Support cross-shard PRSS in sharded MPC circuits (in memory only for now)

ipa-core/src/bin/helper.rs

@@ -19,7 +19,7 @@
     executor::IpaRuntime,
     helpers::HelperIdentity,
     net::{ClientIdentity, IpaHttpClient, MpcHttpTransport, ShardHttpTransport},
-    sharding::Sharded,
+    sharding::ShardIndex,
     AppConfig, AppSetup, NonZeroU32PowerOfTwo,
 };
 use tokio::runtime::Runtime;
@@ -185,7 +185,8 @@
     let shard_network_config = NetworkConfig::new_shards(vec![], shard_clients_config);
     let (shard_transport, _shard_server) = ShardHttpTransport::new(
         IpaRuntime::from_tokio_runtime(&http_runtime),
-        Sharded::new(0, 1),
+        ShardIndex::FIRST,
+        ShardIndex::from(1),
         shard_server_config,
         shard_network_config,
         vec![],

ipa-core/src/helpers/transport/in_memory/config.rs

@@ -1,7 +1,7 @@
 use crate::{
     helpers::{HelperIdentity, Role, RoleAssignment},
     protocol::Gate,
-    sharding::{ShardIndex, Sharded},
+    sharding::ShardIndex,
     sync::Arc,
 };
 
@@ -90,7 +90,7 @@ pub enum InspectContext {
     MpcMessage {
         /// The shard of this instance.
         /// This is `None` for non-sharded helpers.
-        shard: Option<Sharded>,
+        shard: Option<ShardIndex>,
         /// Helper sending this stream.
         source: HelperIdentity,
         /// Helper that will receive this stream.
@@ -161,7 +161,7 @@ impl<F: Fn(&MaliciousHelperContext, &mut Vec<u8>) + Send + Sync> MaliciousHelper
 pub struct MaliciousHelperContext {
     /// The shard of this instance.
     /// This is `None` for non-sharded helpers.
-    pub shard: Option<Sharded>,
+    pub shard: Option<ShardIndex>,
     /// Helper that will receive this stream.
     pub dest: Role,
     /// Circuit gate this stream is tied to.

ipa-core/src/helpers/transport/in_memory/mod.rs

@@ -11,7 +11,7 @@ use crate::{
         in_memory_config::DynStreamInterceptor, transport::in_memory::config::passthrough,
         HandlerRef, HelperIdentity,
     },
-    sharding::Sharded,
+    sharding::ShardIndex,
     sync::{Arc, Weak},
 };
 
@@ -50,13 +50,13 @@ impl InMemoryMpcNetwork {
     pub fn with_stream_interceptor(
         handlers: [Option<HandlerRef>; 3],
         interceptor: &DynStreamInterceptor,
-        shard_context: Option<Sharded>,
+        shard: Option<ShardIndex>,
     ) -> Self {
         let [mut first, mut second, mut third]: [_; 3] = HelperIdentity::make_three().map(|i| {
             let mut config_builder = TransportConfigBuilder::for_helper(i);
             config_builder.with_interceptor(interceptor);
 
-            Setup::with_config(i, config_builder.with_sharding(shard_context))
+            Setup::with_config(i, config_builder.with_sharding(shard))
         });
 
         first.connect(&mut second);

ipa-core/src/helpers/transport/in_memory/sharding.rs

@@ -4,7 +4,7 @@ use crate::{
         transport::in_memory::transport::{InMemoryTransport, Setup, TransportConfigBuilder},
         HelperIdentity,
     },
-    sharding::{ShardIndex, Sharded},
+    sharding::ShardIndex,
     sync::{Arc, Weak},
 };
 
@@ -37,15 +37,7 @@ impl InMemoryShardNetwork {
 
             let mut shard_connections = shard_count
                 .iter()
-                .map(|i| {
-                    Setup::with_config(
-                        i,
-                        config_builder.with_sharding(Some(Sharded {
-                            shard_id: i,
-                            shard_count,
-                        })),
-                    )
-                })
+                .map(|i| Setup::with_config(i, config_builder.with_sharding(Some(i))))
                 .collect::<Vec<_>>();
             for i in 0..shard_connections.len() {
                 let (lhs, rhs) = shard_connections.split_at_mut(i);

ipa-core/src/helpers/transport/in_memory/transport.rs

@@ -28,7 +28,7 @@ use crate::{
         Transport, TransportIdentity,
     },
     protocol::{Gate, QueryId},
-    sharding::Sharded,
+    sharding::ShardIndex,
     sync::{Arc, Weak},
 };
 
@@ -192,8 +192,8 @@ impl<I: TransportIdentity> Transport for Weak<InMemoryTransport<I>> {
         let gate = addr.gate.clone();
 
         let (ack_tx, ack_rx) = oneshot::channel();
-        let context = gate
-            .map(|gate| dest.inspect_context(this.config.shard_config, this.config.identity, gate));
+        let context =
+            gate.map(|gate| dest.inspect_context(this.config.shard, this.config.identity, gate));
 
         channel
             .send((
@@ -628,7 +628,7 @@ mod tests {
 }
 
 pub struct TransportConfig {
-    pub shard_config: Option<Sharded>,
+    pub shard: Option<ShardIndex>,
     pub identity: HelperIdentity,
     pub stream_interceptor: DynStreamInterceptor,
 }
@@ -652,17 +652,17 @@ impl TransportConfigBuilder {
         self
     }
 
-    pub fn with_sharding(&self, shard_config: Option<Sharded>) -> TransportConfig {
+    pub fn with_sharding(&self, shard: Option<ShardIndex>) -> TransportConfig {
         TransportConfig {
-            shard_config,
+            shard,
             identity: self.identity,
             stream_interceptor: Arc::clone(&self.stream_interceptor),
         }
     }
 
     pub fn not_sharded(&self) -> TransportConfig {
         TransportConfig {
-            shard_config: None,
+            shard: None,
             identity: self.identity,
             stream_interceptor: Arc::clone(&self.stream_interceptor),
         }

ipa-core/src/helpers/transport/mod.rs

@@ -9,8 +9,6 @@
 
 #[cfg(feature = "in-memory-infra")]
 use crate::helpers::in_memory_config::InspectContext;
-#[cfg(feature = "in-memory-infra")]
-use crate::sharding::Sharded;
 use crate::{
     helpers::{transport::routing::RouteId, HelperIdentity, Role, TransportIdentity},
     protocol::{Gate, QueryId},
@@ -58,7 +56,7 @@
     #[cfg(feature = "in-memory-infra")]
     fn inspect_context(
         &self,
-        shard: Option<Sharded>,
+        shard: Option<ShardIndex>,
         helper: HelperIdentity,
         gate: Gate,
     ) -> InspectContext;
@@ -84,13 +82,13 @@
     #[cfg(feature = "in-memory-infra")]
     fn inspect_context(
         &self,
-        shard: Option<Sharded>,
+        shard: Option<ShardIndex>,
         helper: HelperIdentity,
         gate: Gate,
     ) -> InspectContext {
         InspectContext::ShardMessage {
             helper,
-            source: shard.unwrap().shard_id,
+            source: shard.unwrap(),
             dest: *self,
             gate,
         }
@@ -125,7 +123,7 @@
     #[cfg(feature = "in-memory-infra")]
     fn inspect_context(
         &self,
-        shard: Option<Sharded>,
+        shard: Option<ShardIndex>,
         helper: HelperIdentity,
         gate: Gate,
     ) -> InspectContext {
@@ -167,7 +165,7 @@
     #[cfg(feature = "in-memory-infra")]
     fn inspect_context(
         &self,
-        _shard: Option<Sharded>,
+        _shard: Option<ShardIndex>,
         _helper: HelperIdentity,
         _gate: Gate,
     ) -> InspectContext {

ipa-core/src/net/test.rs

@@ -246,10 +246,8 @@ impl TestApp {
         );
         let (shard_transport, shard_server) = super::ShardHttpTransport::new(
             IpaRuntime::current(),
-            crate::sharding::Sharded {
-                shard_id: sid.shard_index,
-                shard_count: self.shard_network_config.shard_count(),
-            },
+            sid.shard_index,
+            self.shard_network_config.shard_count(),
             self.shard_server.config,
             self.shard_network_config,
             shard_clients,

ipa-core/src/net/transport.rs

@@ -22,7 +22,7 @@
     },
     net::{client::IpaHttpClient, error::Error, IpaHttpServer},
     protocol::{Gate, QueryId},
-    sharding::{ShardIndex, Sharded},
+    sharding::ShardIndex,
     sync::Arc,
 };
 
@@ -45,7 +45,7 @@
 #[derive(Clone)]
 pub struct ShardHttpTransport {
     pub(super) inner_transport: Arc<HttpTransport<Shard>>,
-    pub(super) shard_config: Sharded,
+    pub(super) shard_count: ShardIndex,
 }
 
 impl RouteParams<RouteId, NoQueryId, NoStep> for QueryConfig {
@@ -297,7 +297,9 @@
     #[must_use]
     pub fn new(
         http_runtime: IpaRuntime,
-        shard_config: Sharded,
+        // todo: maybe a wrapper struct for it
+        shard_id: ShardIndex,
+        shard_count: ShardIndex,
         server_config: ServerConfig,
         network_config: NetworkConfig<Shard>,
         clients: Vec<IpaHttpClient<Shard>>,
@@ -306,12 +308,12 @@
         let transport = Self {
             inner_transport: Arc::new(HttpTransport {
                 http_runtime,
-                identity: shard_config.shard_id,
+                identity: shard_id,
                 clients,
                 handler,
                 record_streams: StreamCollection::default(),
             }),
-            shard_config,
+            shard_count,
         };
 
         let server = IpaHttpServer::new_shards(&transport, server_config, network_config);
@@ -331,10 +333,7 @@
 
     fn peers(&self) -> impl Iterator<Item = Self::Identity> {
         let this = self.identity();
-        self.shard_config
-            .shard_count
-            .iter()
-            .filter(move |&v| v != this)
+        self.shard_count.iter().filter(move |&v| v != this)
     }
 
     async fn send<D, Q, S, R>(

ipa-core/src/protocol/context/dzkp_semi_honest.rs

@@ -52,6 +52,10 @@
     fn shard_recv_channel<M: Message>(&self, origin: ShardIndex) -> ShardReceivingEnd<M> {
         self.inner.shard_recv_channel(origin)
     }
+
+    fn cross_shard_prss(&self) -> InstrumentedIndexedSharedRandomness<'_> {
+        self.inner.cross_shard_prss()
+    }
 }
 
 impl<'a, B: ShardBinding> super::Context for DZKPUpgraded<'a, B> {

ipa-core/src/protocol/context/malicious.rs

@@ -74,6 +74,10 @@
     fn shard_recv_channel<M: Message>(&self, origin: ShardIndex) -> ShardReceivingEnd<M> {
         self.inner.shard_recv_channel(origin)
     }
+
+    fn cross_shard_prss(&self) -> InstrumentedIndexedSharedRandomness<'_> {
+        self.inner.cross_shard_prss()
+    }
 }
 
 impl<'a> Context<'a, NotSharded> {

ipa-core/src/protocol/context/mod.rs

@@ -211,6 +211,14 @@ impl ShardedContext for Base<'_, Sharded> {
             .gateway
             .get_shard_receiver(&ChannelId::new(origin, self.gate.clone()))
     }
+
+    fn cross_shard_prss(&self) -> InstrumentedIndexedSharedRandomness<'_> {
+        InstrumentedIndexedSharedRandomness::new(
+            self.sharding.cross_shard_prss().indexed(self.gate()),
+            self.gate(),
+            self.inner.gateway.role(),
+        )
+    }
 }
 
 impl<'a, B: ShardBinding> Context for Base<'a, B> {
@@ -325,6 +333,13 @@ pub trait ShardedContext: Context + ShardConfiguration {
 
         ShardIndex::from(shard_index)
     }
+
+    /// Get the indexed PRSS instance shared across all shards on this helper.
+    /// Each shard will see the same random values generated by it.
+    /// This is still PRSS - the corresponding shards on other helpers will share
+    /// the left and the right part
+    #[must_use]
+    fn cross_shard_prss(&self) -> InstrumentedIndexedSharedRandomness<'_>;
 }
 
 impl ShardConfiguration for Base<'_, Sharded> {

ipa-core/src/protocol/context/semi_honest.rs

@@ -97,6 +97,10 @@
     fn shard_recv_channel<M: Message>(&self, origin: ShardIndex) -> ShardReceivingEnd<M> {
         self.inner.shard_recv_channel(origin)
     }
+
+    fn cross_shard_prss(&self) -> InstrumentedIndexedSharedRandomness<'_> {
+        self.inner.cross_shard_prss()
+    }
 }
 
 impl<'a, B: ShardBinding> super::Context for Context<'a, B> {
@@ -218,6 +222,10 @@
     fn shard_recv_channel<M: Message>(&self, origin: ShardIndex) -> ShardReceivingEnd<M> {
         self.inner.shard_recv_channel(origin)
     }
+
+    fn cross_shard_prss(&self) -> InstrumentedIndexedSharedRandomness<'_> {
+        self.inner.cross_shard_prss()
+    }
 }
 
 impl<'a, B: ShardBinding, F: ExtendableField> super::Context for Upgraded<'a, B, F> {

ipa-core/src/protocol/ipa_prf/shuffle/malicious.rs

@@ -867,7 +867,7 @@ mod tests {
         // changing x2
         if ctx.gate.as_ref().contains("transfer_x_y")
             && ctx.dest == Role::H2
-            && ctx.shard.map(|s| s.shard_id) == target_shard
+            && ctx.shard == target_shard
         {
             data[0] ^= 1u8;
         }
@@ -883,7 +883,7 @@ mod tests {
         // changing y1
         if ctx.gate.as_ref().contains("transfer_x_y")
             && ctx.dest == Role::H3
-            && ctx.shard.map(|s| s.shard_id) == target_shard
+            && ctx.shard == target_shard
         {
             data[0] ^= 1u8;
         }
@@ -899,7 +899,7 @@ mod tests {
         // changing c_hat_2
         if ctx.gate.as_ref().contains("transfer_c")
             && ctx.dest == Role::H2
-            && ctx.shard.map(|s| s.shard_id) == target_shard
+            && ctx.shard == target_shard
         {
             data[0] ^= 1u8;
         }