Cipher for iMessage lets you send secret and digitally signed messages with Touch ID.
Now you have an easy way of sharing secret information (like passwords, phone numbers, etc). The recipient of your message will be asked to authenticate using Touch ID (or device passcode), thus ensuring that only the device owner will see your message.
You can also use Cipher to digitally sign your message with Touch ID. A digital signature assures the recipient that the message indeed came from you, because you authenticated with Touch ID (or device passcode).
The free version of Cipher enables you to view secret and digitally signed messages you receive. Upgrade to Pro via the in-app purchase to unlock sending secret and signed messages.