diff --git a/src/async_client.rs b/src/async_client.rs
index 8dc8b1fd..f74e469e 100644
--- a/src/async_client.rs
+++ b/src/async_client.rs
@@ -375,7 +375,7 @@ impl AsyncClient {
             timeout: sync_settings.timeout,
         };
 
-        let response = self.send(request).await?;
+        let mut response = self.send(request).await?;
 
         for (room_id, room) in &response.rooms.join {
             let room_id = room_id.to_string();
@@ -418,7 +418,7 @@ impl AsyncClient {
         }
 
         let mut client = self.base_client.write().await;
-        client.receive_sync_response(&response);
+        client.receive_sync_response(&mut response).await;
 
         Ok(response)
     }
diff --git a/src/base_client.rs b/src/base_client.rs
index 0cbc7170..a6283902 100644
--- a/src/base_client.rs
+++ b/src/base_client.rs
@@ -294,8 +294,20 @@ impl Client {
     /// # Arguments
     ///
     /// * `response` - The response that we received after a successful sync.
-    pub fn receive_sync_response(&mut self, response: &api::sync::sync_events::IncomingResponse) {
+    pub async fn receive_sync_response(
+        &mut self,
+        response: &mut api::sync::sync_events::IncomingResponse,
+    ) {
         self.sync_token = Some(response.next_batch.clone());
+
+        #[cfg(feature = "encryption")]
+        {
+            let olm = self.olm.lock().await;
+
+            if let Some(o) = &*olm {
+                o.receive_sync_response(response);
+            }
+        }
     }
 
     /// Should account or one-time keys be uploaded to the server.
diff --git a/src/crypto/machine.rs b/src/crypto/machine.rs
index 5419425a..f2a5e830 100644
--- a/src/crypto/machine.rs
+++ b/src/crypto/machine.rs
@@ -29,7 +29,11 @@ use serde_json::Value;
 use ruma_client_api::r0::keys::{
     AlgorithmAndDeviceId, DeviceKeys, KeyAlgorithm, OneTimeKey, SignedKey,
 };
-use ruma_events::Algorithm;
+use ruma_client_api::r0::sync::sync_events::IncomingResponse as SyncResponse;
+use ruma_events::{
+    to_device::{ToDevice as ToDeviceEvent, ToDeviceEncrypted, ToDeviceRoomKeyRequest},
+    Algorithm, EventResult,
+};
 use ruma_identifiers::{DeviceId, UserId};
 
 pub type OneTimeKeys = HashMap<AlgorithmAndDeviceId, OneTimeKey>;
@@ -311,6 +315,54 @@ impl OlmMachine {
 
         Ok((device_keys, one_time_keys))
     }
+
+    /// Decrypt a to-device event.
+    ///
+    /// Returns a decrypted `ToDeviceEvent` if the decryption was successful,
+    /// an error indicating why decryption failed otherwise.
+    ///
+    /// # Arguments
+    ///
+    /// * `event` - The to-device event that should be decrypted.
+    fn decrypt_to_device_event(&self, _: &ToDeviceEncrypted) -> Result<ToDeviceEvent, ()> {
+        Err(())
+    }
+
+    fn handle_room_key_request(&self, _: &ToDeviceRoomKeyRequest) {
+        // TODO handle room key requests here.
+    }
+
+    fn handle_verification_event(&self, _: &ToDeviceEvent) {
+        // TODO handle to-device verification events here.
+    }
+
+    pub fn receive_sync_response(&self, response: &mut SyncResponse) {
+        for event in response.to_device.events.iter() {
+            let event = if let EventResult::Ok(e) = event {
+                e
+            } else {
+                // Skip invalid events.
+                // TODO log here
+                continue;
+            };
+
+            match event {
+                ToDeviceEvent::RoomEncrypted(e) => {
+                    // TODO put the decrypted event into a vec so we can replace
+                    // them in the sync response.
+                    let _ = self.decrypt_to_device_event(e);
+                }
+                ToDeviceEvent::RoomKeyRequest(e) => self.handle_room_key_request(e),
+                ToDeviceEvent::KeyVerificationAccept(..)
+                | ToDeviceEvent::KeyVerificationCancel(..)
+                | ToDeviceEvent::KeyVerificationKey(..)
+                | ToDeviceEvent::KeyVerificationMac(..)
+                | ToDeviceEvent::KeyVerificationRequest(..)
+                | ToDeviceEvent::KeyVerificationStart(..) => self.handle_verification_event(event),
+                _ => continue,
+            }
+        }
+    }
 }
 
 #[cfg(test)]