boris1

I've now implemented folder encryption. If you encrypt folder 'foo', you get the file 'foo.encrypted'. When you decrypt it using the same tool, you get file 'foo.zip' which you download and uncompress into a folder 'foo'.

Update: the tool now allows to encrypt (and decrypt) files. It works in mobile browser too.

The check digits solve the MITM problem. You should compare them by another channel than email, such as text message. This is called "Short Authentication String" (SAS).

Thanks, gonna fix it.

I've improved the encrypt/decrypt form. Now the textareas expand, and there's a copy to clipboard button in order to copy the output. It makes it much easier to use on the phone.

Yes, just do not write (mod p), as it can be misleading to the reader. A mathematician doesn't care, but in RFCs they call the (mod p) groups a "prime group" to differentiate it from the Elliptic Curve group. (In fact, I think they call them "prime fields", not merely groups).

I think the keys can be smaller because every random coordinate is a valid value (valid key), but in the case of RSA, valid values are more sparse.

I'm using Elliptic Curve variant. There's no "mod". But you got the general idea. Also, all the math is built-in and done natively by the browser.

The only way is to use another channel for the Short Authentication String (SAS) (check digits in my case). I recommend that people SMS them the check digits, and exchange the DH offers by email.

There's no difference for the MITM how I pick the Short Authentication String (SAS) (the check digits).

But there's a difference in terms of strength of the encryption key, if you are planning to use the full password as input to Key Derivation Function (KDF). If you make public the first 5 letters of a 44 letter password, you've just made lost some of the entropy.

By the way, based on a comment in this thread, I added a SHA-256 stage. I now hash the full password, and sum the bytes of the hash to generate the check digits.

I've simplified the page by creating two modes: "simple" and "advanced". By default "simple" is shown, and it's what you'd need if you are the recipient, rather than an initiator would would be normally more technical.

I've simplified the page by creating two modes: "simple" and "advanced". By default "simple" is shown, and it's what you'd need if you are the recipient, rather than initiator.