Firefox Send: Send files with end-to-end encryption

I wish Mozilla tools had opportunity to gain more traction, but it would seem the general population of the internet is blind to the fact that Mozilla is not only Firefox and Thunderbird. In fact many people I serviced (personal) computers for called the browser itself Mozilla. On the other hand Firefox is great in that it doesn't push unnecessary widgets on its users. Not even on default Firefox new tab. I guess it's up to users who love Mozilla to promote it.

Anyone know how the encryption is performed?