What is URSA?
Consider this scenario: you meet with your friends and agree on a password or secret Key that nobody else knows, and will be changed next time you meet. Then you use it with URSA to encrypt your communications the way encryption has been done for millennia, except that computers make it very fast and secure. Quite old-school in an age of public-key encryption, but people probably will keep on using it long after public-key encryption is gone.
URSA is based on the XSalsa20 stream cipher, by Bernstein et al. This modern, fast cipher has been extensively scrutinized by experts and no weakness has been found.
Messages locked with URSA can be unlocked with PassLok, its more powerful sibling, and vice-versa. This way you can learn to encrypt with URSA, and then graduate to the full range of tools available in PassLok.
You think encryption is hard to use? Not with URSA. You only need to enter the secret Key and the message, and click one button. Putting this on an email or making it undetectable is only one click.
URSA can open real-time chat sessions that include text, files, or even video. Connection is direct between computers or smartphones.
For the paranoid among us, URSA can disguise its encrypted output so it looks like regular text, or even inside images.
It costs us nothing to make URSA available to users, so why not make it free? URSA is a tool for freedom, my friend. And this is not our only free tool. There is also PassLok, mentioned above, and SeeOnce, which makes self-destruct emails and doesn't involve any servers, so your data remains private.