Twitter releases TextSecure

It's for 2 secure platforms separated by insecure infrastructure to communicate securely despite the insecurity in the infrastructure between them.

For example, if we can do encryption in our head, we can talk safely despite the fact that talk can be intercepted by a nearby microphone - but this only works because our platforms (brain) is secure.

Similarily, I can encrypt an email and send it trough the insecure internet - but this only works aslong as the platforms doing encryption and decryption are secure.

Encryption can't solve the problem of the platform being used to do the crypto itself, being insecure.