Using TextSecure

First Run

The first time you run TextSecure, it will ask you to create a passphrase. This passphrase will be used to encrypt all of TextSecure's secret information, including the keys used to encrypt your text messages. The security of your messages depends on the strength of this passphrase, so make it good. TextSecure can be configured to cache this passphrase in memory for as long as its running, or for a specific length of time, so you won't need to be constantly re-entering it in order to access or send messages. This passphrase cannot be recovered if it is lost.

Once TextSecure has been set up, you may wish to disable the default Messaging application. This will prevent problems between the two applications, as well as ensure your SMS and MMS are encrypted upon receipt. To do this, go to Settings > Apps > All > Messaging and click 'Disable'. Reboot your phone to see this take affect.

Secure Storage

All text messages are encrypted with your passphrase before being stored. This encryption includes the bodies of the text messages themselves, but the destination information is currently not encrypted.

Secure Messaging

TextSecure automatically detects when a message is received from another TextSecure user and prompts you to initiate a secure session. If you choose to initiate the secure session, a key exchange will ensue, and a lock icon will be displayed in the title bar of the conversation view as well as on the send button itself. A lock icon will also be displayed next to each encrypted message received, in order to confirm that it was transmitted securely.

Verifying Keys

It is prudent to verify the identity key of conversation's recipient, in order to ensure that no "man in the middle" attack has occurred. From the menu in a conversation, select "Secure Session Options" --> "Verify Recipient Identity." This will present you with an option to manually verify the recipient key's fingerprint, or to verify it by QR code scanning. If you're physically located in the same space as the recipient, you can select QR code scanning to quickly verify each-other's fingerprints. If you're remotely located, you can manually read the fingerprints to each-other over the phone.

Once you verify that the recipient's identity is correct, this information is saved and used to automatically authenticate future secure sessions with that recipient.

Backing Up Messages

Your encrypted messages can be backed up or transferred to a new device by exporting them from the thread list view menu.

Lost Passwords

A lost password cannot be recovered. To continue using TextSecure when a password has been lost the app must be uninstalled and reinstalled, and all messages will be lost.

Quickly Delete All Messages

All messages can be deleted when starting at the conversation list using four steps:

1. Press and hold on any message/conversation
2. In the bottom right, press the "Select All" icon
3. In the bottom left, press the "Delete" icon
4. Press the "Delete" button on the warning dialog box

Secure Push Contacts

Contacts who are able to receive encrypted push TextSecure messages are shown in the "Select Contact" list with a green bar to the left of their name. The green bar indicators will only apply if you are registered for push.