Locked SMS is an application that allows you to encrypt your SMS/text messages to anyone. Normal SMS messages are set over the communication channel in plain text. Thus, subject to potential exposure of you messages to anyone "listening" on the channel.

Locked SMS uses hybrid encryption with both RSA and AES algorithms. This is the "gold standard" for secure communication. It allows for high speed symmetric encryption with AES and key-distribution safety of asymmetric encryption.

You can choose whether or not to encrypt your messages. The control of this is completely on the user. The encryption requires a key exchange between users if you want to use hybrid encryption. This involves sharing a public key. However, no one can perform decryption with only the public key. The secret key is kept secure on the phone. Your messages are not accessible to anyone except the owner of the phone. When receiving an encrypted message, it is up to the user to leave it encrypted or not after decrypting and reading the message (messages can also be completely deleted). Also, none of the user data is stored or seen anywhere else. There is no backup of any information (ie: on Google) and no data is cached or stored anywhere where else. Hourglass Software does not store any data or has access to any of the data.

In the end, the user has full autonomy of your SMS communication privacy.
You can also choose to have Locked SMS be your primary/default SMS application or secondary alongside the phone's existing SMS application.

Instructions to use Encryption feature:
1. User A goes to "New Conversation" screen (plus button at bottom right)
2. Enter User B phone number
3. Click "Send Key"
4. User B gets SMS message with link
5. User B clicks link in SMS to save key
6. User B does the same steps to send key to User A to save
7. Both users can now choose to encrypt messages to each other
(Same process for using encryption for other users/contacts)