diff --git a/config/default.json b/config/default.json
index 31462adf2..ee40150e8 100644
--- a/config/default.json
+++ b/config/default.json
@@ -31,5 +31,6 @@
     "-----BEGIN CERTIFICATE-----\nMIID7zCCAtegAwIBAgIJAIm6LatK5PNiMA0GCSqGSIb3DQEBBQUAMIGNMQswCQYD\nVQQGEwJVUzETMBEGA1UECAwKQ2FsaWZvcm5pYTEWMBQGA1UEBwwNU2FuIEZyYW5j\naXNjbzEdMBsGA1UECgwUT3BlbiBXaGlzcGVyIFN5c3RlbXMxHTAbBgNVBAsMFE9w\nZW4gV2hpc3BlciBTeXN0ZW1zMRMwEQYDVQQDDApUZXh0U2VjdXJlMB4XDTEzMDMy\nNTIyMTgzNVoXDTIzMDMyMzIyMTgzNVowgY0xCzAJBgNVBAYTAlVTMRMwEQYDVQQI\nDApDYWxpZm9ybmlhMRYwFAYDVQQHDA1TYW4gRnJhbmNpc2NvMR0wGwYDVQQKDBRP\ncGVuIFdoaXNwZXIgU3lzdGVtczEdMBsGA1UECwwUT3BlbiBXaGlzcGVyIFN5c3Rl\nbXMxEzARBgNVBAMMClRleHRTZWN1cmUwggEiMA0GCSqGSIb3DQEBAQUAA4IBDwAw\nggEKAoIBAQDBSWBpOCBDF0i4q2d4jAXkSXUGpbeWugVPQCjaL6qD9QDOxeW1afvf\nPo863i6Crq1KDxHpB36EwzVcjwLkFTIMeo7t9s1FQolAt3mErV2U0vie6Ves+yj6\ngrSfxwIDAcdsKmI0a1SQCZlr3Q1tcHAkAKFRxYNawADyps5B+Zmqcgf653TXS5/0\nIPPQLocLn8GWLwOYNnYfBvILKDMItmZTtEbucdigxEA9mfIvvHADEbteLtVgwBm9\nR5vVvtwrD6CCxI3pgH7EH7kMP0Od93wLisvn1yhHY7FuYlrkYqdkMvWUrKoASVw4\njb69vaeJCUdU+HCoXOSP1PQcL6WenNCHAgMBAAGjUDBOMB0GA1UdDgQWBBQBixjx\nP/s5GURuhYa+lGUypzI8kDAfBgNVHSMEGDAWgBQBixjxP/s5GURuhYa+lGUypzI8\nkDAMBgNVHRMEBTADAQH/MA0GCSqGSIb3DQEBBQUAA4IBAQB+Hr4hC56m0LvJAu1R\nK6NuPDbTMEN7/jMojFHxH4P3XPFfupjR+bkDq0pPOU6JjIxnrD1XD/EVmTTaTVY5\niOheyv7UzJOefb2pLOc9qsuvI4fnaESh9bhzln+LXxtCrRPGhkxA1IMIo3J/s2WF\n/KVYZyciu6b4ubJ91XPAuBNZwImug7/srWvbpk0hq6A6z140WTVSKtJG7EP41kJe\n/oF4usY5J7LPkxK3LWzMJnb5EIJDmRvyH8pyRwWg6Qm6qiGFaI4nL8QU4La1x2en\n4DGXRaLMPRwjELNgQPodR38zoCMuA8gHZfZYYoZ7D7Q1wNUiVHcxuFrEeBaYJbLE\nrwLV\n-----END CERTIFICATE-----\n",
   "import": false,
   "serverTrustRoot": "BbqY1DzohE4NUZoVF+L18oUPrK3kILllLEJh2UnPSsEx",
-  "defaultPublicChatServer": "https://chat.lokinet.org/"
+  "defaultPublicChatServer": "https://chat.lokinet.org/",
+  "defaultFileServer": "https://file.lokinet.org"
 }
diff --git a/js/background.js b/js/background.js
index 5e656247c..3f6e34673 100644
--- a/js/background.js
+++ b/js/background.js
@@ -229,7 +229,10 @@
     const ourKey = textsecure.storage.user.getNumber();
     window.feeds = [];
     window.lokiMessageAPI = new window.LokiMessageAPI(ourKey);
+    // singleton to relay events to libtextsecure/message_receiver
     window.lokiPublicChatAPI = new window.LokiPublicChatAPI(ourKey);
+    // singleton to interface the File server
+    window.lokiFileServerAPI = new window.LokiFileServerAPI(ourKey);
     window.lokiP2pAPI = new window.LokiP2pAPI(ourKey);
     window.lokiP2pAPI.on('pingContact', pubKey => {
       const isPing = true;
diff --git a/js/modules/loki_file_server_api.js b/js/modules/loki_file_server_api.js
new file mode 100644
index 000000000..a07d20f5d
--- /dev/null
+++ b/js/modules/loki_file_server_api.js
@@ -0,0 +1,40 @@
+/* global storage: false */
+/* global libloki: false */
+/* global Signal: false */
+
+const LokiAppDotNetAPI = require('./loki_app_dot_net_api');
+
+const DEVICE_MAPPING_ANNOTATION_KEY = 'network.loki.messenger.devicemapping';
+
+// returns the LokiFileServerAPI constructor with the serverUrl already consumed
+function LokiFileServerAPIWrapper(serverUrl) {
+  return LokiFileServerAPI.bind(null, serverUrl);
+}
+
+class LokiFileServerAPI {
+  constructor(serverUrl, ourKey) {
+    this.ourKey = ourKey;
+    this._adnApi = new LokiAppDotNetAPI(ourKey);
+    this._server = this._adnApi.findOrCreateServer(serverUrl);
+  }
+
+  async getUserDeviceMapping(pubKey) {
+    const annotations = await this._server.getUserAnnotations(pubKey);
+    return annotations.find(
+      annotation => annotation.type === DEVICE_MAPPING_ANNOTATION_KEY
+    );
+  }
+
+  setOurDeviceMapping(authorisations, isPrimary) {
+    const content = {
+      isPrimary: isPrimary ? '1' : '0',
+      authorisations,
+    };
+    return this._server.setSelfAnnotation(
+      DEVICE_MAPPING_ANNOTATION_KEY,
+      content
+    );
+  }
+}
+
+module.exports = LokiFileServerAPIWrapper;
diff --git a/main.js b/main.js
index 8b545fafc..f5e608004 100644
--- a/main.js
+++ b/main.js
@@ -166,6 +166,7 @@ function prepareURL(pathSegments, moreKeys) {
       contentProxyUrl: config.contentProxyUrl,
       importMode: importMode ? true : undefined, // for stringify()
       serverTrustRoot: config.get('serverTrustRoot'),
+      defaultFileServer: config.get('defaultFileServer'),
       ...moreKeys,
     },
   });
diff --git a/preload.js b/preload.js
index fc5b12ca0..39ffb5bc2 100644
--- a/preload.js
+++ b/preload.js
@@ -326,6 +326,11 @@ window.LokiMessageAPI = require('./js/modules/loki_message_api');
 
 window.LokiPublicChatAPI = require('./js/modules/loki_public_chat_api');
 
+const LokiFileServerAPIWrapper = require('./js/modules/loki_file_server_api');
+
+// bind first argument as we have it here already
+window.LokiFileServerAPI = LokiFileServerAPIWrapper(config.defaultFileServer);
+
 window.LokiRssAPI = require('./js/modules/loki_rss_api');
 
 window.LocalLokiServer = require('./libloki/modules/local_loki_server');