derive = "0.12.0"
 
+sha2 = "0.10"
+
 [dev-dependencies]
 hex = "0.4"
diff --git a/crates/net/p2p/src/lib.rs b/crates/net/p2p/src/lib.rs
index bde9c565..360fc69b 100644
--- a/crates/net/p2p/src/lib.rs
+++ b/crates/net/p2p/src/lib.rs
@@ -12,6 +12,7 @@ use libp2p::{
     request_response::{self, Event, Message},
     swarm::{NetworkBehaviour, SwarmEvent},
 };
+use sha2::Digest;
 use tracing::{info, trace};
 
 use crate::messages::status::{STATUS_PROTOCOL_V1, Status};
@@ -35,12 +36,14 @@ pub async fn start_p2p(bootnodes: Vec<Bootnode>, listening_port: u16) {
         // seen_ttl_secs = seconds_per_slot * justification_lookback_slots * 2
         .duplicate_cache_time(Duration::from_secs(4 * 3 * 2))
         .validation_mode(ValidationMode::Anonymous)
+        .message_id_fn(compute_message_id)
         .build()
         .expect("invalid gossipsub config");
 
     // TODO: setup custom message ID function
     let gossipsub = libp2p::gossipsub::Behaviour::new(MessageAuthenticity::Anonymous, config)
         .expect("failed to initiate behaviour");
+
     let req_resp = request_response::Behaviour::new(
         vec![(
             StreamProtocol::new(STATUS_PROTOCOL_V1),
@@ -214,3 +217,24 @@ pub fn parse_validators_file(bootnodes_path: &str) -> Vec<Bootnode> {
     }
     bootnodes
 }
+
+fn compute_message_id(message: &gossipsub::Message) -> gossipsub::MessageId {
+    const MESSAGE_DOMAIN_INVALID_SNAPPY: [u8; 4] = [0x00, 0x00, 0x00, 0x00];
+    const MESSAGE_DOMAIN_VALID_SNAPPY: [u8; 4] = [0x01, 0x00, 0x00, 0x00];
+
+    let mut hasher = sha2::Sha256::new();
+    let decompressed = snap::raw::Decoder::new().decompress_vec(&message.data);
+
+    let (domain, data) = match decompressed.as_ref() {
+        Ok(decompressed_data) => (MESSAGE_DOMAIN_VALID_SNAPPY, decompressed_data),
+        Err(_) => (MESSAGE_DOMAIN_INVALID_SNAPPY, &message.data),
+    };
+    let topic = message.topic.as_str().as_bytes();
+    let topic_len = (topic.len() as u64).to_be_bytes();
+    hasher.update(&domain);
+    hasher.update(&topic_len);
+    hasher.update(topic);
+    hasher.update(data);
+    let hash = hasher.finalize();
+    gossipsub::MessageId(hash[..20].to_vec())
+}

From 0b65f75b195e3bbfc53786e80e8e0fe33b123940 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tom=C3=A1s=20Gr=C3=BCner?=
 <47506558+MegaRedHand@users.noreply.github.com>
Date: Wed, 7 Jan 2026 15:23:11 -0300
Subject: [PATCH 02/10] feat: subscribe to gossipsub topics

---
 crates/net/p2p/src/lib.rs | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/crates/net/p2p/src/lib.rs b/crates/net/p2p/src/lib.rs
index 360fc69b..1f1e0118 100644
--- a/crates/net/p2p/src/lib.rs
+++ b/crates/net/p2p/src/lib.rs
@@ -96,6 +96,14 @@ pub async fn start_p2p(bootnodes: Vec<Bootnode>, listening_port: u16) {
         .listen_on(addr)
         .expect("failed to bind gossipsub listening address");
 
+    let topic_kinds = ["block", "attestation"];
+    let network = "devnet0";
+    for topic_kind in topic_kinds {
+        let topic_str = format!("/leanconsensus/{network}/{topic_kind}/ssz_snappy");
+        let topic = gossipsub::IdentTopic::new(topic_str);
+        swarm.behaviour_mut().gossipsub.subscribe(&topic).unwrap();
+    }
+
     println!("P2P node started on port {listening_port}");
 
     event_loop(swarm).await;

From ec37ebfee340cbdcc40677f234707d27d0d615db Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tom=C3=A1s=20Gr=C3=BCner?=
 <47506558+MegaRedHand@users.noreply.github.com>
Date: Wed, 7 Jan 2026 18:27:56 -0300
Subject: [PATCH 03/10] feat: receive block and attestation gossip

---
 crates/net/p2p/src/lib.rs | 66 ++++++++++++++++++++++++++++-----------
 1 file changed, 47 insertions(+), 19 deletions(-)

diff --git a/crates/net/p2p/src/lib.rs b/crates/net/p2p/src/lib.rs
index 1f1e0118..55b73085 100644
--- a/crates/net/p2p/src/lib.rs
+++ b/crates/net/p2p/src/lib.rs
@@ -9,7 +9,7 @@ use libp2p::{
     gossipsub::{self, MessageAuthenticity, ValidationMode},
     identity::{PublicKey, secp256k1},
     multiaddr::Protocol,
-    request_response::{self, Event, Message},
+    request_response,
     swarm::{NetworkBehaviour, SwarmEvent},
 };
 use sha2::Digest;
@@ -17,6 +17,11 @@ use tracing::{info, trace};
 
 use crate::messages::status::{STATUS_PROTOCOL_V1, Status};
 
+/// Topic kind for block gossip
+const BLOCK_TOPIC_KIND: &str = "block";
+/// Topic kind for attestation gossip
+const ATTESTATION_TOPIC_KIND: &str = "attestation";
+
 mod messages;
 
 pub async fn start_p2p(bootnodes: Vec<Bootnode>, listening_port: u16) {
@@ -96,7 +101,7 @@ pub async fn start_p2p(bootnodes: Vec<Bootnode>, listening_port: u16) {
         .listen_on(addr)
         .expect("failed to bind gossipsub listening address");
 
-    let topic_kinds = ["block", "attestation"];
+    let topic_kinds = [BLOCK_TOPIC_KIND, ATTESTATION_TOPIC_KIND];
     let network = "devnet0";
     for topic_kind in topic_kinds {
         let topic_str = format!("/leanconsensus/{network}/{topic_kind}/ssz_snappy");
@@ -121,21 +126,16 @@ struct Behaviour {
 async fn event_loop(mut swarm: libp2p::Swarm<Behaviour>) {
     while let Some(event) = swarm.next().await {
         match event {
-            SwarmEvent::Behaviour(BehaviourEvent::ReqResp(message @ Event::Message { .. })) => {
+            SwarmEvent::Behaviour(BehaviourEvent::ReqResp(
+                message @ request_response::Event::Message { .. },
+            )) => {
                 handle_req_resp_message(&mut swarm, message).await;
             }
-            // SwarmEvent::Behaviour(BehaviourEvent::ReqResp(Event::Message {
-            //     peer,
-            //     connection_id,
-            //     message:
-            //         Message::Request {
-            //             request_id,
-            //             request,
-            //             channel,
-            //         },
-            // })) => {
-            //     info!(finalized_slot=%request.finalized.slot, head_slot=%request.head.slot, "Received status request from peer {peer}");
-            // }
+            SwarmEvent::Behaviour(BehaviourEvent::Gossipsub(
+                message @ gossipsub::Event::Message { .. },
+            )) => {
+                handle_gossipsub_message(&mut swarm, message).await;
+            }
             _ => {
                 trace!(?event, "Ignored swarm event");
             }
@@ -145,9 +145,9 @@ async fn event_loop(mut swarm: libp2p::Swarm<Behaviour>) {
 
 async fn handle_req_resp_message(
     swarm: &mut libp2p::Swarm<Behaviour>,
-    event: Event<Status, Status>,
+    event: request_response::Event<Status, Status>,
 ) {
-    let Event::Message {
+    let request_response::Event::Message {
         peer,
         connection_id: _,
         message,
@@ -156,7 +156,7 @@ async fn handle_req_resp_message(
         unreachable!("we already matched on event_loop");
     };
     match message {
-        Message::Request {
+        request_response::Message::Request {
             request_id: _,
             request,
             channel,
@@ -169,7 +169,7 @@ async fn handle_req_resp_message(
                 .unwrap();
             swarm.behaviour_mut().req_resp.send_request(&peer, request);
         }
-        Message::Response {
+        request_response::Message::Response {
             request_id: _,
             response,
         } => {
@@ -178,6 +178,34 @@ async fn handle_req_resp_message(
     }
 }
 
+async fn handle_gossipsub_message(swarm: &mut libp2p::Swarm<Behaviour>, event: gossipsub::Event) {
+    let gossipsub::Event::Message {
+        propagation_source: _,
+        message_id: _,
+        message,
+    } = event
+    else {
+        unreachable!("we already matched on event_loop");
+    };
+    match message.topic.as_str().split("/").nth(2) {
+        Some(BLOCK_TOPIC_KIND) => {
+            info!(
+                "Received block gossip message of size {} bytes",
+                message.data.len()
+            );
+        }
+        Some(ATTESTATION_TOPIC_KIND) => {
+            info!(
+                "Received attestation gossip message of size {} bytes",
+                message.data.len()
+            );
+        }
+        _ => {
+            trace!("Received message on unknown topic: {}", message.topic);
+        }
+    }
+}
+
 pub struct Bootnode {
     ip: IpAddr,
     quic_port: u16,

From 0481410199bd7ff273c0311d964b2a5da262951a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tom=C3=A1s=20Gr=C3=BCner?=
 <47506558+MegaRedHand@users.noreply.github.com>
Date: Wed, 7 Jan 2026 18:43:39 -0300
Subject: [PATCH 04/10] chore: move gossipsub handler to own module

---
 crates/net/p2p/src/gossipsub.rs | 36 ++++++++++++++++++++++
 crates/net/p2p/src/lib.rs       | 53 ++++++++-------------------------
 2 files changed, 48 insertions(+), 41 deletions(-)
 create mode 100644 crates/net/p2p/src/gossipsub.rs

diff --git a/crates/net/p2p/src/gossipsub.rs b/crates/net/p2p/src/gossipsub.rs
new file mode 100644
index 00000000..9426e6a2
--- /dev/null
+++ b/crates/net/p2p/src/gossipsub.rs
@@ -0,0 +1,36 @@
+use crate::Behaviour;
+use libp2p::gossipsub::Event;
+use tracing::{info, trace};
+
+/// Topic kind for block gossip
+pub const BLOCK_TOPIC_KIND: &str = "block";
+/// Topic kind for attestation gossip
+pub const ATTESTATION_TOPIC_KIND: &str = "attestation";
+
+pub async fn handle_gossipsub_message(swarm: &mut libp2p::Swarm<Behaviour>, event: Event) {
+    let Event::Message {
+        propagation_source: _,
+        message_id: _,
+        message,
+    } = event
+    else {
+        unreachable!("we already matched on event_loop");
+    };
+    match message.topic.as_str().split("/").nth(2) {
+        Some(BLOCK_TOPIC_KIND) => {
+            info!(
+                "Received block gossip message of size {} bytes",
+                message.data.len()
+            );
+        }
+        Some(ATTESTATION_TOPIC_KIND) => {
+            info!(
+                "Received attestation gossip message of size {} bytes",
+                message.data.len()
+            );
+        }
+        _ => {
+            trace!("Received message on unknown topic: {}", message.topic);
+        }
+    }
+}
diff --git a/crates/net/p2p/src/lib.rs b/crates/net/p2p/src/lib.rs
index 55b73085..b4441ace 100644
--- a/crates/net/p2p/src/lib.rs
+++ b/crates/net/p2p/src/lib.rs
@@ -6,7 +6,7 @@ use ethrex_rlp::decode::RLPDecode;
 use libp2p::{
     Multiaddr, PeerId, StreamProtocol,
     futures::StreamExt,
-    gossipsub::{self, MessageAuthenticity, ValidationMode},
+    gossipsub::{MessageAuthenticity, ValidationMode},
     identity::{PublicKey, secp256k1},
     multiaddr::Protocol,
     request_response,
@@ -15,13 +15,12 @@ use libp2p::{
 use sha2::Digest;
 use tracing::{info, trace};
 
-use crate::messages::status::{STATUS_PROTOCOL_V1, Status};
-
-/// Topic kind for block gossip
-const BLOCK_TOPIC_KIND: &str = "block";
-/// Topic kind for attestation gossip
-const ATTESTATION_TOPIC_KIND: &str = "attestation";
+use crate::{
+    gossipsub::{ATTESTATION_TOPIC_KIND, BLOCK_TOPIC_KIND},
+    messages::status::{STATUS_PROTOCOL_V1, Status},
+};
 
+mod gossipsub;
 mod messages;
 
 pub async fn start_p2p(bootnodes: Vec<Bootnode>, listening_port: u16) {
@@ -105,7 +104,7 @@ pub async fn start_p2p(bootnodes: Vec<Bootnode>, listening_port: u16) {
     let network = "devnet0";
     for topic_kind in topic_kinds {
         let topic_str = format!("/leanconsensus/{network}/{topic_kind}/ssz_snappy");
-        let topic = gossipsub::IdentTopic::new(topic_str);
+        let topic = libp2p::gossipsub::IdentTopic::new(topic_str);
         swarm.behaviour_mut().gossipsub.subscribe(&topic).unwrap();
     }
 
@@ -117,7 +116,7 @@ pub async fn start_p2p(bootnodes: Vec<Bootnode>, listening_port: u16) {
 /// [libp2p Behaviour](libp2p::swarm::NetworkBehaviour) combining Gossipsub and Request-Response Behaviours
 #[derive(NetworkBehaviour)]
 struct Behaviour {
-    gossipsub: gossipsub::Behaviour,
+    gossipsub: libp2p::gossipsub::Behaviour,
     req_resp: request_response::Behaviour<messages::status::StatusCodec>,
 }
 
@@ -132,9 +131,9 @@ async fn event_loop(mut swarm: libp2p::Swarm<Behaviour>) {
                 handle_req_resp_message(&mut swarm, message).await;
             }
             SwarmEvent::Behaviour(BehaviourEvent::Gossipsub(
-                message @ gossipsub::Event::Message { .. },
+                message @ libp2p::gossipsub::Event::Message { .. },
             )) => {
-                handle_gossipsub_message(&mut swarm, message).await;
+                gossipsub::handle_gossipsub_message(&mut swarm, message).await;
             }
             _ => {
                 trace!(?event, "Ignored swarm event");
@@ -178,34 +177,6 @@ async fn handle_req_resp_message(
     }
 }
 
-async fn handle_gossipsub_message(swarm: &mut libp2p::Swarm<Behaviour>, event: gossipsub::Event) {
-    let gossipsub::Event::Message {
-        propagation_source: _,
-        message_id: _,
-        message,
-    } = event
-    else {
-        unreachable!("we already matched on event_loop");
-    };
-    match message.topic.as_str().split("/").nth(2) {
-        Some(BLOCK_TOPIC_KIND) => {
-            info!(
-                "Received block gossip message of size {} bytes",
-                message.data.len()
-            );
-        }
-        Some(ATTESTATION_TOPIC_KIND) => {
-            info!(
-                "Received attestation gossip message of size {} bytes",
-                message.data.len()
-            );
-        }
-        _ => {
-            trace!("Received message on unknown topic: {}", message.topic);
-        }
-    }
-}
-
 pub struct Bootnode {
     ip: IpAddr,
     quic_port: u16,
@@ -254,7 +225,7 @@ pub fn parse_validators_file(bootnodes_path: &str) -> Vec<Bootnode> {
     bootnodes
 }
 
-fn compute_message_id(message: &gossipsub::Message) -> gossipsub::MessageId {
+fn compute_message_id(message: &libp2p::gossipsub::Message) -> libp2p::gossipsub::MessageId {
     const MESSAGE_DOMAIN_INVALID_SNAPPY: [u8; 4] = [0x00, 0x00, 0x00, 0x00];
     const MESSAGE_DOMAIN_VALID_SNAPPY: [u8; 4] = [0x01, 0x00, 0x00, 0x00];
 
@@ -272,5 +243,5 @@ fn compute_message_id(message: &gossipsub::Message) -> gossipsub::MessageId {
     hasher.update(topic);
     hasher.update(data);
     let hash = hasher.finalize();
-    gossipsub::MessageId(hash[..20].to_vec())
+    libp2p::gossipsub::MessageId(hash[..20].to_vec())
 }

From d1f618713aceb4dffc15d3ab7088ddf8d3210f25 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tom=C3=A1s=20Gr=C3=BCner?=
 <47506558+MegaRedHand@users.noreply.github.com>
Date: Wed, 7 Jan 2026 18:57:16 -0300
Subject: [PATCH 05/10] test: add test deserializing a block

---
 crates/net/p2p/src/gossipsub.rs | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/crates/net/p2p/src/gossipsub.rs b/crates/net/p2p/src/gossipsub.rs
index 9426e6a2..07fedffb 100644
--- a/crates/net/p2p/src/gossipsub.rs
+++ b/crates/net/p2p/src/gossipsub.rs
@@ -16,7 +16,7 @@ pub async fn handle_gossipsub_message(swarm: &mut libp2p::Swarm<Behaviour>, even
     else {
         unreachable!("we already matched on event_loop");
     };
-    match message.topic.as_str().split("/").nth(2) {
+    match message.topic.as_str().split("/").nth(3) {
         Some(BLOCK_TOPIC_KIND) => {
             info!(
                 "Received block gossip message of size {} bytes",
@@ -34,3 +34,18 @@ pub async fn handle_gossipsub_message(swarm: &mut libp2p::Swarm<Behaviour>, even
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn deserialize_gossipsub_block_message() {
+        let hex_data = "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+        // Add tests for gossipsub message handling here
+        let data = hex::decode(hex_data).unwrap();
+        let size = snap::raw::decompress_len(&data).unwrap();
+        let mut buf = vec![0; size];
+        let mut decoder = snap::raw::Decoder::new();
+        decoder.decompress(&data, &mut buf).unwrap();
+        assert!(!buf.is_empty());
+    }
+}

From edd4f787f18452bbbf3d556f64b57192d37ae6ac Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tom=C3=A1s=20Gr=C3=BCner?=
 <47506558+MegaRedHand@users.noreply.github.com>
Date: Wed, 7 Jan 2026 19:15:08 -0300
Subject: [PATCH 06/10] feat: add block gossip types

---
 crates/common/types/src/attestation.rs | 31 ++++++++++++
 crates/common/types/src/block.rs       | 69 ++++++++++++++++++++++++--
 crates/common/types/src/lib.rs         |  1 +
 crates/common/types/src/state.rs       | 10 ++--
 4 files changed, 103 insertions(+), 8 deletions(-)
 create mode 100644 crates/common/types/src/attestation.rs

diff --git a/crates/common/types/src/attestation.rs b/crates/common/types/src/attestation.rs
new file mode 100644
index 00000000..e6d377f8
--- /dev/null
+++ b/crates/common/types/src/attestation.rs
@@ -0,0 +1,31 @@
+use ssz_types::typenum::N4096;
+
+use crate::state::Checkpoint;
+
+/// Validator specific attestation wrapping shared attestation data.
+pub struct Attestation {
+    /// The index of the validator making the attestation.
+    pub validator_id: u64,
+
+    /// The attestation data produced by the validator.
+    pub data: AttestationData,
+}
+
+/// Attestation content describing the validator's observed chain view.
+pub struct AttestationData {
+    /// The slot for which the attestation is made.
+    pub slot: u64,
+
+    /// The checkpoint representing the head block as observed by the validator.
+    pub head: Checkpoint,
+
+    /// The checkpoint representing the target block as observed by the validator.
+    pub target: Checkpoint,
+
+    /// The checkpoint representing the source block as observed by the validator.
+    pub source: Checkpoint,
+}
+
+/// List of validator attestations included in a block.
+/// Size limited to [`crate::state::VALIDATOR_REGISTRY_LIMIT`].
+pub type Attestations = ssz_types::VariableList<Attestation, N4096>;
diff --git a/crates/common/types/src/block.rs b/crates/common/types/src/block.rs
index bd29c673..30391870 100644
--- a/crates/common/types/src/block.rs
+++ b/crates/common/types/src/block.rs
@@ -1,6 +1,43 @@
-use crate::primitives::H256;
+use ssz_types::typenum::N4096;
 
-use crate::state::Slot;
+use crate::{
+    attestation::{Attestation, Attestations},
+    primitives::H256,
+};
+
+/// Envelope carrying a block, an attestation from proposer, and aggregated signatures.
+pub struct SignedBlockWithAttestation {
+    /// The block plus an attestation from proposer being signed.
+    pub message: BlockWithAttestation,
+
+    /// Aggregated signature payload for the block.
+    ///
+    /// Signatures remain in attestation order followed by the proposer signature
+    /// over entire message. For devnet 1, however the proposer signature is just
+    /// over message.proposer_attestation since leanVM is not yet performant enough
+    /// to aggregate signatures with sufficient throughput.
+    ///
+    /// Eventually this field will be replaced by a SNARK (which represents the
+    /// aggregation of all signatures).
+    pub signature: BlockSignatures,
+}
+
+/// Aggregated signature list included alongside the block.
+/// Size limited to [`crate::state::VALIDATOR_REGISTRY_LIMIT`].
+pub type BlockSignatures = ssz_types::VariableList<
+    // TODO: change to Signature type when available
+    u64,
+    N4096,
+>;
+
+/// Bundle containing a block and the proposer's attestation.
+pub struct BlockWithAttestation {
+    /// The proposed block message.
+    pub block: Block,
+
+    /// The proposer's attestation corresponding to this block.
+    pub proposer_attestation: Attestation,
+}
 
 /// The header of a block, containing metadata.
 ///
@@ -13,7 +50,7 @@ use crate::state::Slot;
 #[derive(Debug)]
 pub struct BlockHeader {
     /// The slot in which the block was proposed
-    pub slot: Slot,
+    pub slot: u64,
     /// The index of the validator that proposed the block
     pub proposer_index: u64,
     /// The root of the parent block
@@ -23,3 +60,29 @@ pub struct BlockHeader {
     /// The root of the block body
     pub body_root: H256,
 }
+
+/// A complete block including header and body.
+pub struct Block {
+    /// The slot in which the block was proposed.
+    pub slot: u64,
+    /// The index of the validator that proposed the block.
+    pub proposer_index: u64,
+    /// The root of the parent block.
+    pub parent_root: H256,
+    /// The root of the state after applying transactions in this block.
+    pub state_root: H256,
+    /// The block's payload.
+    pub body: BlockBody,
+}
+
+/// The body of a block, containing payload data.
+///
+/// Currently, the main operation is voting. Validators submit attestations which are
+/// packaged into blocks.
+pub struct BlockBody {
+    /// Plain validator attestations carried in the block body.
+    ///
+    /// Individual signatures live in the aggregated block signature list, so
+    /// these entries contain only attestation data without per-attestation signatures.
+    pub attestations: Attestations,
+}
diff --git a/crates/common/types/src/lib.rs b/crates/common/types/src/lib.rs
index c7c712e5..f6637042 100644
--- a/crates/common/types/src/lib.rs
+++ b/crates/common/types/src/lib.rs
@@ -1,3 +1,4 @@
+pub mod attestation;
 pub mod block;
 pub mod genesis;
 pub mod primitives;
diff --git a/crates/common/types/src/state.rs b/crates/common/types/src/state.rs
index 1e8869f9..234cf0f3 100644
--- a/crates/common/types/src/state.rs
+++ b/crates/common/types/src/state.rs
@@ -4,8 +4,8 @@ use tree_hash_derive::TreeHash;
 
 use crate::{block::BlockHeader, genesis::Genesis, primitives::H256};
 
-#[derive(Debug)]
-pub struct Slot(u64);
+/// The maximum number of validators that can be in the registry.
+pub const VALIDATOR_REGISTRY_LIMIT: u64 = 4096; // 2 ** 12
 
 /// The main consensus state object
 #[derive(Debug)]
@@ -13,7 +13,7 @@ pub struct State {
     /// The chain's configuration parameters
     config: NetworkConfig,
     /// The current slot number
-    slot: Slot,
+    slot: u64,
     /// The header of the most recent block
     latest_block_header: BlockHeader,
     /// The latest justified checkpoint
@@ -36,9 +36,9 @@ impl State {
     pub fn from_genesis(genesis: &Genesis) -> Self {
         State {
             config: genesis.config.clone(),
-            slot: Slot(0),
+            slot: 0,
             latest_block_header: BlockHeader {
-                slot: Slot(0),
+                slot: 0,
                 proposer_index: 0,
                 parent_root: H256::ZERO,
                 state_root: H256::ZERO,

From d2d2a0b5ec87b8d89103458255fc1e79b78eec46 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tom=C3=A1s=20Gr=C3=BCner?=
 <47506558+MegaRedHand@users.noreply.github.com>
Date: Thu, 8 Jan 2026 11:41:10 -0300
Subject: [PATCH 07/10] feat: implement SSZ for types

---
 Cargo.lock                             | 266 ++++++++++++++++++++++---
 Cargo.toml                             |   3 +
 crates/common/types/Cargo.toml         |   2 +
 crates/common/types/src/attestation.rs |   8 +-
 crates/common/types/src/block.rs       |  27 ++-
 crates/common/types/src/lib.rs         |   1 +
 crates/common/types/src/signature.rs   |   7 +
 7 files changed, 279 insertions(+), 35 deletions(-)
 create mode 100644 crates/common/types/src/signature.rs

diff --git a/Cargo.lock b/Cargo.lock
index 2558ed42..39432a69 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1336,6 +1336,20 @@ dependencies = [
  "syn 2.0.111",
 ]
 
+[[package]]
+name = "dashmap"
+version = "6.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5041cc499144891f3790297212f32a74fb938e5136a14943f338ef9e0ae276cf"
+dependencies = [
+ "cfg-if 1.0.4",
+ "crossbeam-utils 0.8.21",
+ "hashbrown 0.14.5",
+ "lock_api",
+ "once_cell",
+ "parking_lot_core",
+]
+
 [[package]]
 name = "data-encoding"
 version = "2.9.0"
@@ -1779,6 +1793,7 @@ dependencies = [
  "ethereum-types",
  "ethereum_ssz",
  "ethereum_ssz_derive",
+ "leansig",
  "serde",
  "ssz_types",
  "thiserror 2.0.17",
@@ -2996,7 +3011,7 @@ dependencies = [
  "serde_arrays",
  "sha2",
  "sp1_bls12_381",
- "spin",
+ "spin 0.9.8",
 ]
 
 [[package]]
@@ -3020,6 +3035,26 @@ version = "1.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "bbd2bcb4c963f2ddae06a2efc7e9f3591312473c50c6685e1f298068316e66fe"
 
+[[package]]
+name = "leansig"
+version = "0.1.0"
+source = "git+https://github.com/leanEthereum/leansig.git?rev=ae12a5feb25d917c42b6466444ebd56ec115a629#ae12a5feb25d917c42b6466444ebd56ec115a629"
+dependencies = [
+ "dashmap",
+ "ethereum_ssz",
+ "num-bigint 0.4.6",
+ "num-traits",
+ "p3-baby-bear 0.4.1",
+ "p3-field 0.4.1",
+ "p3-koala-bear",
+ "p3-symmetric 0.4.1",
+ "rand 0.9.2",
+ "rayon",
+ "serde",
+ "sha3",
+ "thiserror 2.0.17",
+]
+
 [[package]]
 name = "libc"
 version = "0.2.178"
@@ -4228,24 +4263,65 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7521838ecab2ddf4f7bc4ceebad06ec02414729598485c1ada516c39900820e8"
 dependencies = [
  "num-bigint 0.4.6",
- "p3-field",
- "p3-mds",
- "p3-poseidon2",
- "p3-symmetric",
+ "p3-field 0.2.3-succinct",
+ "p3-mds 0.2.3-succinct",
+ "p3-poseidon2 0.2.3-succinct",
+ "p3-symmetric 0.2.3-succinct",
  "rand 0.8.5",
  "serde",
 ]
 
+[[package]]
+name = "p3-baby-bear"
+version = "0.4.1"
+source = "git+https://github.com/Plonky3/Plonky3.git?rev=d421e32#d421e32d3821174ae1f7e528d4bb92b7b18ab295"
+dependencies = [
+ "p3-challenger",
+ "p3-field 0.4.1",
+ "p3-mds 0.4.1",
+ "p3-monty-31",
+ "p3-poseidon2 0.4.1",
+ "p3-symmetric 0.4.1",
+ "rand 0.9.2",
+]
+
+[[package]]
+name = "p3-challenger"
+version = "0.4.1"
+source = "git+https://github.com/Plonky3/Plonky3.git?rev=d421e32#d421e32d3821174ae1f7e528d4bb92b7b18ab295"
+dependencies = [
+ "p3-field 0.4.1",
+ "p3-maybe-rayon 0.4.1",
+ "p3-monty-31",
+ "p3-symmetric 0.4.1",
+ "p3-util 0.4.1",
+ "tracing",
+]
+
 [[package]]
 name = "p3-dft"
 version = "0.2.3-succinct"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "46414daedd796f1eefcdc1811c0484e4bced5729486b6eaba9521c572c76761a"
 dependencies = [
- "p3-field",
- "p3-matrix",
- "p3-maybe-rayon",
- "p3-util",
+ "p3-field 0.2.3-succinct",
+ "p3-matrix 0.2.3-succinct",
+ "p3-maybe-rayon 0.2.3-succinct",
+ "p3-util 0.2.3-succinct",
+ "tracing",
+]
+
+[[package]]
+name = "p3-dft"
+version = "0.4.1"
+source = "git+https://github.com/Plonky3/Plonky3.git?rev=d421e32#d421e32d3821174ae1f7e528d4bb92b7b18ab295"
+dependencies = [
+ "itertools 0.14.0",
+ "p3-field 0.4.1",
+ "p3-matrix 0.4.1",
+ "p3-maybe-rayon 0.4.1",
+ "p3-util 0.4.1",
+ "spin 0.10.0",
  "tracing",
 ]
 
@@ -4258,11 +4334,39 @@ dependencies = [
  "itertools 0.12.1",
  "num-bigint 0.4.6",
  "num-traits",
- "p3-util",
+ "p3-util 0.2.3-succinct",
  "rand 0.8.5",
  "serde",
 ]
 
+[[package]]
+name = "p3-field"
+version = "0.4.1"
+source = "git+https://github.com/Plonky3/Plonky3.git?rev=d421e32#d421e32d3821174ae1f7e528d4bb92b7b18ab295"
+dependencies = [
+ "itertools 0.14.0",
+ "num-bigint 0.4.6",
+ "p3-maybe-rayon 0.4.1",
+ "p3-util 0.4.1",
+ "paste",
+ "rand 0.9.2",
+ "serde",
+ "tracing",
+]
+
+[[package]]
+name = "p3-koala-bear"
+version = "0.4.1"
+source = "git+https://github.com/Plonky3/Plonky3.git?rev=d421e32#d421e32d3821174ae1f7e528d4bb92b7b18ab295"
+dependencies = [
+ "p3-challenger",
+ "p3-field 0.4.1",
+ "p3-monty-31",
+ "p3-poseidon2 0.4.1",
+ "p3-symmetric 0.4.1",
+ "rand 0.9.2",
+]
+
 [[package]]
 name = "p3-matrix"
 version = "0.2.3-succinct"
@@ -4270,20 +4374,40 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3e4de3f373589477cb735ea58e125898ed20935e03664b4614c7fac258b3c42f"
 dependencies = [
  "itertools 0.12.1",
- "p3-field",
- "p3-maybe-rayon",
- "p3-util",
+ "p3-field 0.2.3-succinct",
+ "p3-maybe-rayon 0.2.3-succinct",
+ "p3-util 0.2.3-succinct",
  "rand 0.8.5",
  "serde",
  "tracing",
 ]
 
+[[package]]
+name = "p3-matrix"
+version = "0.4.1"
+source = "git+https://github.com/Plonky3/Plonky3.git?rev=d421e32#d421e32d3821174ae1f7e528d4bb92b7b18ab295"
+dependencies = [
+ "itertools 0.14.0",
+ "p3-field 0.4.1",
+ "p3-maybe-rayon 0.4.1",
+ "p3-util 0.4.1",
+ "rand 0.9.2",
+ "serde",
+ "tracing",
+ "transpose",
+]
+
 [[package]]
 name = "p3-maybe-rayon"
 version = "0.2.3-succinct"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c3968ad1160310296eb04f91a5f4edfa38fe1d6b2b8cd6b5c64e6f9b7370979e"
 
+[[package]]
+name = "p3-maybe-rayon"
+version = "0.4.1"
+source = "git+https://github.com/Plonky3/Plonky3.git?rev=d421e32#d421e32d3821174ae1f7e528d4bb92b7b18ab295"
+
 [[package]]
 name = "p3-mds"
 version = "0.2.3-succinct"
@@ -4291,14 +4415,49 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2356b1ed0add6d5dfbf7a338ce534a6fde827374394a52cec16a0840af6e97c9"
 dependencies = [
  "itertools 0.12.1",
- "p3-dft",
- "p3-field",
- "p3-matrix",
- "p3-symmetric",
- "p3-util",
+ "p3-dft 0.2.3-succinct",
+ "p3-field 0.2.3-succinct",
+ "p3-matrix 0.2.3-succinct",
+ "p3-symmetric 0.2.3-succinct",
+ "p3-util 0.2.3-succinct",
  "rand 0.8.5",
 ]
 
+[[package]]
+name = "p3-mds"
+version = "0.4.1"
+source = "git+https://github.com/Plonky3/Plonky3.git?rev=d421e32#d421e32d3821174ae1f7e528d4bb92b7b18ab295"
+dependencies = [
+ "p3-dft 0.4.1",
+ "p3-field 0.4.1",
+ "p3-symmetric 0.4.1",
+ "p3-util 0.4.1",
+ "rand 0.9.2",
+]
+
+[[package]]
+name = "p3-monty-31"
+version = "0.4.1"
+source = "git+https://github.com/Plonky3/Plonky3.git?rev=d421e32#d421e32d3821174ae1f7e528d4bb92b7b18ab295"
+dependencies = [
+ "itertools 0.14.0",
+ "num-bigint 0.4.6",
+ "p3-dft 0.4.1",
+ "p3-field 0.4.1",
+ "p3-matrix 0.4.1",
+ "p3-maybe-rayon 0.4.1",
+ "p3-mds 0.4.1",
+ "p3-poseidon2 0.4.1",
+ "p3-symmetric 0.4.1",
+ "p3-util 0.4.1",
+ "paste",
+ "rand 0.9.2",
+ "serde",
+ "spin 0.10.0",
+ "tracing",
+ "transpose",
+]
+
 [[package]]
 name = "p3-poseidon2"
 version = "0.2.3-succinct"
@@ -4306,13 +4465,25 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7da1eec7e1b6900581bedd95e76e1ef4975608dd55be9872c9d257a8a9651c3a"
 dependencies = [
  "gcd",
- "p3-field",
- "p3-mds",
- "p3-symmetric",
+ "p3-field 0.2.3-succinct",
+ "p3-mds 0.2.3-succinct",
+ "p3-symmetric 0.2.3-succinct",
  "rand 0.8.5",
  "serde",
 ]
 
+[[package]]
+name = "p3-poseidon2"
+version = "0.4.1"
+source = "git+https://github.com/Plonky3/Plonky3.git?rev=d421e32#d421e32d3821174ae1f7e528d4bb92b7b18ab295"
+dependencies = [
+ "p3-field 0.4.1",
+ "p3-mds 0.4.1",
+ "p3-symmetric 0.4.1",
+ "p3-util 0.4.1",
+ "rand 0.9.2",
+]
+
 [[package]]
 name = "p3-symmetric"
 version = "0.2.3-succinct"
@@ -4320,7 +4491,17 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "edb439bea1d822623b41ff4b51e3309e80d13cadf8b86d16ffd5e6efb9fdc360"
 dependencies = [
  "itertools 0.12.1",
- "p3-field",
+ "p3-field 0.2.3-succinct",
+ "serde",
+]
+
+[[package]]
+name = "p3-symmetric"
+version = "0.4.1"
+source = "git+https://github.com/Plonky3/Plonky3.git?rev=d421e32#d421e32d3821174ae1f7e528d4bb92b7b18ab295"
+dependencies = [
+ "itertools 0.14.0",
+ "p3-field 0.4.1",
  "serde",
 ]
 
@@ -4333,6 +4514,14 @@ dependencies = [
  "serde",
 ]
 
+[[package]]
+name = "p3-util"
+version = "0.4.1"
+source = "git+https://github.com/Plonky3/Plonky3.git?rev=d421e32#d421e32d3821174ae1f7e528d4bb92b7b18ab295"
+dependencies = [
+ "serde",
+]
+
 [[package]]
 name = "pairing"
 version = "0.23.0"
@@ -5617,10 +5806,10 @@ dependencies = [
  "hex",
  "lazy_static",
  "num-bigint 0.4.6",
- "p3-baby-bear",
- "p3-field",
- "p3-poseidon2",
- "p3-symmetric",
+ "p3-baby-bear 0.2.3-succinct",
+ "p3-field 0.2.3-succinct",
+ "p3-poseidon2 0.2.3-succinct",
+ "p3-symmetric 0.2.3-succinct",
  "serde",
  "sha2",
 ]
@@ -5673,6 +5862,15 @@ version = "0.9.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6980e8d7511241f8acf4aebddbb1ff938df5eebe98691418c4468d0b72a96a67"
 
+[[package]]
+name = "spin"
+version = "0.10.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d5fe4ccb98d9c292d56fec89a5e07da7fc4cf0dc11e156b41793132775d3e591"
+dependencies = [
+ "lock_api",
+]
+
 [[package]]
 name = "spki"
 version = "0.7.3"
@@ -5711,6 +5909,12 @@ version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a2eb9349b6444b326872e140eb1cf5e7c522154d69e7a0ffb0fb81c06b37543f"
 
+[[package]]
+name = "strength_reduce"
+version = "0.2.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fe895eb47f22e2ddd4dabc02bce419d2e643c8e3b585c78158b349195bc24d82"
+
 [[package]]
 name = "strsim"
 version = "0.11.1"
@@ -6122,6 +6326,16 @@ dependencies = [
  "tracing-log",
 ]
 
+[[package]]
+name = "transpose"
+version = "0.2.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1ad61aed86bc3faea4300c7aee358b4c6d0c8d6ccc36524c96e4c92ccf26e77e"
+dependencies = [
+ "num-integer",
+ "strength_reduce",
+]
+
 [[package]]
 name = "tree_hash"
 version = "0.12.0"
diff --git a/Cargo.toml b/Cargo.toml
index 60c86dc5..7e206963 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -44,6 +44,9 @@ clap = { version = "4.3", features = ["derive", "env"] }
 # TODO: switch to ethrex implementation when available
 ethereum-types = { version = "0.15.1", features = ["serialize"] }
 
+# XMSS signatures
+leansig = { git = "https://github.com/leanEthereum/leansig.git", rev = "ae12a5feb25d917c42b6466444ebd56ec115a629" }
+
 # SSZ deps
 # TODO: roll up our own implementation
 ethereum_ssz_derive = "0.8.3"
diff --git a/crates/common/types/Cargo.toml b/crates/common/types/Cargo.toml
index 8391b0c5..556d4395 100644
--- a/crates/common/types/Cargo.toml
+++ b/crates/common/types/Cargo.toml
@@ -14,6 +14,8 @@ thiserror.workspace = true
 serde.workspace = true
 ethereum-types.workspace = true
 
+leansig.workspace = true
+
 ethereum_ssz_derive = "0.10.0"
 ethereum_ssz = "0.10.0"
 ssz_types = "0.14.0"
diff --git a/crates/common/types/src/attestation.rs b/crates/common/types/src/attestation.rs
index e6d377f8..dbb50d52 100644
--- a/crates/common/types/src/attestation.rs
+++ b/crates/common/types/src/attestation.rs
@@ -1,8 +1,11 @@
-use ssz_types::typenum::N4096;
+use ssz_derive::{Decode, Encode};
+use ssz_types::typenum::U4096;
+use tree_hash_derive::TreeHash;
 
 use crate::state::Checkpoint;
 
 /// Validator specific attestation wrapping shared attestation data.
+#[derive(Debug, Clone, Encode, Decode, TreeHash)]
 pub struct Attestation {
     /// The index of the validator making the attestation.
     pub validator_id: u64,
@@ -12,6 +15,7 @@ pub struct Attestation {
 }
 
 /// Attestation content describing the validator's observed chain view.
+#[derive(Debug, Clone, Encode, Decode, TreeHash)]
 pub struct AttestationData {
     /// The slot for which the attestation is made.
     pub slot: u64,
@@ -28,4 +32,4 @@ pub struct AttestationData {
 
 /// List of validator attestations included in a block.
 /// Size limited to [`crate::state::VALIDATOR_REGISTRY_LIMIT`].
-pub type Attestations = ssz_types::VariableList<Attestation, N4096>;
+pub type Attestations = ssz_types::VariableList<Attestation, U4096>;
diff --git a/crates/common/types/src/block.rs b/crates/common/types/src/block.rs
index 30391870..b204a1ae 100644
--- a/crates/common/types/src/block.rs
+++ b/crates/common/types/src/block.rs
@@ -1,11 +1,15 @@
-use ssz_types::typenum::N4096;
+use ssz_derive::{Decode, Encode};
+use ssz_types::typenum::U4096;
+use tree_hash_derive::TreeHash;
 
 use crate::{
     attestation::{Attestation, Attestations},
     primitives::H256,
+    signature::Signature,
 };
 
 /// Envelope carrying a block, an attestation from proposer, and aggregated signatures.
+#[derive(Clone, Encode, Decode)]
 pub struct SignedBlockWithAttestation {
     /// The block plus an attestation from proposer being signed.
     pub message: BlockWithAttestation,
@@ -22,15 +26,22 @@ pub struct SignedBlockWithAttestation {
     pub signature: BlockSignatures,
 }
 
+// Manual Debug impl because leanSig signatures don't implement Debug.
+impl core::fmt::Debug for SignedBlockWithAttestation {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        f.debug_struct("SignedBlockWithAttestation")
+            .field("message", &self.message)
+            .field("signature", &"...")
+            .finish()
+    }
+}
+
 /// Aggregated signature list included alongside the block.
 /// Size limited to [`crate::state::VALIDATOR_REGISTRY_LIMIT`].
-pub type BlockSignatures = ssz_types::VariableList<
-    // TODO: change to Signature type when available
-    u64,
-    N4096,
->;
+pub type BlockSignatures = ssz_types::VariableList<Signature, U4096>;
 
 /// Bundle containing a block and the proposer's attestation.
+#[derive(Debug, Clone, Encode, Decode, TreeHash)]
 pub struct BlockWithAttestation {
     /// The proposed block message.
     pub block: Block,
@@ -47,7 +58,7 @@ pub struct BlockWithAttestation {
 ///
 /// Headers are smaller than full blocks. They're useful for tracking the chain
 /// without storing everything.
-#[derive(Debug)]
+#[derive(Debug, Clone, Encode, Decode, TreeHash)]
 pub struct BlockHeader {
     /// The slot in which the block was proposed
     pub slot: u64,
@@ -62,6 +73,7 @@ pub struct BlockHeader {
 }
 
 /// A complete block including header and body.
+#[derive(Debug, Clone, Encode, Decode, TreeHash)]
 pub struct Block {
     /// The slot in which the block was proposed.
     pub slot: u64,
@@ -79,6 +91,7 @@ pub struct Block {
 ///
 /// Currently, the main operation is voting. Validators submit attestations which are
 /// packaged into blocks.
+#[derive(Debug, Clone, Encode, Decode, TreeHash)]
 pub struct BlockBody {
     /// Plain validator attestations carried in the block body.
     ///
diff --git a/crates/common/types/src/lib.rs b/crates/common/types/src/lib.rs
index f6637042..d344562c 100644
--- a/crates/common/types/src/lib.rs
+++ b/crates/common/types/src/lib.rs
@@ -2,4 +2,5 @@ pub mod attestation;
 pub mod block;
 pub mod genesis;
 pub mod primitives;
+pub mod signature;
 pub mod state;
diff --git a/crates/common/types/src/signature.rs b/crates/common/types/src/signature.rs
new file mode 100644
index 00000000..d1c6715a
--- /dev/null
+++ b/crates/common/types/src/signature.rs
@@ -0,0 +1,7 @@
+use leansig::signature::SignatureScheme;
+
+type LeanSignatureScheme = leansig::signature::generalized_xmss::instantiations_poseidon_top_level::lifetime_2_to_the_32::hashing_optimized::SIGTopLevelTargetSumLifetime32Dim64Base8;
+
+type LeanSigSignature = <LeanSignatureScheme as SignatureScheme>::Signature;
+
+pub type Signature = LeanSigSignature;

From 301cbed0d75f7debd6dccd6187ccdb1dc94536e5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tom=C3=A1s=20Gr=C3=BCner?=
 <47506558+MegaRedHand@users.noreply.github.com>
Date: Thu, 8 Jan 2026 13:15:58 -0300
Subject: [PATCH 08/10] feat: decode received blocks

---
 crates/common/types/src/block.rs     |  7 ++++---
 crates/common/types/src/signature.rs |  3 +++
 crates/net/p2p/Cargo.toml            |  2 ++
 crates/net/p2p/src/gossipsub.rs      | 30 ++++++++++------------------
 4 files changed, 20 insertions(+), 22 deletions(-)

diff --git a/crates/common/types/src/block.rs b/crates/common/types/src/block.rs
index b204a1ae..8d261b7c 100644
--- a/crates/common/types/src/block.rs
+++ b/crates/common/types/src/block.rs
@@ -1,11 +1,11 @@
 use ssz_derive::{Decode, Encode};
-use ssz_types::typenum::U4096;
+use ssz_types::typenum::{Diff, U488, U3600, U4096};
 use tree_hash_derive::TreeHash;
 
 use crate::{
     attestation::{Attestation, Attestations},
     primitives::H256,
-    signature::Signature,
+    signature::{Signature, SignatureSize},
 };
 
 /// Envelope carrying a block, an attestation from proposer, and aggregated signatures.
@@ -38,7 +38,8 @@ impl core::fmt::Debug for SignedBlockWithAttestation {
 
 /// Aggregated signature list included alongside the block.
 /// Size limited to [`crate::state::VALIDATOR_REGISTRY_LIMIT`].
-pub type BlockSignatures = ssz_types::VariableList<Signature, U4096>;
+pub type BlockSignatures =
+    ssz_types::VariableList<ssz_types::FixedVector<u8, SignatureSize>, U4096>;
 
 /// Bundle containing a block and the proposer's attestation.
 #[derive(Debug, Clone, Encode, Decode, TreeHash)]
diff --git a/crates/common/types/src/signature.rs b/crates/common/types/src/signature.rs
index d1c6715a..4b91bb62 100644
--- a/crates/common/types/src/signature.rs
+++ b/crates/common/types/src/signature.rs
@@ -1,7 +1,10 @@
 use leansig::signature::SignatureScheme;
+use ssz_types::typenum::{Diff, U488, U3600};
 
 type LeanSignatureScheme = leansig::signature::generalized_xmss::instantiations_poseidon_top_level::lifetime_2_to_the_32::hashing_optimized::SIGTopLevelTargetSumLifetime32Dim64Base8;
 
 type LeanSigSignature = <LeanSignatureScheme as SignatureScheme>::Signature;
 
 pub type Signature = LeanSigSignature;
+
+pub type SignatureSize = Diff<U3600, U488>;
diff --git a/crates/net/p2p/Cargo.toml b/crates/net/p2p/Cargo.toml
index 9a0e8ebd..c42b8887 100644
--- a/crates/net/p2p/Cargo.toml
+++ b/crates/net/p2p/Cargo.toml
@@ -34,5 +34,7 @@ tree_hash_derive = "0.12.0"
 
 sha2 = "0.10"
 
+hex = "0.4"
+
 [dev-dependencies]
 hex = "0.4"
diff --git a/crates/net/p2p/src/gossipsub.rs b/crates/net/p2p/src/gossipsub.rs
index 07fedffb..d2f98355 100644
--- a/crates/net/p2p/src/gossipsub.rs
+++ b/crates/net/p2p/src/gossipsub.rs
@@ -1,5 +1,7 @@
 use crate::Behaviour;
+use ethlambda_types::block::SignedBlockWithAttestation;
 use libp2p::gossipsub::Event;
+use ssz::Decode;
 use tracing::{info, trace};
 
 /// Topic kind for block gossip
@@ -18,10 +20,15 @@ pub async fn handle_gossipsub_message(swarm: &mut libp2p::Swarm<Behaviour>, even
     };
     match message.topic.as_str().split("/").nth(3) {
         Some(BLOCK_TOPIC_KIND) => {
-            info!(
-                "Received block gossip message of size {} bytes",
-                message.data.len()
-            );
+            let uncompressed_size = snap::raw::decompress_len(&message.data).unwrap();
+            let mut uncompressed_data = vec![0u8; uncompressed_size];
+            snap::raw::Decoder::new()
+                .decompress(&message.data, &mut uncompressed_data)
+                .unwrap();
+
+            let signed_block =
+                SignedBlockWithAttestation::from_ssz_bytes(&uncompressed_data).unwrap();
+            info!(slot=%signed_block.message.block.slot, "Received new block");
         }
         Some(ATTESTATION_TOPIC_KIND) => {
             info!(
@@ -34,18 +41,3 @@ pub async fn handle_gossipsub_message(swarm: &mut libp2p::Swarm<Behaviour>, even
         }
     }
 }
-
-#[cfg(test)]
-mod tests {
-    #[test]
-    fn deserialize_gossipsub_block_message() {
-        let hex_data = "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-        // Add tests for gossipsub message handling here
-        let data = hex::decode(hex_data).unwrap();
-        let size = snap::raw::decompress_len(&data).unwrap();
-        let mut buf = vec![0; size];
-        let mut decoder = snap::raw::Decoder::new();
-        decoder.decompress(&data, &mut buf).unwrap();
-        assert!(!buf.is_empty());
-    }
-}

From 1e6bbe4fb1061dd243a45c0b30c9d4ad930e9e9a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tom=C3=A1s=20Gr=C3=BCner?=
 <47506558+MegaRedHand@users.noreply.github.com>
Date: Thu, 8 Jan 2026 14:29:07 -0300
Subject: [PATCH 09/10] fix: error handling

---
 crates/net/p2p/src/gossipsub.rs | 29 +++++++++++++++++++----------
 crates/net/p2p/src/lib.rs       |  2 +-
 2 files changed, 20 insertions(+), 11 deletions(-)

diff --git a/crates/net/p2p/src/gossipsub.rs b/crates/net/p2p/src/gossipsub.rs
index d2f98355..738a37e7 100644
--- a/crates/net/p2p/src/gossipsub.rs
+++ b/crates/net/p2p/src/gossipsub.rs
@@ -1,15 +1,14 @@
-use crate::Behaviour;
 use ethlambda_types::block::SignedBlockWithAttestation;
 use libp2p::gossipsub::Event;
 use ssz::Decode;
-use tracing::{info, trace};
+use tracing::{error, info, trace};
 
 /// Topic kind for block gossip
 pub const BLOCK_TOPIC_KIND: &str = "block";
 /// Topic kind for attestation gossip
 pub const ATTESTATION_TOPIC_KIND: &str = "attestation";
 
-pub async fn handle_gossipsub_message(swarm: &mut libp2p::Swarm<Behaviour>, event: Event) {
+pub async fn handle_gossipsub_message(event: Event) {
     let Event::Message {
         propagation_source: _,
         message_id: _,
@@ -20,14 +19,17 @@ pub async fn handle_gossipsub_message(swarm: &mut libp2p::Swarm<Behaviour>, even
     };
     match message.topic.as_str().split("/").nth(3) {
         Some(BLOCK_TOPIC_KIND) => {
-            let uncompressed_size = snap::raw::decompress_len(&message.data).unwrap();
-            let mut uncompressed_data = vec![0u8; uncompressed_size];
-            snap::raw::Decoder::new()
-                .decompress(&message.data, &mut uncompressed_data)
-                .unwrap();
+            let Ok(uncompressed_data) = decompress_message(&message.data)
+                .inspect_err(|err| error!(%err, "Failed to decompress gossipped block"))
+            else {
+                return;
+            };
 
-            let signed_block =
-                SignedBlockWithAttestation::from_ssz_bytes(&uncompressed_data).unwrap();
+            let Ok(signed_block) = SignedBlockWithAttestation::from_ssz_bytes(&uncompressed_data)
+                .inspect_err(|err| error!(?err, "Failed to decode gossipped block"))
+            else {
+                return;
+            };
             info!(slot=%signed_block.message.block.slot, "Received new block");
         }
         Some(ATTESTATION_TOPIC_KIND) => {
@@ -41,3 +43,10 @@ pub async fn handle_gossipsub_message(swarm: &mut libp2p::Swarm<Behaviour>, even
         }
     }
 }
+
+fn decompress_message(data: &[u8]) -> snap::Result<Vec<u8>> {
+    let uncompressed_size = snap::raw::decompress_len(&data)?;
+    let mut uncompressed_data = vec![0u8; uncompressed_size];
+    snap::raw::Decoder::new().decompress(&data, &mut uncompressed_data)?;
+    Ok(uncompressed_data)
+}
diff --git a/crates/net/p2p/src/lib.rs b/crates/net/p2p/src/lib.rs
index b4441ace..8590a613 100644
--- a/crates/net/p2p/src/lib.rs
+++ b/crates/net/p2p/src/lib.rs
@@ -133,7 +133,7 @@ async fn event_loop(mut swarm: libp2p::Swarm<Behaviour>) {
             SwarmEvent::Behaviour(BehaviourEvent::Gossipsub(
                 message @ libp2p::gossipsub::Event::Message { .. },
             )) => {
-                gossipsub::handle_gossipsub_message(&mut swarm, message).await;
+                gossipsub::handle_gossipsub_message(message).await;
             }
             _ => {
                 trace!(?event, "Ignored swarm event");

From db07565a94a78c726c69822d0fdc03f0f271a91d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tom=C3=A1s=20Gr=C3=BCner?=
 <47506558+MegaRedHand@users.noreply.github.com>
Date: Thu, 8 Jan 2026 14:41:27 -0300
Subject: [PATCH 10/10] feat: add Store type

---
 Cargo.lock                             |  3 +
 crates/common/types/src/attestation.rs | 11 +++-
 crates/common/types/src/state.rs       |  2 +-
 crates/storage/Cargo.toml              |  1 +
 crates/storage/src/lib.rs              | 85 ++++++++++++++++++++++++++
 5 files changed, 100 insertions(+), 2 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 39432a69..61b0e7ee 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1785,6 +1785,9 @@ version = "0.1.0"
 [[package]]
 name = "ethlambda-storage"
 version = "0.1.0"
+dependencies = [
+ "ethlambda-types",
+]
 
 [[package]]
 name = "ethlambda-types"
diff --git a/crates/common/types/src/attestation.rs b/crates/common/types/src/attestation.rs
index dbb50d52..4b66c623 100644
--- a/crates/common/types/src/attestation.rs
+++ b/crates/common/types/src/attestation.rs
@@ -2,7 +2,7 @@ use ssz_derive::{Decode, Encode};
 use ssz_types::typenum::U4096;
 use tree_hash_derive::TreeHash;
 
-use crate::state::Checkpoint;
+use crate::{signature::Signature, state::Checkpoint};
 
 /// Validator specific attestation wrapping shared attestation data.
 #[derive(Debug, Clone, Encode, Decode, TreeHash)]
@@ -33,3 +33,12 @@ pub struct AttestationData {
 /// List of validator attestations included in a block.
 /// Size limited to [`crate::state::VALIDATOR_REGISTRY_LIMIT`].
 pub type Attestations = ssz_types::VariableList<Attestation, U4096>;
+
+/// Validator attestation bundled with its signature.
+#[derive(Clone, Encode, Decode)]
+pub struct SignedAttestation {
+    /// The attestation message signed by the validator.
+    message: Attestation,
+    /// Signature aggregation produced by the leanVM (SNARKs in the future).
+    signature: Signature,
+}
diff --git a/crates/common/types/src/state.rs b/crates/common/types/src/state.rs
index 234cf0f3..6b125c5e 100644
--- a/crates/common/types/src/state.rs
+++ b/crates/common/types/src/state.rs
@@ -8,7 +8,7 @@ use crate::{block::BlockHeader, genesis::Genesis, primitives::H256};
 pub const VALIDATOR_REGISTRY_LIMIT: u64 = 4096; // 2 ** 12
 
 /// The main consensus state object
-#[derive(Debug)]
+#[derive(Debug, Clone)]
 pub struct State {
     /// The chain's configuration parameters
     config: NetworkConfig,
diff --git a/crates/storage/Cargo.toml b/crates/storage/Cargo.toml
index 6e52d165..06cfc91a 100644
--- a/crates/storage/Cargo.toml
+++ b/crates/storage/Cargo.toml
@@ -10,3 +10,4 @@ rust-version.workspace = true
 version.workspace = true
 
 [dependencies]
+ethlambda-types.workspace = true
diff --git a/crates/storage/src/lib.rs b/crates/storage/src/lib.rs
index e69de29b..92b9c89d 100644
--- a/crates/storage/src/lib.rs
+++ b/crates/storage/src/lib.rs
@@ -0,0 +1,85 @@
+use std::collections::HashMap;
+
+use ethlambda_types::{
+    attestation::SignedAttestation,
+    block::Block,
+    primitives::H256,
+    state::{Checkpoint, State},
+};
+
+/// Forkchoice store tracking chain state and validator attestations.
+///
+/// This is the "local view" that a node uses to run LMD GHOST. It contains:
+///
+/// - which blocks and states are known,
+/// - which checkpoints are justified and finalized,
+/// - which block is currently considered the head,
+/// - and, for each validator, their latest attestation that should influence fork choice.
+///
+/// The `Store` is updated whenever:
+/// - a new block is processed,
+/// - an attestation is received (via a block or gossip),
+/// - an interval tick occurs (activating new attestations),
+/// - or when the head is recomputed.
+#[derive(Clone)]
+pub struct Store {
+    /// Current time in intervals since genesis.
+    time: u64,
+
+    /// Chain configuration parameters.
+    // config: Config,
+
+    /// Root of the current canonical chain head block.
+    ///
+    /// This is the result of running the fork choice algorithm on the current contents of the `Store`.
+    head: H256,
+
+    /// Root of the current safe target for attestation.
+    ///
+    /// This can be used by higher-level logic to restrict which blocks are
+    /// considered safe to attest to, based on additional safety conditions.
+    ///
+    safe_target: H256,
+
+    /// Highest slot justified checkpoint known to the store.
+    ///
+    /// LMD GHOST starts from this checkpoint when computing the head.
+    ///
+    /// Only descendants of this checkpoint are considered viable.
+    latest_justified: Checkpoint,
+
+    /// Highest slot finalized checkpoint known to the store.
+    ///
+    /// Everything strictly before this checkpoint can be considered immutable.
+    ///
+    /// Fork choice will never revert finalized history.
+    latest_finalized: Checkpoint,
+
+    /// Mapping from block root to Block objects.
+    ///
+    /// This is the set of blocks that the node currently knows about.
+    ///
+    /// Every block that might participate in fork choice must appear here.
+    blocks: HashMap<H256, Block>,
+
+    /// Mapping from state root to State objects.
+    ///
+    /// For each known block, we keep its post-state.
+    ///
+    /// These states carry justified and finalized checkpoints that we use to update the
+    /// `Store`'s latest justified and latest finalized checkpoints.
+    states: HashMap<H256, State>,
+
+    /// Latest signed attestations by validator that have been processed.
+    ///
+    /// - These attestations are "known" and contribute to fork choice weights.
+    /// - Keyed by validator index to enforce one attestation per validator.
+    latest_known_attestations: HashMap<u64, SignedAttestation>,
+
+    /// Latest signed attestations by validator that are pending processing.
+    ///
+    /// - These attestations are "new" and do not yet contribute to fork choice.
+    /// - They migrate to `latest_known_attestations` via interval ticks.
+    /// - Keyed by validator index to enforce one attestation per validator.
+    latest_new_attestations: HashMap<u64, SignedAttestation>,
+}