diff -r 000000000000 -r 6474c204b198 mobile/android/base/sync/crypto/PersistedCrypto5Keys.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mobile/android/base/sync/crypto/PersistedCrypto5Keys.java	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,103 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+package org.mozilla.gecko.sync.crypto;
+
+import org.mozilla.gecko.background.common.log.Logger;
+import org.mozilla.gecko.sync.CollectionKeys;
+import org.mozilla.gecko.sync.CryptoRecord;
+
+import android.content.SharedPreferences;
+
+public class PersistedCrypto5Keys {
+  public static final String LOG_TAG = "PersistedC5Keys";
+
+  public static final String CRYPTO5_KEYS_SERVER_RESPONSE_BODY = "crypto5KeysServerResponseBody";
+  public static final String CRYPTO5_KEYS_LAST_MODIFIED        = "crypto5KeysLastModified";
+
+  protected SharedPreferences prefs;
+  protected KeyBundle syncKeyBundle;
+
+  public PersistedCrypto5Keys(SharedPreferences prefs, KeyBundle syncKeyBundle) {
+    if (syncKeyBundle == null) {
+      throw new IllegalArgumentException("Null syncKeyBundle passed in to PersistedCrypto5Keys constructor.");
+    }
+    this.prefs = prefs;
+    this.syncKeyBundle = syncKeyBundle;
+  }
+
+  /**
+   * Get persisted crypto/keys.
+   * <p>
+   * crypto/keys is fetched from an encrypted JSON-encoded <code>CryptoRecord</code>.
+   *
+   * @return A <code>CollectionKeys</code> instance or <code>null</code> if none
+   *         is currently persisted.
+   */
+  public CollectionKeys keys() {
+    String keysJSON = prefs.getString(CRYPTO5_KEYS_SERVER_RESPONSE_BODY, null);
+    if (keysJSON == null) {
+      return null;
+    }
+    try {
+      CryptoRecord cryptoRecord = CryptoRecord.fromJSONRecord(keysJSON);
+      CollectionKeys keys = new CollectionKeys();
+      keys.setKeyPairsFromWBO(cryptoRecord, syncKeyBundle);
+      return keys;
+    } catch (Exception e) {
+      Logger.warn(LOG_TAG, "Got exception decrypting persisted crypto/keys.", e);
+      return null;
+    }
+  }
+
+  /**
+   * Persist crypto/keys.
+   * <p>
+   * crypto/keys is stored as an encrypted JSON-encoded <code>CryptoRecord</code>.
+   *
+   * @param keys
+   *          The <code>CollectionKeys</code> object to persist, which should
+   *          have the same default key bundle as the sync key bundle.
+   */
+  public void persistKeys(CollectionKeys keys) {
+    if (keys == null) {
+      Logger.debug(LOG_TAG, "Clearing persisted crypto/keys.");
+      prefs.edit().remove(CRYPTO5_KEYS_SERVER_RESPONSE_BODY).commit();
+      return;
+    }
+    try {
+      CryptoRecord cryptoRecord = keys.asCryptoRecord();
+      cryptoRecord.keyBundle = syncKeyBundle;
+      cryptoRecord.encrypt();
+      String keysJSON = cryptoRecord.toJSONString();
+      Logger.debug(LOG_TAG, "Persisting crypto/keys.");
+      prefs.edit().putString(CRYPTO5_KEYS_SERVER_RESPONSE_BODY, keysJSON).commit();
+    } catch (Exception e) {
+      Logger.warn(LOG_TAG, "Got exception encrypting while persisting crypto/keys.", e);
+    }
+  }
+
+  public boolean persistedKeysExist() {
+    return lastModified() > 0;
+  }
+
+  public long lastModified() {
+    return prefs.getLong(CRYPTO5_KEYS_LAST_MODIFIED, -1);
+  }
+
+  public void persistLastModified(long lastModified) {
+    if (lastModified <= 0) {
+      Logger.debug(LOG_TAG, "Clearing persisted crypto/keys last modified timestamp.");
+      prefs.edit().remove(CRYPTO5_KEYS_LAST_MODIFIED).commit();
+      return;
+    }
+    Logger.debug(LOG_TAG, "Persisting crypto/keys last modified timestamp " + lastModified + ".");
+    prefs.edit().putLong(CRYPTO5_KEYS_LAST_MODIFIED, lastModified).commit();
+  }
+
+  public void purge() {
+    persistLastModified(-1);
+    persistKeys(null);
+  }
+}