SeeOnce encrypts your email messages so that they can be decrypted only once by the intended recipient and after that nobody can decrypt them again. It does this without involving any servers or forcing you to make an account anywhere. You can keep using your preferred email.
Many other apps and extensions store your private content somewhere. SeeOnce does not do this; instead, it achieves forward secrecy by changing encryption keys with every message. This way, you dont have to trust anybody. Not even SeeOnce.
When you get a SeeOnce-locked message, just copy it into SeeOnce and it will open automatically. Then you can reply directly from SeeOnce.
Your friends dont need to have the SeeOnce app. Messages open in a webpage just by clicking them. They can do this on a smartphone or on a PC. They dont need to be online.
Some people live in places where using encryption is itself compromising. This is why SeeOnce can disguise its output so it looks like normal text. Just supply a sufficiently long cover text after the message is locked. Disguised messages also unlock as soon as you paste them into SeeOnce.
SeeOnce has comprehensive help just one click away.
SeeOnce uses 255-bit standard elliptic curves, which have been vetted against weaknesses by experts. On top of that, SeeOnce uses 256-bit XSalsa20 encryption and 512-bit hash functions to complete the locking process. XSalsa20 is a high-performance, open source cipher, which has been scrutinized by experts for nearly a decade without any practical weaknesses being found.
This is the iOS version of SeeOnce, essentially identical to the web version. The following is to check the authenticity of the web version of SeeOnce:
Current version of SeeOnce is: 1.0.2
Made on 10/31/15
Main source: https://seeonce.net
SHA256 string for web source (single html file):
7213-eb62-fb04-b14e-44a4-74af-1b84-a1d9-a5f3-4e85-0eac-fa59-9337-db8d-57a5-0670
Watch F. Ruiz reading this string:
https://www.youtube.com/watch?v=49ZoiTPxRWk