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Comment by rdl | Hacker News Reader

Seems like it would be better to go with S/MIME or OpenPGP for this. S/MIME would potentially be able to re-use some of the browser's own code for handling certs.

Symmetric crypto (like this) is relatively easy to implement, but a usability nightmare.

A browser extension is still a lot better than a general webapp for security.

I wish someone issued "mail-from" auth personal certs for ~free to end users, integrated into apps for cert request/signing/etc. StartCom's StartSSL sort of does (for "level 1" personal certs), but their cert issuance UI is a huge pain. It really needs to work with the "I have no cert, I'm going to use an app for a specific purpose, I get a cert incidental to signing up for the service, I then can use the cert for other purposes", which none of the x509 crowd really support.

WoT on the certs would be cool too (which startcom is trying, but since it's a pain to use, there aren't enough people, so it doesn't work.)

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Actually we went down the gpg public/private key path first, and realized that was way worse in terms of usability. Even though with symmetric you have to enter the password, at least average users know what that means.

Try to get an an average user to do a key exchange, backup their private key or even know what a key is as some other solutions require.....

We're trying an approach with http://parley.co that involves storing a symmetrically encrypted OpenPGP keyring on the server for our users. That, combined with a UI that automatically takes care of key sharing and discovery, results in a system that's easy for the average user, integrates with the existing PGP ecosystem, and is at least as secure as a symmetric scheme (like symmetric systems, the strength is limited by the passphrase, but at least users can each have their own).

I'm all for anything that makes moving one's private key between devices easier, and I understand that you've made a conscious compromise between security and usability, but wouldn't it be possible to achieve both goals, for example by enabling private key syncronisation between devices without the key having to be uploaded to a third-party server?

This would also eliminate the need for the additional passphrase, as the point-to-point key trasfer could by programatically encrypted / decrypted without user intervention.

That's a great idea, and I see no reason that it couldn't be done. Removing the centralized target would obviously be beneficial, but I'm not sure it would be possible to increase security for individual users that much: If the only common information between the two devices is what's in the user's head (email, password) then you'd still need a server to negotiate the exchange (by telling the new device where to find the first one) which would leave the whole system vulnerable to many of the same targeted attacks as the centralized design (MITM or malicious actor at the server trying to brute force individual keys).

I agree, but it should still be possible mitigate those sorts of threats without the user needing anything else in thier head (at least more than temporarily :-), even if the password for the negotiation was successfully brute-forced / MITM'd so that a foreign device could initiate a private key transfer, and even if the private key exchange itself was MITM'd.

Perhaps for example using a one-time shared secret either displayed on one device and entered in the other, or entered by the user on both devices as a temporary pass-phrase. This could then form part of a D-H style key exchange, or even be the encryption passphrase as in your proposed model, but only used temporarily while the private key is transferred, so not having to be remembered by the user for a centrally stored copy of the private key.

I appreciate you're probably well down the track on your current model, but it would be really nice to see something like this developed, and ultimately standardised, as like you mention in your manifesto, private key management (and especially transfer and backup) is one of the larger usability barriers to wider adoption of public-key cryptography.

now THAT is the way to do it! Yes, the average user has trouble grasping the CRITICAL IMPORTANCE that the user, AND ONLY THE USER, must physically hold the private key. There's no problem with having the public keyring in the cloud, and I don't even see any reason to keep it encrypted. It's called the PUBLIC key for a reason, to paraphrase Whit Diffie. You guys are on the right track...tools that make REAL 4096-bit PKE EASY are what are needed (Certainly it is an understatement to say that a 4096-bit elliptical curve DH cryptogram is "at least as secure as symmetric keys" - indeed, symmetric schemes are several orders of magnitude weaker, even with the same size passphrase) . But users will have the "inconvenience" of having to store their PRIVATE KEY on all their devices; but hey, that's not much work to be virtually impregnable. I applaud Parley's efforts!

Thank you for the kind words, but just to be crystal clear: we are storing the users' private keys on the cloud, hence the symmetric encryption. It's certainly a trade-off, and not the right option for everyone, but it lowers the barrier to entry for OpenPGP enormously.

Really admire what you're doing here, but proposed pricing seems off (just my opinion). If you think we'd be better off moving to a "encrypted by default" world, then limiting paying users to sending 150 messages a month isn't a good way to do it! Especially when I know it doesn't cost that much to do so.

I appreciate the feedback! Pricing is tricky, and we're open to suggestions--our challenge is basically to earn most of our profit from business users while keeping it inexpensive for consumers. Maybe the number of messages is the wrong way to separate the two camps, though. Any ideas?

(Is 150 messages/month really limiting for average users? I don't think I've sent anywhere near that much personal mail this month, but I may be an anomaly.)

EDIT: I forgot to mention that whichever way we end up doing it, the personal plan will be free for anyone who signs up for the mailing list before August 1.

I would try to differentiate based on features, vs. messages. Businesses care about:

* third-party administrators being able to create/update/etc. accounts (either consultants for small companies, or IT staff for larger companies) -- this is the #1 way to differentiate a consumer service from a business service.

* document retention policy (which is really document destruction capability

* escrow (corp escrow keys)

* escrow for in-line checking of messages (either DLP, or AV, or archiving for compliance with SEC or other regulators)

* certifications of compliance

* support

* maybe custom domain names and other trickery (including stuff like splitting domain names to both work with existing exchange servers or google apps plus your service

* service level agreements, indemnity, etc.

* integration into stuff like Active Directory (LDAP) for account provisioning and credentials

* Maybe 2FA (although I'd argue 2FA should be a base feature, but for mail it isn't very meaningful except if you do cert auth or cookie/ip blessing of systems + stored imap or web browser password to log in + your passphrase stuff for the crypto, and then a non-cert 2FA thing is only meaningful to management

I don't think you need to worry about marginal 5-10 user businesses using the free service instead of a paid service; I'd focus on making sure you can make real money on 100-500+ user businesses, or small businesses which will grow into those, and then on getting as many free users as possible to try to drive conversions. I'd rather sell 10 companies with 500 users each than 50 companies with 5 users each.

Awesome feedback as usual. Thanks Ryan! That gives us a lot to think about.

My first thought is number of recipients. If you allowed low-tier users to send messages to e.g. 5 people at a time, and any more required the business plan, that seems like a good way to separate the two.

Number of recipients seems like a good idea for separating personal and business to me too. Personally, I only use PGP for emails with my partner, but we definitely send way in excess of 150 messages a month.

I'm all for a world where people start using encryption as a matter of course, so I really the OP's product works out. It'll finally get rid of that "you must have something to hide" mentality, when all you really want to do is protect yourself from the odd security vulnerability or a grumpy sys admin with an axe to grind!

That's a great idea, thanks for the suggestion! I'll be making some changes to reflect that.

The open source webmail application "Roundcube" combined with the "openpgp_rc" plugin which utilises the "openpgp.js" library, works as follows:

You can generate your keys in the browser, or paste in an existing key. The key is then stored in HTML localStorage in the browser. If you ever clear your localStorage, you have to paste it in again. But this way, the key never goes near the server.

Your method is suitable for most people who can't be bothered backing up their keys. Choice would be a good thing though.

That's a cool way of doing it! Of course, the usual caveats about in-browser crypto still apply, but still neat.

I agree that choice is great, and we might expose manual key management in Parley at some point, but realistically people who know how to do that (and have the desire to) already have many options.

minor nitpick - it sounds like parley is storing the encrypted private keys on their server, encrypted with the user's passphrase.

This method is the best tradeoff with cloud encryption IMO - convenience of having the key file accessible anywhere, even if it is not as secure as copying it yourself to all your devices. Also, much much better than using symmetric keys.

Our thoughts exactly :)

>> storing a symmetrically encrypted OpenPGP keyring on the server

> now THAT is the way to do it!

Um, no. No, it absolutely is not.