How does encrypt.to ensure correctness?

[devurandom]

It seems to me that encrypt.to could be DoSed for certain addresses by adding fake keys for that address into the web-of-trust.

Assume A has a key 0xA for his email address a@a in the web-of-trust. Now E wants to DoS encrypt.to for him - he adds a key 0xE for the same email address a@a.

How does encrypt.to decide which key to use for encryption?

In case there is no solution implemented, I would suggest to allow the user to define entry points into the web-of-trust - i.e. keys he trusts. This should reduce the chance for conflicts (but does not make them impossible!). This, of course, complicates the whole system.

Maybe it can be coupled with a social network, like Diaspora.

[wiegelmann]

In that case E can't read A emails, how should E reads A encrypted message?

[devurandom]

The issue is that A cannot read his emails, either. The attack is not MitM or similar, but DoS.

[xaionaro]

I think, that recipients should be able to control pubkeys to be used to encrypt letters to them.

Sorry for my lame English. :)

[wiegelmann]

@xaionaro That's possible, just sign up and upload your prefered public key.

[xaionaro]

Button "Create an account" is unclickable on page "https://encrypt.to/users/sign_up". All fields are filled. Browser "Opera 12.16".

[wiegelmann]

Did you see the green message: "Public key is valid."? Works with Opera 18.0.1284.68.

[xaionaro]

No, I don't see any messages about pubkey validness. Let me try another browser.

I other browser I see "Sorry the public key is invalid. Try again!". But what's wrong in my pubkey? Is there howto to export with "gpg" anywhere? I've used:

gpg --export 8E30679C | base64

[wiegelmann]

Not base64 - export the key:

gpg -a --output gpg-key.asc --export 8E30679C

[xaionaro]

@wiegelmann, thanks, works.

@devurandom, I don't see any problem, if recipients are able to setup pubkeys to use. :)

[wiegelmann]

Pleasure

[wiegelmann]

@devurandom Any ideas how to solve?

[devurandom]

What you need is a way to sort out which key is "the right one" for a certain email address.

The easiest to implement is probably to provide the user with a choice, if there are multiple valid pubkeys for the recipient he entered.

The idea that came to my mind earlier (s.a.) is to use the web-of-trust for that, which of course requires maintenance. For example, the sender inputs his email address, encrypt.to allows him to choose the pubkey for that (from a list of valid keys with that uid), when he enters the recipient, the recipient keys that are connected to the sender key via the web-of-trust are presented to the user (preferred above all others). The maintenance of a web-of-trust to make that possible, without people having to install GnuPG or similar, is a bit complex (you need to allow finding other people's keys and signing them) - thus the idea to couple it with a social network where this is somehow integrated.

[wiegelmann]

@devurandom Now the user can select the public key in the advanced mode.