The 4.16.0 release branch contains a short set of dangerous changes. This release migrates data from the SQLite + ciphertext blobs storage strategy to a SQLCipher + KeyStore storage strategy. That requires a full database scan to move all data from one format to another.

This will open the door to full text message content search, as well as backup. However, I’ve left any positive benefits out of this initial release, so at the moment it is only danger.

If you’d like to help test this migration, you can (hopefully) subscribe to the alpha channel by joining this google group:

https://groups.google.com/forum/#!forum/signal-android-alpha-testers

…and then (I think) updating to the alpha channel from the standard testers URL:

https://play.google.com/apps/testing/org.thoughtcrime.securesms

You should only do this if you’re very brave and want to help at the risk of potentially losing all your Signal data.

Thanks!