Author here. There are other services that do this sort of thing, but none that accomplished all these goals:
1. Browser-encrypted so the server cannot decrypt it. The decryption key is stored in the URL fragment after the # so the server never sees the decryption key. (Fragments are not sent in HTTP requests.)
2. Secrets never touch disk. SneakyNote.com even goes to lengths to clear the in-memory buffers on storage/access.
3. Verified delivery. If you're going to send the link over an insecure channel, you can't prevent someone else from getting to it first. But you'd like to know if they replaced your link. The verification code step solves this problem.
4. Open source.
Incidentally, this is written in Go because it of its good HTTP support and because Go is a memory-safe language that will also allow you to clear memory.
1. Browser-encrypted so the server cannot decrypt it. The decryption key is stored in the URL fragment after the # so the server never sees the decryption key. (Fragments are not sent in HTTP requests.)
2. Secrets never touch disk. SneakyNote.com even goes to lengths to clear the in-memory buffers on storage/access.
3. Verified delivery. If you're going to send the link over an insecure channel, you can't prevent someone else from getting to it first. But you'd like to know if they replaced your link. The verification code step solves this problem.
4. Open source.
Incidentally, this is written in Go because it of its good HTTP support and because Go is a memory-safe language that will also allow you to clear memory.