diff --git a/matrix_sdk_crypto/src/verification/sas.rs b/matrix_sdk_crypto/src/verification/sas.rs
index 4cc32b5e..cbcfc969 100644
--- a/matrix_sdk_crypto/src/verification/sas.rs
+++ b/matrix_sdk_crypto/src/verification/sas.rs
@@ -13,6 +13,7 @@
 // limitations under the License.
 
 use std::mem;
+use std::sync::{Arc, Mutex};
 
 use olm_rs::sas::OlmSas;
 
@@ -35,6 +36,7 @@ use crate::{Account, Device};
 
 /// Struct containing the protocols that were agreed to be used for the SAS
 /// flow.
+#[derive(Clone, Debug)]
 struct AcceptedProtocols {
     method: VerificationMethod,
     key_agreement_protocol: KeyAgreementProtocol,
@@ -65,16 +67,16 @@ impl From<AcceptEventContent> for AcceptedProtocols {
 /// and the specific state.
 struct Sas<S> {
     /// The Olm SAS struct.
-    inner: OlmSas,
+    inner: Arc<Mutex<OlmSas>>,
     /// Struct holding the identities that are doing the SAS dance.
     ids: SasIds,
     /// The unique identifier of this SAS flow.
     ///
     /// This will be the transaction id for to-device events and the relates_to
     /// field for in-room events.
-    verification_flow_id: String,
+    verification_flow_id: Arc<String>,
     /// The SAS state we're in.
-    state: S,
+    state: Arc<S>,
 }
 
 /// The initial SAS state.
@@ -90,7 +92,7 @@ struct Started {
 /// The SAS state we're going to be in after the other side accepted our
 /// verification start event.
 struct Accepted {
-    accepted_protocols: AcceptedProtocols,
+    accepted_protocols: Arc<AcceptedProtocols>,
     commitment: String,
 }
 
@@ -100,14 +102,14 @@ struct Accepted {
 /// From now on we can show the short auth string to the user.
 struct KeyReceived {
     we_started: bool,
-    accepted_protocols: AcceptedProtocols,
+    accepted_protocols: Arc<AcceptedProtocols>,
 }
 
 /// The SAS state we're going to be in after the user has confirmed that the
 /// short auth string matches. We still need to receive a MAC event from the
 /// other side.
 struct Confirmed {
-    accepted_protocols: AcceptedProtocols,
+    accepted_protocols: Arc<AcceptedProtocols>,
 }
 
 /// The SAS state we're going to be in after we receive a MAC event from the
@@ -115,8 +117,8 @@ struct Confirmed {
 /// matches.
 struct MacReceived {
     we_started: bool,
-    verified_devices: Vec<Box<DeviceId>>,
-    verified_master_keys: Vec<String>,
+    verified_devices: Arc<Vec<Box<DeviceId>>>,
+    verified_master_keys: Arc<Vec<String>>,
 }
 
 /// The SAS state indicating that the verification finished successfully.
@@ -124,8 +126,8 @@ struct MacReceived {
 /// We can now mark the device in our verified devices lits as verified and sign
 /// the master keys in the verified devices list.
 struct Done {
-    verified_devices: Vec<Box<DeviceId>>,
-    verified_master_keys: Vec<String>,
+    verified_devices: Arc<Vec<Box<DeviceId>>>,
+    verified_master_keys: Arc<Vec<String>>,
 }
 
 impl<S> Sas<S> {
@@ -153,14 +155,14 @@ impl Sas<Created> {
         let from_device: Box<DeviceId> = account.device_id().into();
 
         Sas {
-            inner: OlmSas::new(),
+            inner: Arc::new(Mutex::new(OlmSas::new())),
             ids: SasIds {
                 account,
                 other_device,
             },
-            verification_flow_id: verification_flow_id.clone(),
+            verification_flow_id: Arc::new(verification_flow_id.clone()),
 
-            state: Created {
+            state: Arc::new(Created {
                 protocol_definitions: MSasV1ContentOptions {
                     transaction_id: verification_flow_id,
                     from_device,
@@ -172,7 +174,7 @@ impl Sas<Created> {
                     message_authentication_codes: vec![MessageAuthenticationCode::HkdfHmacSha256],
                     hashes: vec![HashAlgorithm::Sha256],
                 },
-            },
+            }),
         }
     }
 
@@ -202,10 +204,10 @@ impl Sas<Created> {
             inner: self.inner,
             ids: self.ids,
             verification_flow_id: self.verification_flow_id,
-            state: Accepted {
+            state: Arc::new(Accepted {
                 commitment: content.commitment.clone(),
-                accepted_protocols: content.clone().into(),
-            },
+                accepted_protocols: Arc::new(content.clone().into()),
+            }),
         }
     }
 }
@@ -238,18 +240,18 @@ impl Sas<Started> {
         };
 
         Sas {
-            inner: OlmSas::new(),
+            inner: Arc::new(Mutex::new(OlmSas::new())),
 
             ids: SasIds {
                 account,
                 other_device,
             },
 
-            verification_flow_id: content.transaction_id.clone(),
+            verification_flow_id: Arc::new(content.transaction_id.clone()),
 
-            state: Started {
+            state: Arc::new(Started {
                 protocol_definitions: content.clone(),
-            },
+            }),
         }
     }
 
@@ -285,9 +287,11 @@ impl Sas<Started> {
     /// * `event` - The m.key.verification.key event that was sent to us by
     /// the other side. The event will be modified so it doesn't contain any key
     /// anymore.
-    fn into_key_received(mut self, event: &mut ToDeviceEvent<KeyEventContent>) -> Sas<KeyReceived> {
+    fn into_key_received(self, event: &mut ToDeviceEvent<KeyEventContent>) -> Sas<KeyReceived> {
         let accepted_protocols: AcceptedProtocols = self.get_accept_content().into();
         self.inner
+            .lock()
+            .unwrap()
             .set_their_public_key(&mem::take(&mut event.content.key))
             .expect("Can't set public key");
 
@@ -295,10 +299,10 @@ impl Sas<Started> {
             inner: self.inner,
             ids: self.ids,
             verification_flow_id: self.verification_flow_id,
-            state: KeyReceived {
+            state: Arc::new(KeyReceived {
                 we_started: false,
-                accepted_protocols,
-            },
+                accepted_protocols: Arc::new(accepted_protocols),
+            }),
         }
     }
 }
@@ -312,9 +316,11 @@ impl Sas<Accepted> {
     /// * `event` - The m.key.verification.key event that was sent to us by
     /// the other side. The event will be modified so it doesn't contain any key
     /// anymore.
-    fn into_key_received(mut self, event: &mut ToDeviceEvent<KeyEventContent>) -> Sas<KeyReceived> {
+    fn into_key_received(self, event: &mut ToDeviceEvent<KeyEventContent>) -> Sas<KeyReceived> {
         // TODO check the commitment here since we started the SAS dance.
         self.inner
+            .lock()
+            .unwrap()
             .set_their_public_key(&mem::take(&mut event.content.key))
             .expect("Can't set public key");
 
@@ -322,10 +328,10 @@ impl Sas<Accepted> {
             inner: self.inner,
             ids: self.ids,
             verification_flow_id: self.verification_flow_id,
-            state: KeyReceived {
+            state: Arc::new(KeyReceived {
                 we_started: true,
-                accepted_protocols: self.state.accepted_protocols,
-            },
+                accepted_protocols: self.state.accepted_protocols.clone(),
+            }),
         }
     }
 
@@ -335,7 +341,7 @@ impl Sas<Accepted> {
     fn get_key_content(&self) -> KeyEventContent {
         KeyEventContent {
             transaction_id: self.verification_flow_id.to_string(),
-            key: self.inner.public_key(),
+            key: self.inner.lock().unwrap().public_key(),
         }
     }
 }
@@ -348,7 +354,7 @@ impl Sas<KeyReceived> {
     fn get_key_content(&self) -> KeyEventContent {
         KeyEventContent {
             transaction_id: self.verification_flow_id.to_string(),
-            key: self.inner.public_key(),
+            key: self.inner.lock().unwrap().public_key(),
         }
     }
 
@@ -358,7 +364,7 @@ impl Sas<KeyReceived> {
     /// second element the English description of the emoji.
     fn get_emoji(&self) -> Vec<(&'static str, &'static str)> {
         get_emoji(
-            &self.inner,
+            &self.inner.lock().unwrap(),
             &self.ids,
             &self.verification_flow_id,
             self.state.we_started,
@@ -371,7 +377,7 @@ impl Sas<KeyReceived> {
     /// the short auth string.
     fn get_decimal(&self) -> (u32, u32, u32) {
         get_decimal(
-            &self.inner,
+            &self.inner.lock().unwrap(),
             &self.ids,
             &self.verification_flow_id,
             self.state.we_started,
@@ -386,17 +392,21 @@ impl Sas<KeyReceived> {
     /// * `event` - The m.key.verification.mac event that was sent to us by
     /// the other side.
     fn into_mac_received(self, event: &ToDeviceEvent<MacEventContent>) -> Sas<MacReceived> {
-        let (devices, master_keys) =
-            receive_mac_event(&self.inner, &self.ids, &self.verification_flow_id, event);
+        let (devices, master_keys) = receive_mac_event(
+            &self.inner.lock().unwrap(),
+            &self.ids,
+            &self.verification_flow_id,
+            event,
+        );
         Sas {
             inner: self.inner,
             verification_flow_id: self.verification_flow_id,
             ids: self.ids,
-            state: MacReceived {
+            state: Arc::new(MacReceived {
                 we_started: self.state.we_started,
-                verified_devices: devices,
-                verified_master_keys: master_keys,
-            },
+                verified_devices: Arc::new(devices),
+                verified_master_keys: Arc::new(master_keys),
+            }),
         }
     }
 
@@ -409,9 +419,9 @@ impl Sas<KeyReceived> {
             inner: self.inner,
             verification_flow_id: self.verification_flow_id,
             ids: self.ids,
-            state: Confirmed {
-                accepted_protocols: self.state.accepted_protocols,
-            },
+            state: Arc::new(Confirmed {
+                accepted_protocols: self.state.accepted_protocols.clone(),
+            }),
         }
     }
 }
@@ -425,18 +435,22 @@ impl Sas<Confirmed> {
     /// * `event` - The m.key.verification.mac event that was sent to us by
     /// the other side.
     fn into_done(self, event: &ToDeviceEvent<MacEventContent>) -> Sas<Done> {
-        let (devices, master_keys) =
-            receive_mac_event(&self.inner, &self.ids, &self.verification_flow_id, event);
+        let (devices, master_keys) = receive_mac_event(
+            &self.inner.lock().unwrap(),
+            &self.ids,
+            &self.verification_flow_id,
+            event,
+        );
 
         Sas {
             inner: self.inner,
             verification_flow_id: self.verification_flow_id,
             ids: self.ids,
 
-            state: Done {
-                verified_devices: devices,
-                verified_master_keys: master_keys,
-            },
+            state: Arc::new(Done {
+                verified_devices: Arc::new(devices),
+                verified_master_keys: Arc::new(master_keys),
+            }),
         }
     }
 
@@ -444,7 +458,11 @@ impl Sas<Confirmed> {
     ///
     /// The content needs to be automatically sent to the other side.
     fn get_mac_event_content(&self) -> MacEventContent {
-        get_mac_content(&self.inner, &self.ids, &self.verification_flow_id)
+        get_mac_content(
+            &self.inner.lock().unwrap(),
+            &self.ids,
+            &self.verification_flow_id,
+        )
     }
 }
 
@@ -458,10 +476,10 @@ impl Sas<MacReceived> {
             inner: self.inner,
             verification_flow_id: self.verification_flow_id,
             ids: self.ids,
-            state: Done {
-                verified_devices: self.state.verified_devices,
-                verified_master_keys: self.state.verified_master_keys,
-            },
+            state: Arc::new(Done {
+                verified_devices: self.state.verified_devices.clone(),
+                verified_master_keys: self.state.verified_master_keys.clone(),
+            }),
         }
     }
 
@@ -471,7 +489,7 @@ impl Sas<MacReceived> {
     /// second element the English description of the emoji.
     fn get_emoji(&self) -> Vec<(&'static str, &'static str)> {
         get_emoji(
-            &self.inner,
+            &self.inner.lock().unwrap(),
             &self.ids,
             &self.verification_flow_id,
             self.state.we_started,
@@ -484,7 +502,7 @@ impl Sas<MacReceived> {
     /// the short auth string.
     fn get_decimal(&self) -> (u32, u32, u32) {
         get_decimal(
-            &self.inner,
+            &self.inner.lock().unwrap(),
             &self.ids,
             &self.verification_flow_id,
             self.state.we_started,
@@ -498,11 +516,15 @@ impl Sas<Done> {
     /// The content needs to be automatically sent to the other side if it
     /// wasn't already sent.
     fn get_mac_event_content(&self) -> MacEventContent {
-        get_mac_content(&self.inner, &self.ids, &self.verification_flow_id)
+        get_mac_content(
+            &self.inner.lock().unwrap(),
+            &self.ids,
+            &self.verification_flow_id,
+        )
     }
 
     /// Get the list of verified devices.
-    fn verified_devices(&self) -> &Vec<Box<DeviceId>> {
+    fn verified_devices(&self) -> &[Box<DeviceId>] {
         &self.state.verified_devices
     }