> neither party will have any desire to do something underhanded like recording the video from another phone.
Well... The viewer needs to request permission from the partner, and may want to bypass that. Furthermore, a given video may have more than two partecipants, and the app seems to be limited to pairs of people. In such situations the video will need to be shared with those people too.
The most secure option is to have one encrypted copy of the file and only that, and decrypt only when viewing it, and only temporarily. Even then it's possible to make recordings of the content as tiny hideable cameras are sold everywhere. I'm not dismissing the work done, but if someone is as careful about security to use such an app, they can also do the best thing and not record at all.
Well... The viewer needs to request permission from the partner, and may want to bypass that. Furthermore, a given video may have more than two partecipants, and the app seems to be limited to pairs of people. In such situations the video will need to be shared with those people too.
The most secure option is to have one encrypted copy of the file and only that, and decrypt only when viewing it, and only temporarily. Even then it's possible to make recordings of the content as tiny hideable cameras are sold everywhere. I'm not dismissing the work done, but if someone is as careful about security to use such an app, they can also do the best thing and not record at all.