Show HN: Get encrypted data from people that don’t know how to encrypt • Hacker News Board

Re: Show HN: Get encrypted data from people that don’t know how to encrypt

#31

Post by dkopi » Wed, Oct 19, 2016, 11:42 AM UTC

The weakest link I can identify here is MITM attacks when you're sending the link.

Imagine:

  Alice generates a link. 
  Sends the link to Bob over an unencrypted/unauthenticated link.
  Mallory intercepts the link. Generates his own link and send that link to bob.
  Bob enters the confidential information on Mallory's link.
  Mallory sees the confidential information, and then sends it to Alice's original link.

The only way to prevent this type of attack is sending the link over a secure channel. But if you already have a secure channel - what's the use case?

Re: Show HN: Get encrypted data from people that don’t know how to encrypt

#32

Post by dethos » Wed, Oct 19, 2016, 11:45 AM UTC

erikb wrote: post #18

If you can get the library to the sender's browser without security problems then it probably can securely encrypt the text and send it to the target. But is it always secure to send someone the library that you want to use?

Your point is valid and the project should always run through HTTPS (with HSTS). All assets are served from the local server.

Re: Show HN: Get encrypted data from people that don’t know how to encrypt

#33

Post by [deleted] » Wed, Oct 19, 2016, 11:48 AM UTC

dkopi wrote: post #31

The weakest link I can identify here is MITM attacks when you're sending the link. Imagine: Alice generates a link. Sends the link to Bob over an unencrypted/unauthenticated link. Mallory intercepts the link. Generates his own link and send that link to bob. Bob enters the confidential information on Mallory's link. Mallory sees the confidential information, and then sends it to Alice's original link. The only way to…

[deleted]

Re: Show HN: Get encrypted data from people that don’t know how to encrypt

#34

Post by dethos » Wed, Oct 19, 2016, 11:52 AM UTC

ComodoHacker wrote: post #9

How is this different from e2e-encrypted webchat?

Nothing is stored and probably the most relevant difference is the medium, you might not have those contacts in a secure e2e encrypted chat (probably they only use skype), but almost everyone uses email.

Re: Show HN: Get encrypted data from people that don’t know how to encrypt

#35

Post by rhaps0dy » Wed, Oct 19, 2016, 12:03 PM UTC

dkopi wrote: post #31

The weakest link I can identify here is MITM attacks when you're sending the link. Imagine: Alice generates a link. Sends the link to Bob over an unencrypted/unauthenticated link. Mallory intercepts the link. Generates his own link and send that link to bob. Bob enters the confidential information on Mallory's link. Mallory sees the confidential information, and then sends it to Alice's original link. The only way to…

>But if you already have a secure channel - what's the use case?

You can use Whatsapp, or some other E2E-encrypted service that is easy to use, and then transmit the sensitive data over encrypted email, which is more convenient for long-form text.

Re: Show HN: Get encrypted data from people that don’t know how to encrypt

#36

Post by arnoxmp » Wed, Oct 19, 2016, 12:14 PM UTC

Like several others I made a similar tool years ago : https://transfer.pw/

It uses client side encryption, dyn. created keys, and the message is deleted after first retrieval.

A slightly different usecase than the OP, still using it for all my clients.

Re: Show HN: Get encrypted data from people that don’t know how to encrypt

#37

Post by dethos » Wed, Oct 19, 2016, 12:14 PM UTC

dkopi wrote: post #31

The weakest link I can identify here is MITM attacks when you're sending the link. Imagine: Alice generates a link. Sends the link to Bob over an unencrypted/unauthenticated link. Mallory intercepts the link. Generates his own link and send that link to bob. Bob enters the confidential information on Mallory's link. Mallory sees the confidential information, and then sends it to Alice's original link. The only way to…

You are right on this one. The only protection against this situation implemented (right now), is that the email address to where it will be sent and the fingerprint of the key that will be used to encrypt, are shown to the user of the link so he is able to verify it. This way mallory's email address will show up on the page and the user can see he is not be sending to the right person.

This might not be enough for the app use cases, but we are working on more solutions so the user can be sure that it is going to the right person.

Regarding the last statement, lets assume the "secure" channel they have is chat app, like slack, for example, it will store the content indefinitely and will be there in clear text, not only slack can see it but if a smartphone/computer is lost,stolen or accessed by someone else they will be able to see all history and content sent through it.

Re: Show HN: Get encrypted data from people that don’t know how to encrypt

#38

Post by martin-adams » Wed, Oct 19, 2016, 12:20 PM UTC

smnscu wrote: post #22

StavrosK wrote: post #13

Earlier quoted context omitted.

He's saying that, even though he changed the message, the signature still validated. He doesn't realize that the resulting GPG file contains the message, so it's verifying it against its own, stored copy.

This reminds me of Craig Wright's blog post where he "proved" he is Satoshi, albeit that one was deliberately misleading. Off-topic, I think in addressing people with 'they' is more polite when the gender is ambiguous, despite the stats being in your favour.

Funny you mention 'they'. I usually do that but noticed in one of my replies I used 'he'. Turns out I reciprocate what other's say without thinking about it.

Re: Show HN: Get encrypted data from people that don’t know how to encrypt

#39

Post by dvh » Wed, Oct 19, 2016, 12:24 PM UTC

Freak_NL wrote: post #25

StavrosK wrote: post #13

Earlier quoted context omitted.

He's saying that, even though he changed the message, the signature still validated. He doesn't realize that the resulting GPG file contains the message, so it's verifying it against its own, stored copy.

I think dvh is confused about detached signatures and signatures that contain their payload. For detached signatures: gpg --verify message.sig message For signed files: gpg --verify message.sig gpg --output message --decrypt message.sig It's all documented¹. Dvh: what are you getting at? 1: https://www.gnupg.org/gph/en/manual/x135.html

I'm just trying to point out that it is easy to make mistake by checking normal signature and detached signature.

Re: Show HN: Get encrypted data from people that don’t know how to encrypt

#40

Post by StavrosK » Wed, Oct 19, 2016, 12:28 PM UTC

eli wrote: post #24

StavrosK wrote: post #14

Earlier quoted context omitted.

SRI is a great way to make an html page that loads all the js from a server, tell the user to store that locally, and be sure that the loaded js files will never change (otherwise they won't get loaded).

Why not just store all the js locally too?

Purely for UX, it's easier to say "save the page you're currently viewing" than "save this page and also these files". It's not a huge difference, though, as you noted.