diff --git a/.eslintignore b/.eslintignore
index aa9a74971d3f..ff968ce0e947 100644
--- a/.eslintignore
+++ b/.eslintignore
@@ -12,6 +12,7 @@ test/views/*.js
 # Generated files
 js/components.js
 js/libtextsecure.js
+js/util_worker.js
 js/libsignal-protocol-worker.js
 libtextsecure/components.js
 libtextsecure/test/test.js
diff --git a/.gitignore b/.gitignore
index 3ee9ea879dd7..b1b7020d175b 100644
--- a/.gitignore
+++ b/.gitignore
@@ -17,6 +17,7 @@ sql/
 
 # generated files
 js/components.js
+js/util_worker.js
 js/libtextsecure.js
 libtextsecure/components.js
 libtextsecure/test/test.js
diff --git a/.prettierignore b/.prettierignore
index 21047597f8f8..0b44d051edeb 100644
--- a/.prettierignore
+++ b/.prettierignore
@@ -6,6 +6,7 @@ config/local-*.json
 config/local.json
 dist/**
 js/components.js
+js/util_worker.js
 js/libtextsecure.js
 libtextsecure/components.js
 libtextsecure/test/test.js
diff --git a/Gruntfile.js b/Gruntfile.js
index 355d4add7702..30f2259f27d4 100644
--- a/Gruntfile.js
+++ b/Gruntfile.js
@@ -33,6 +33,14 @@ module.exports = grunt => {
         src: components,
         dest: 'js/components.js',
       },
+      util_worker: {
+        src: [
+          'components/bytebuffer/dist/ByteBufferAB.js',
+          'components/long/dist/Long.js',
+          'js/util_worker_tasks.js',
+        ],
+        dest: 'js/util_worker.js',
+      },
       libtextsecurecomponents: {
         src: libtextsecurecomponents,
         dest: 'libtextsecure/components.js',
diff --git a/js/modules/data.js b/js/modules/data.js
index 31b41b4add5c..ff3c996e7e59 100644
--- a/js/modules/data.js
+++ b/js/modules/data.js
@@ -166,7 +166,7 @@ ipcRenderer.on(
     const job = _getJob(jobId);
     if (!job) {
       throw new Error(
-        `Received job reply to job ${jobId}, but did not have it in our registry!`
+        `Received SQL channel reply to job ${jobId}, but did not have it in our registry!`
       );
     }
 
@@ -174,7 +174,9 @@ ipcRenderer.on(
 
     if (errorForDisplay) {
       return reject(
-        new Error(`Error calling channel ${fnName}: ${errorForDisplay}`)
+        new Error(
+          `Error received from SQL channel job ${jobId} (${fnName}): ${errorForDisplay}`
+        )
       );
     }
 
@@ -196,7 +198,8 @@ function makeChannel(fnName) {
       });
 
       setTimeout(
-        () => reject(new Error(`Request to ${fnName} timed out`)),
+        () =>
+          reject(new Error(`SQL channel job ${jobId} (${fnName}) timed out`)),
         DATABASE_UPDATE_TIMEOUT
       );
     });
diff --git a/js/util_worker_tasks.js b/js/util_worker_tasks.js
new file mode 100644
index 000000000000..4d6c80bda066
--- /dev/null
+++ b/js/util_worker_tasks.js
@@ -0,0 +1,44 @@
+/* global dcodeIO */
+/* eslint-disable strict */
+
+'use strict';
+
+const functions = {
+  stringToArrayBufferBase64,
+  arrayBufferToStringBase64,
+};
+
+onmessage = async e => {
+  const [jobId, fnName, ...args] = e.data;
+
+  try {
+    const fn = functions[fnName];
+    if (!fn) {
+      throw new Error(`Worker: job ${jobId} did not find function ${fnName}`);
+    }
+    const result = await fn(...args);
+    postMessage([jobId, null, result]);
+  } catch (error) {
+    const errorForDisplay = prepareErrorForPostMessage(error);
+    postMessage([jobId, errorForDisplay]);
+  }
+};
+
+function prepareErrorForPostMessage(error) {
+  if (!error) {
+    return null;
+  }
+
+  if (error.stack) {
+    return error.stack;
+  }
+
+  return error.message;
+}
+
+function stringToArrayBufferBase64(string) {
+  return dcodeIO.ByteBuffer.wrap(string, 'base64').toArrayBuffer();
+}
+function arrayBufferToStringBase64(arrayBuffer) {
+  return dcodeIO.ByteBuffer.wrap(arrayBuffer).toString('base64');
+}
diff --git a/libtextsecure/message_receiver.js b/libtextsecure/message_receiver.js
index ba9eb66afd74..e0a2c7ad7cb7 100644
--- a/libtextsecure/message_receiver.js
+++ b/libtextsecure/message_receiver.js
@@ -9,9 +9,112 @@
 /* global _: false */
 /* global ContactBuffer: false */
 /* global GroupBuffer: false */
+/* global Worker: false */
 
 /* eslint-disable more/no-then */
 
+const WORKER_TIMEOUT = 60 * 1000; // one minute
+
+const _utilWorker = new Worker('js/util_worker.js');
+const _jobs = Object.create(null);
+const _DEBUG = false;
+let _jobCounter = 0;
+
+function _makeJob(fnName) {
+  _jobCounter += 1;
+  const id = _jobCounter;
+
+  if (_DEBUG) {
+    window.log.info(`Worker job ${id} (${fnName}) started`);
+  }
+  _jobs[id] = {
+    fnName,
+    start: Date.now(),
+  };
+
+  return id;
+}
+
+function _updateJob(id, data) {
+  const { resolve, reject } = data;
+  const { fnName, start } = _jobs[id];
+
+  _jobs[id] = {
+    ..._jobs[id],
+    ...data,
+    resolve: value => {
+      _removeJob(id);
+      const end = Date.now();
+      window.log.info(
+        `Worker job ${id} (${fnName}) succeeded in ${end - start}ms`
+      );
+      return resolve(value);
+    },
+    reject: error => {
+      _removeJob(id);
+      const end = Date.now();
+      window.log.info(
+        `Worker job ${id} (${fnName}) failed in ${end - start}ms`
+      );
+      return reject(error);
+    },
+  };
+}
+
+function _removeJob(id) {
+  if (_DEBUG) {
+    _jobs[id].complete = true;
+  } else {
+    delete _jobs[id];
+  }
+}
+
+function _getJob(id) {
+  return _jobs[id];
+}
+
+async function callWorker(fnName, ...args) {
+  const jobId = _makeJob(fnName);
+
+  return new Promise((resolve, reject) => {
+    _utilWorker.postMessage([jobId, fnName, ...args]);
+
+    _updateJob(jobId, {
+      resolve,
+      reject,
+      args: _DEBUG ? args : null,
+    });
+
+    setTimeout(
+      () => reject(new Error(`Worker job ${jobId} (${fnName}) timed out`)),
+      WORKER_TIMEOUT
+    );
+  });
+}
+
+_utilWorker.onmessage = e => {
+  const [jobId, errorForDisplay, result] = e.data;
+
+  const job = _getJob(jobId);
+  if (!job) {
+    throw new Error(
+      `Received worker reply to job ${jobId}, but did not have it in our registry!`
+    );
+  }
+
+  const { resolve, reject, fnName } = job;
+
+  if (errorForDisplay) {
+    return reject(
+      new Error(
+        `Error received from worker job ${jobId} (${fnName}): ${errorForDisplay}`
+      )
+    );
+  }
+
+  return resolve(result);
+};
+
 function MessageReceiver(username, password, signalingKey, options = {}) {
   this.count = 0;
 
@@ -35,10 +138,11 @@ MessageReceiver.stringToArrayBuffer = string =>
   Promise.resolve(dcodeIO.ByteBuffer.wrap(string, 'binary').toArrayBuffer());
 MessageReceiver.arrayBufferToString = arrayBuffer =>
   Promise.resolve(dcodeIO.ByteBuffer.wrap(arrayBuffer).toString('binary'));
+
 MessageReceiver.stringToArrayBufferBase64 = string =>
-  Promise.resolve(dcodeIO.ByteBuffer.wrap(string, 'base64').toArrayBuffer());
+  callWorker('stringToArrayBufferBase64', string);
 MessageReceiver.arrayBufferToStringBase64 = arrayBuffer =>
-  Promise.resolve(dcodeIO.ByteBuffer.wrap(arrayBuffer).toString('base64'));
+  callWorker('arrayBufferToStringBase64', arrayBuffer);
 
 MessageReceiver.prototype = new textsecure.EventTarget();
 MessageReceiver.prototype.extend({