diff --git a/services/identity/src/service.rs b/services/identity/src/service.rs
index b4f219870..7ab4feab3 100644
--- a/services/identity/src/service.rs
+++ b/services/identity/src/service.rs
@@ -1,583 +1,609 @@
 use aws_sdk_dynamodb::output::GetItemOutput;
 use aws_sdk_dynamodb::Error as DynamoDBError;
 use chrono::Utc;
 use comm_opaque::Cipher;
 use constant_time_eq::constant_time_eq;
 use futures_core::Stream;
 use opaque_ke::{
   CredentialFinalization, CredentialRequest,
   RegistrationRequest as PakeRegistrationRequest, ServerLogin,
   ServerLoginStartParameters,
 };
 use opaque_ke::{RegistrationUpload, ServerRegistration};
 use rand::rngs::OsRng;
 use rand::{CryptoRng, Rng};
 use siwe::Message;
-use std::collections::HashSet;
+use std::collections::{HashMap, HashSet};
 use std::pin::Pin;
 use tokio::sync::mpsc;
 use tokio_stream::{wrappers::ReceiverStream, StreamExt};
 use tonic::{Request, Response, Status};
 use tracing::{error, info, instrument};
 
 use crate::config::CONFIG;
 use crate::constants::MPSC_CHANNEL_BUFFER_CAPACITY;
 use crate::database::{DatabaseClient, Error as DBError};
 use crate::nonce::generate_nonce_data;
 use crate::token::{AccessTokenData, AuthType};
 
 pub use proto::identity_service_server::IdentityServiceServer;
 use proto::{
   get_user_id_request::AuthType as ProtoAuthType,
   identity_service_server::IdentityService,
   login_request::Data::PakeLoginRequest,
   login_request::Data::WalletLoginRequest,
   login_response::Data::PakeLoginResponse,
   login_response::Data::WalletLoginResponse,
   pake_login_request::Data::PakeCredentialFinalization,
   pake_login_request::Data::PakeCredentialRequestAndUserId,
   pake_login_response::Data::AccessToken,
   pake_login_response::Data::PakeCredentialResponse,
   registration_request::Data::PakeCredentialFinalization as PakeRegistrationCredentialFinalization,
   registration_request::Data::PakeRegistrationRequestAndUserId,
   registration_request::Data::PakeRegistrationUploadAndCredentialRequest,
   registration_response::Data::PakeLoginResponse as PakeRegistrationLoginResponse,
   registration_response::Data::PakeRegistrationResponse, CompareUsersRequest,
   CompareUsersResponse, DeleteUserRequest, DeleteUserResponse,
-  GenerateNonceRequest, GenerateNonceResponse, GetUserIdRequest,
-  GetUserIdResponse, LoginRequest, LoginResponse,
+  GenerateNonceRequest, GenerateNonceResponse,
+  GetSessionInitializationInfoRequest, GetSessionInitializationInfoResponse,
+  GetUserIdRequest, GetUserIdResponse, LoginRequest, LoginResponse,
   PakeLoginRequest as PakeLoginRequestStruct,
   PakeLoginResponse as PakeLoginResponseStruct, RegistrationRequest,
-  RegistrationResponse, VerifyUserTokenRequest, VerifyUserTokenResponse,
-  WalletLoginRequest as WalletLoginRequestStruct,
+  RegistrationResponse, SessionInitializationInfo, VerifyUserTokenRequest,
+  VerifyUserTokenResponse, WalletLoginRequest as WalletLoginRequestStruct,
   WalletLoginResponse as WalletLoginResponseStruct,
 };
 
 mod proto {
   tonic::include_proto!("identity");
 }
 
 mod login;
 mod registration;
 
 #[derive(Debug)]
 enum PakeWorkflow {
   Registration,
   Login,
 }
 
 #[derive(derive_more::Constructor)]
 pub struct MyIdentityService {
   client: DatabaseClient,
 }
 
 #[tonic::async_trait]
 impl IdentityService for MyIdentityService {
   type RegisterUserStream = Pin<
     Box<
       dyn Stream<Item = Result<RegistrationResponse, Status>> + Send + 'static,
     >,
   >;
 
   #[instrument(skip(self))]
   async fn register_user(
     &self,
     request: Request<tonic::Streaming<RegistrationRequest>>,
   ) -> Result<Response<Self::RegisterUserStream>, Status> {
     let mut in_stream = request.into_inner();
     let (tx, rx) = mpsc::channel(MPSC_CHANNEL_BUFFER_CAPACITY);
     let first_message = in_stream.next().await;
     let mut registration_state = registration::handle_registration_request(
       first_message,
       self.client.clone(),
       tx.clone(),
     )
     .await?;
     // ServerRegistration in opaque-ke v1.2 doesn't implement Clone, so we
     // have to take the value out of registration_state, replacing it with None
     let pake_state =
       if let Some(pake_state) = registration_state.pake_state.take() {
         pake_state
       } else {
         error!("registration_state is missing opaque-ke ServerRegistration");
         return Err(Status::failed_precondition("internal error"));
       };
     let second_message = in_stream.next().await;
     let server_login =
       registration::handle_registration_upload_and_credential_request(
         second_message,
         tx.clone(),
         self.client.clone(),
         &registration_state,
         pake_state,
       )
       .await?;
     let third_message = in_stream.next().await;
     registration::handle_credential_finalization(
       third_message,
       tx,
       self.client.clone(),
       &registration_state,
       server_login,
     )
     .await?;
 
     let out_stream = ReceiverStream::new(rx);
     Ok(Response::new(
       Box::pin(out_stream) as Self::RegisterUserStream
     ))
   }
 
   type LoginUserStream =
     Pin<Box<dyn Stream<Item = Result<LoginResponse, Status>> + Send + 'static>>;
 
   #[instrument(skip(self))]
   async fn login_user(
     &self,
     request: Request<tonic::Streaming<LoginRequest>>,
   ) -> Result<Response<Self::LoginUserStream>, Status> {
     let mut in_stream = request.into_inner();
     let (tx, rx) = mpsc::channel(MPSC_CHANNEL_BUFFER_CAPACITY);
 
     let first_message = in_stream.next().await;
     let login_state = login::handle_login_request(
       first_message,
       tx.clone(),
       self.client.clone(),
     )
     .await?;
 
     // login_state will be None if user is logging in with a wallet
     if let Some(state) = login_state {
       let second_message = in_stream.next().await;
       login::handle_credential_finalization(
         second_message,
         tx,
         self.client.clone(),
         state,
       )
       .await?;
     }
 
     let out_stream = ReceiverStream::new(rx);
     Ok(Response::new(Box::pin(out_stream) as Self::LoginUserStream))
   }
 
   #[instrument(skip(self))]
   async fn verify_user_token(
     &self,
     request: Request<VerifyUserTokenRequest>,
   ) -> Result<Response<VerifyUserTokenResponse>, Status> {
     info!("Received VerifyUserToken request: {:?}", request);
     let message = request.into_inner();
     let token_valid = match self
       .client
       .get_access_token_data(message.user_id, message.signing_public_key)
       .await
     {
       Ok(Some(access_token_data)) => constant_time_eq(
         access_token_data.access_token.as_bytes(),
         message.access_token.as_bytes(),
       ),
       Ok(None) => false,
       Err(e) => return Err(handle_db_error(e)),
     };
     let response = Response::new(VerifyUserTokenResponse { token_valid });
     info!("Sending VerifyUserToken response: {:?}", response);
     Ok(response)
   }
 
   #[instrument(skip(self))]
   async fn get_user_id(
     &self,
     request: Request<GetUserIdRequest>,
   ) -> Result<Response<GetUserIdResponse>, Status> {
     let message = request.into_inner();
     let auth_type = match ProtoAuthType::from_i32(message.auth_type) {
       Some(ProtoAuthType::Password) => AuthType::Password,
       Some(ProtoAuthType::Wallet) => AuthType::Wallet,
       None => {
         error!(
           "Unable to parse AuthType from message: {}",
           message.auth_type
         );
         return Err(Status::invalid_argument("invalid message"));
       }
     };
     let user_id = match self
       .client
       .get_user_id_from_user_info(message.user_info, auth_type)
       .await
     {
       Ok(Some(user_id)) => user_id,
       Ok(None) => return Err(Status::not_found("no user ID found")),
       Err(e) => return Err(handle_db_error(e)),
     };
     let response = Response::new(GetUserIdResponse { user_id });
     Ok(response)
   }
 
   #[instrument(skip(self))]
   async fn delete_user(
     &self,
     request: tonic::Request<DeleteUserRequest>,
   ) -> Result<tonic::Response<DeleteUserResponse>, tonic::Status> {
     let message = request.into_inner();
     match self.client.delete_user(message.user_id).await {
       Ok(_) => Ok(Response::new(DeleteUserResponse {})),
       Err(e) => Err(handle_db_error(e)),
     }
   }
 
   #[instrument(skip(self))]
   async fn compare_users(
     &self,
     request: Request<CompareUsersRequest>,
   ) -> Result<Response<CompareUsersResponse>, Status> {
     let message = request.into_inner();
     let mut mysql_users_vec = message.users;
     let mut ddb_users_vec = match self.client.get_users().await {
       Ok(user_list) => user_list,
       Err(e) => return Err(handle_db_error(e)),
     };
     // We use HashSets here for faster lookups
     let mysql_users_set = HashSet::<String>::from_iter(mysql_users_vec.clone());
     let ddb_users_set = HashSet::<String>::from_iter(ddb_users_vec.clone());
 
     ddb_users_vec.retain(|user| !mysql_users_set.contains(user));
     mysql_users_vec.retain(|user| !ddb_users_set.contains(user));
     Ok(Response::new(CompareUsersResponse {
       users_missing_from_keyserver: ddb_users_vec,
       users_missing_from_identity: mysql_users_vec,
     }))
   }
 
   #[instrument(skip(self))]
   async fn generate_nonce(
     &self,
     _request: Request<GenerateNonceRequest>,
   ) -> Result<Response<GenerateNonceResponse>, Status> {
     let nonce_data = generate_nonce_data(&mut OsRng);
     match self
       .client
       .add_nonce_to_nonces_table(nonce_data.clone())
       .await
     {
       Ok(_) => Ok(Response::new(GenerateNonceResponse {
         nonce: nonce_data.nonce,
       })),
       Err(e) => Err(handle_db_error(e)),
     }
   }
+
+  #[instrument(skip(self))]
+  async fn get_session_initialization_info(
+    &self,
+    request: Request<GetSessionInitializationInfoRequest>,
+  ) -> Result<Response<GetSessionInitializationInfoResponse>, Status> {
+    let message = request.into_inner();
+    match self
+      .client
+      .get_session_initialization_info(&message.user_id)
+      .await
+    {
+      Ok(Some(session_initialization_info)) => {
+        let mut devices = HashMap::new();
+        for (device, info) in session_initialization_info {
+          devices.insert(device, SessionInitializationInfo { info });
+        }
+        Ok(Response::new(GetSessionInitializationInfoResponse {
+          devices,
+        }))
+      }
+      Ok(None) => return Err(Status::not_found("user not found")),
+      Err(e) => Err(handle_db_error(e)),
+    }
+  }
 }
 
 async fn put_token_helper(
   client: DatabaseClient,
   auth_type: AuthType,
   user_id: &str,
   signing_public_key: &str,
   rng: &mut (impl Rng + CryptoRng),
 ) -> Result<String, Status> {
   if user_id.is_empty() || signing_public_key.is_empty() {
     error!(
       "Incomplete data: user ID \"{}\", signing public key \"{}\"",
       user_id, signing_public_key
     );
     return Err(Status::aborted("user not found"));
   }
   let access_token_data = AccessTokenData::new(
     user_id.to_string(),
     signing_public_key.to_string(),
     auth_type,
     rng,
   );
   match client
     .put_access_token_data(access_token_data.clone())
     .await
   {
     Ok(_) => Ok(access_token_data.access_token),
     Err(e) => Err(handle_db_error(e)),
   }
 }
 
 fn parse_and_verify_siwe_message(
   user_id: &str,
   signing_public_key: &str,
   siwe_message: &str,
   siwe_signature: Vec<u8>,
 ) -> Result<(), Status> {
   if user_id.is_empty() || signing_public_key.is_empty() {
     error!(
       "Incomplete data: user ID {}, signing public key {}",
       user_id, signing_public_key
     );
     return Err(Status::aborted("user not found"));
   }
   let siwe_message: Message = match siwe_message.parse() {
     Ok(m) => m,
     Err(e) => {
       error!("Failed to parse SIWE message: {}", e);
       return Err(Status::invalid_argument("invalid message"));
     }
   };
   match siwe_message.verify(
     match siwe_signature.try_into() {
       Ok(s) => s,
       Err(e) => {
         error!("Conversion to SIWE signature failed: {:?}", e);
         return Err(Status::invalid_argument("invalid message"));
       }
     },
     None,
     None,
     Some(&Utc::now()),
   ) {
     Err(e) => {
       error!(
         "Signature verification failed for user {} with signing public key {}: {}",
         user_id, signing_public_key, e
       );
       Err(Status::unauthenticated("message not authenticated"))
     }
     Ok(_) => Ok(()),
   }
 }
 
 async fn wallet_login_helper(
   client: DatabaseClient,
   wallet_login_request: WalletLoginRequestStruct,
   rng: &mut (impl Rng + CryptoRng),
 ) -> Result<LoginResponse, Status> {
   parse_and_verify_siwe_message(
     &wallet_login_request.user_id,
     &wallet_login_request.signing_public_key,
     &wallet_login_request.siwe_message,
     wallet_login_request.siwe_signature,
   )?;
   client
     .update_users_table(
       wallet_login_request.user_id.clone(),
       Some(wallet_login_request.signing_public_key.clone()),
       None,
       None,
     )
     .await
     .map_err(handle_db_error)?;
   Ok(LoginResponse {
     data: Some(WalletLoginResponse(WalletLoginResponseStruct {
       access_token: put_token_helper(
         client,
         AuthType::Wallet,
         &wallet_login_request.user_id,
         &wallet_login_request.signing_public_key,
         rng,
       )
       .await?,
     })),
   })
 }
 
 async fn pake_login_start(
   client: DatabaseClient,
   user_id: &str,
   pake_credential_request: &[u8],
 ) -> Result<LoginResponseAndPakeState, Status> {
   if user_id.is_empty() {
     error!("Incomplete data: user ID not provided");
     return Err(Status::aborted("user not found"));
   }
   let server_registration =
     match client.get_pake_registration(user_id.to_string()).await {
       Ok(Some(r)) => r,
       Ok(None) => {
         return Err(Status::not_found("user not found"));
       }
       Err(e) => return Err(handle_db_error(e)),
     };
   let credential_request =
     CredentialRequest::deserialize(pake_credential_request).map_err(|e| {
       error!("Failed to deserialize credential request: {}", e);
       Status::invalid_argument("invalid message")
     })?;
   match ServerLogin::start(
     &mut OsRng,
     server_registration,
     CONFIG.server_keypair.private(),
     credential_request,
     ServerLoginStartParameters::default(),
   ) {
     Ok(server_login_start_result) => Ok(LoginResponseAndPakeState {
       response: PakeLoginResponseStruct {
         data: Some(PakeCredentialResponse(
           server_login_start_result.message.serialize().map_err(|e| {
             error!("Failed to serialize PAKE message: {}", e);
             Status::failed_precondition("internal error")
           })?,
         )),
       },
       pake_state: server_login_start_result.state,
     }),
     Err(e) => {
       error!(
         "Encountered a PAKE protocol error when starting login: {}",
         e
       );
       Err(Status::aborted("server error"))
     }
   }
 }
 
 async fn pake_login_finish(
   user_id: &str,
   signing_public_key: &str,
   client: DatabaseClient,
   server_login: ServerLogin<Cipher>,
   pake_credential_finalization: &[u8],
   rng: &mut (impl Rng + CryptoRng),
   pake_workflow: PakeWorkflow,
 ) -> Result<PakeLoginResponseStruct, Status> {
   if user_id.is_empty() || signing_public_key.is_empty() {
     error!(
       "Incomplete data: user ID {}, signing public key {}",
       user_id, signing_public_key
     );
     return Err(Status::aborted("user not found"));
   }
   server_login
     .finish(
       CredentialFinalization::deserialize(pake_credential_finalization)
         .map_err(|e| {
           error!("Failed to deserialize credential finalization bytes: {}", e);
           Status::aborted("login failed")
         })?,
     )
     .map_err(|e| {
       error!(
         "Encountered a PAKE protocol error when finishing login: {}",
         e
       );
       Status::aborted("server error")
     })?;
   if matches!(pake_workflow, PakeWorkflow::Login) {
     client
       .update_users_table(
         user_id.to_string(),
         Some(signing_public_key.to_string()),
         None,
         None,
       )
       .await
       .map_err(handle_db_error)?;
   }
   Ok(PakeLoginResponseStruct {
     data: Some(AccessToken(
       put_token_helper(
         client,
         AuthType::Password,
         user_id,
         signing_public_key,
         rng,
       )
       .await?,
     )),
   })
 }
 
 async fn pake_registration_start(
   rng: &mut (impl Rng + CryptoRng),
   registration_request_bytes: &[u8],
 ) -> Result<RegistrationResponseAndPakeState, Status> {
   match ServerRegistration::<Cipher>::start(
     rng,
     PakeRegistrationRequest::deserialize(registration_request_bytes).unwrap(),
     CONFIG.server_keypair.public(),
   ) {
     Ok(server_registration_start_result) => {
       Ok(RegistrationResponseAndPakeState {
         response: RegistrationResponse {
           data: Some(PakeRegistrationResponse(
             server_registration_start_result.message.serialize(),
           )),
         },
         pake_state: server_registration_start_result.state,
       })
     }
     Err(e) => {
       error!(
         "Encountered a PAKE protocol error when starting registration: {}",
         e
       );
       Err(Status::aborted("server error"))
     }
   }
 }
 
 async fn pake_registration_finish(
   user_id: &str,
   client: DatabaseClient,
   registration_upload_bytes: &[u8],
   server_registration: Option<ServerRegistration<Cipher>>,
   username: &str,
   signing_public_key: &str,
 ) -> Result<(), Status> {
   if user_id.is_empty() {
     error!("Incomplete data: user ID not provided");
     return Err(Status::aborted("user not found"));
   }
   let server_registration_finish_result = server_registration
     .ok_or_else(|| Status::aborted("registration failed"))?
     .finish(
       RegistrationUpload::deserialize(registration_upload_bytes).map_err(
         |e| {
           error!("Failed to deserialize registration upload bytes: {}", e);
           Status::aborted("registration failed")
         },
       )?,
     )
     .map_err(|e| {
       error!(
         "Encountered a PAKE protocol error when finishing registration: {}",
         e
       );
       Status::aborted("server error")
     })?;
 
   match client
     .add_user_to_users_table(
       user_id.to_string(),
       server_registration_finish_result,
       username.to_string(),
       signing_public_key.to_string(),
     )
     .await
   {
     Ok(_) => Ok(()),
     Err(e) => Err(handle_db_error(e)),
   }
 }
 
 fn handle_db_error(db_error: DBError) -> Status {
   match db_error {
     DBError::AwsSdk(DynamoDBError::InternalServerError(_))
     | DBError::AwsSdk(DynamoDBError::ProvisionedThroughputExceededException(
       _,
     ))
     | DBError::AwsSdk(DynamoDBError::RequestLimitExceeded(_)) => {
       Status::unavailable("please retry")
     }
     e => {
       error!("Encountered an unexpected error: {}", e);
       Status::failed_precondition("unexpected error")
     }
   }
 }
 
 struct RegistrationResponseAndPakeState {
   response: RegistrationResponse,
   pake_state: ServerRegistration<Cipher>,
 }
 
 struct LoginResponseAndPakeState {
   response: PakeLoginResponseStruct,
   pake_state: ServerLogin<Cipher>,
 }
diff --git a/shared/protos/identity.proto b/shared/protos/identity.proto
index e8121c5f2..b9dd603df 100644
--- a/shared/protos/identity.proto
+++ b/shared/protos/identity.proto
@@ -1,179 +1,202 @@
 syntax = "proto3";
 
 package identity;
 
 service IdentityService {
   // Called by user to register with the Identity Service (PAKE only)
   rpc RegisterUser(stream RegistrationRequest) returns (stream
     RegistrationResponse) {}
   // Called by user to create an active session and get an access token
   rpc LoginUser(stream LoginRequest) returns (stream LoginResponse) {}
   // Called by other services to verify a user's token
   rpc VerifyUserToken(VerifyUserTokenRequest) returns (VerifyUserTokenResponse)
     {}
   // Called by users and keyservers to get userID corresponding to a wallet
   // address or username
   rpc GetUserID(GetUserIDRequest) returns (GetUserIDResponse) {}
 
   rpc DeleteUser(DeleteUserRequest) returns (DeleteUserResponse) {}
   // Called by Ashoat's keyserver with a list of user IDs in MySQL and returns:
   // 1. a list of user IDs that are in DynamoDB but not in the supplied list
   // 2. a list of user IDs that are in the supplied list but not in DynamoDB
   rpc CompareUsers(CompareUsersRequest) returns (CompareUsersResponse) {}
   // Called by clients to get a nonce for a Sign-In with Ethereum message
   rpc GenerateNonce(GenerateNonceRequest) returns (GenerateNonceResponse) {}
+  // Called by clients to get session initialization info needed to open a new
+  // channel of communication with a given user
+  rpc GetSessionInitializationInfo(GetSessionInitializationInfoRequest) returns
+    (GetSessionInitializationInfoResponse) {}
 }
 
 // Helper types
 
 message PakeRegistrationRequestAndUserID {
   string userID = 1;
   // ed25519 key for the given user's device
   string signingPublicKey = 2;
   // Message sent to initiate PAKE registration (step 1)
   bytes pakeRegistrationRequest = 3;
   string username = 4;
 }
 
 message PakeCredentialRequestAndUserID {
   string userID = 1;
   // ed25519 key for the given user's device
   string signingPublicKey = 2;
   // Message sent to initiate PAKE login (step 1)
   bytes pakeCredentialRequest = 3;
 }
 
 message PakeLoginRequest {
   oneof data {
     PakeCredentialRequestAndUserID pakeCredentialRequestAndUserID = 1;
     // Final message in PAKE login (step 3)
     bytes pakeCredentialFinalization = 2;
   }
 }
 
 message PakeLoginResponse {
   oneof data {
     // Answer sent to the user upon reception of the PAKE login attempt,
     // containing a sealed envelope with the user's private key (step 2)
     bytes pakeCredentialResponse = 1;
     string accessToken = 2;
   }
 }
 
 message PakeRegistrationUploadAndCredentialRequest {
   // Final message in PAKE registration, containing sealed cryptographic
   // identifiers (step 3)
   bytes pakeRegistrationUpload = 1;
   // Message sent to initiate PAKE login (Same as in
   // PakeCredentialRequestAndUserID) (step 1)
   bytes pakeCredentialRequest = 2;
 }
 
 message WalletLoginRequest {
   string userID = 1;
   // ed25519 key for the given user's device
   string signingPublicKey = 2;
   string siweMessage = 3;
   bytes siweSignature = 4;
 }
 
 message WalletLoginResponse {
   string accessToken = 1;
 }
 
+message SessionInitializationInfo {
+  // Initially, the key-value pairs will be as follows:
+  // payload -> stringified JSON containing primary and notification public keys
+  // signature -> above payload signed with the signing ed25519 key
+  // socialProof -> a signed message used for SIWE (optional)
+  map<string, string> info = 1;
+}
+
 // RegisterUser
 
 message RegistrationRequest {
   oneof data {
     PakeRegistrationRequestAndUserID pakeRegistrationRequestAndUserID = 1;
     // We combine the last step of PAKE registration with the first step of PAKE
     // login here to reduce the number of messages sent
     PakeRegistrationUploadAndCredentialRequest
       pakeRegistrationUploadAndCredentialRequest = 2;
     // Final message in PAKE login (Same as in PakeLoginRequest) (step 3)
     bytes pakeCredentialFinalization = 3;
   }
 }
 
 message RegistrationResponse {
   oneof data {
     // Answer sent to the user upon reception of the PAKE registration attempt
     // (step 2)
     bytes pakeRegistrationResponse = 1;
     PakeLoginResponse pakeLoginResponse = 2;
   }
 }
 
 // LoginUser
 
 message LoginRequest {
   oneof data {
     PakeLoginRequest pakeLoginRequest = 1;
     WalletLoginRequest walletLoginRequest = 2;
   }
 }
 
 message LoginResponse {
   oneof data {
     PakeLoginResponse pakeLoginResponse = 1;
     WalletLoginResponse walletLoginResponse = 2;
   }
 }
 
 // VerifyUserToken
 
 message VerifyUserTokenRequest {
   string userID = 1;
   // ed25519 key for the given user's device
   string signingPublicKey = 2;
   string accessToken = 3;
 }
 
 message VerifyUserTokenResponse {
   bool tokenValid = 1;
 }
 
 // GetUserID
 
 message GetUserIDRequest {
   enum AuthType {
     PASSWORD = 0;
     WALLET = 1;
   }
   AuthType authType = 1;
   string userInfo = 2;
 }
 
 message GetUserIDResponse {
   string userID = 1;
 }
 
 // DeleteUser
 
 message DeleteUserRequest {
   string userID = 1;
 }
 
 // Need to respond with a message to show success, an
 // empty reponse should work just fine
 message DeleteUserResponse {}
 
 // CompareUsers
 
 message CompareUsersRequest {
   repeated string users = 1;
 }
 
 message CompareUsersResponse {
   repeated string usersMissingFromKeyserver = 1;
   repeated string usersMissingFromIdentity = 2;
 }
 
 // GenerateNonce
 
 message GenerateNonceRequest {
 }
 
 message GenerateNonceResponse{
   string nonce = 1;
 }
+
+// GetSessionInitializationInfo
+
+message GetSessionInitializationInfoRequest {
+  string userID = 1;
+}
+
+message GetSessionInitializationInfoResponse {
+  // Map is keyed on devices' public ed25519 key used for signing
+  map<string, SessionInitializationInfo> devices = 1;
+}