Show HN: Diffie-Hellman exchange for the layman

It bears note that this is still subject to a MITM attack on whatever channel is used for the information exchange. You cannot generate a shared secret without either an existing shared secret or some form of secure authenticated communication channel in the first place. I mean, you can, but you can't be sure who it is that you're sharing the new secret with.

diffie-hellman key change for anyone:<p>given large prime p, some a, some b:<p>1. A = g^a mod p<p>2. B = g^b mod p<p>3. exchange A,B<p>4. B^a mod p = (g^b)^a mod p = (g^a)^b mod p = A^b mod p is the shared key.<p>the end

Interesting, but why does the &quot;Check&quot; use a handmade hashing algorithm that is just summing up all bytes?<p>A much safer implementation would be to take the sha256 of the key and only show the 2 rightmost bytes.

I&#x27;ve improved the encrypt&#x2F;decrypt form. Now the textareas expand, and there&#x27;s a copy to clipboard button in order to copy the output. It makes it much easier to use on the phone.

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

This is really great! I liked the video explanation as well as the page which shows how we go about exchanging information using DH exchange. Will be sharing this page with some of my non-technical friends.<p>Thank you!

Note: P-256 is not considered a safe curve. Use Curve25519 instead. See: <a href="https:&#x2F;&#x2F;safecurves.cr.yp.to&#x2F;" rel="nofollow">https:&#x2F;&#x2F;safecurves.cr.yp.to&#x2F;</a>

I&#x27;ve made a new addition: now the operating system of the other party is also sent as part of the exchange. This info helps decide what software to use for further encryption. e.g. DMG or BitLocker? And, I managed to do it without making the string longer. I stuffed it in the unused bits of the compressed coordinate.

I&#x27;ve simplified the page by creating two modes: &quot;simple&quot; and &quot;advanced&quot;. By default &quot;simple&quot; is shown, and it&#x27;s what you&#x27;d need if you are the recipient, rather than initiator.

IIRC, aren&#x27;t there a bazillion gotchas and practical problems implementing DH where it&#x27;s definitely something one shouldn&#x27;t roll their own?

cant help but be distracted by there being a circular picture of the author staring at me as i read this

Only thing I would improve on this page is to remove all remote dependencies, youtube, font, cdn files ... sw.js consonantly sending some data. Personally I do not trust Google they have way to more data, and even if all scripts are stripped questions is does Chrome collecting data as well?