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Scramble.io: secure email for everyone

dcposch.github.io

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Re: Scramble.io: secure email for everyone

#81

Post by jaekwon »

jahewson wrote: post #37
jaekwon wrote: post #16

Earlier quoted context omitted.

You can have a signing committee vet the asset files and publish the signatures, which the browser extension looks for. It allows an upgrade path without having to go through the browser app store. For example, browser extensions installed using the Chrome app store updates automatically, which implies trust in Google. The browser extension would only load vetted assets onto the DOM. In other words, you visit the sit…

Or just have the signing committee publish signed JS code. There's no real difference between that and publishing a signed hash. Unfortunately other hostile extensions are still free to mess with the DOM, so it's all a bit pointless.

A secure environment would require a vetted browser and no other hostile extensions. That's certainly possible, so Scramble does have a use.

Re: Scramble.io: secure email for everyone

#82

Post by dcposch »

davedx wrote: post #2

Fantastic. Tighten up the user interface and this should gain traction. Checking out the Github repo now.

Thanks! We're working on improving the UI. A few upcoming fixes:

* Clear visual distinction between encrypted and unencrypted mail * Keep track of read vs unread mail * Allow users to enter a public key for an external (non-Scramble address) and sent encrypted mail to existing PGP users * Basic search

Re: Scramble.io: secure email for everyone

#83

Post by tptacek »

jaekwon wrote: post #79
tptacek wrote: post #64

Earlier quoted context omitted.

You say that because you want it to be true, not because you have any real confidence that it is true.

What you said applies more to you than it does to me.

Usually, when people claim to have refuted our crappy old article on Javascript crypto, they have some misguided but at least potentially falsifiable argument for having accomplished that; for instance, "there are browsers with secure RNGs now".

You don't even have that. From what I can tell, you have literally no argument at all; instead, you "agree" with the article while drawing exactly the opposite conclusion that the article draws, then point out again and again how much users don't want to install things, as if that changed the security of this system at all.

Re: Scramble.io: secure email for everyone

#84

Post by hershel »

dcposch wrote: post #40
tptacek wrote: post #7

Another week, another Javascript cryptography project. See: https://news.ycombinator.com/item?id=6637915 https://news.ycombinator.com/item?id=6420739 https://news.ycombinator.com/item?id=6353137 https://news.ycombinator.com/item?id=6317685 (That's just the last few weeks). We are also developing a browser extension which will verify the Javascript loaded from the server. (Until then, an attacker who gained control of…

Yeah, I read your Matasano post, "Javascript crypto considered harmful", and I agree-- Javascript crypto is hard! But it's not impossible. The reason I chose that route is because I want to make it as easy as possible for users to try out and adopt. Just testing it out? No installation required. I think that security is at least equal parts a technical problem and an adoption problem. The status quo is that nearly al…

>> I want to make it as easy as possible for users to try out and adopt. Just testing it out? No installation required.

Why not offer an option to try it out in the browser(with same GUI), and if they want security tell them to install it(and verify)? It would be just a bit harder than installing the extension.

BTW:there's another use case for extension based encryption: As the backbone for private messaging for various sites(which requires integration with the browser) , for example reddit.

private messages in reddit are :

(a)viewable to sniffers due to http usage

(b)can be viewed by reddit staff

(c)can be viewed by dragnet and targeted surveillance

An extension would definetly reduce attack scenarios, and has a good viral marketing vector. In fact implement the right way i could see it being a very reliable way to making something like this popular.

Re: Scramble.io: secure email for everyone

#85

Post by dcposch »

brown9-2 wrote: post #78

Users don't have to manage and back up their keys---or even know what a key is. Scramble does it for you. As a user, why would I want to delegate my key management to you? Encrypting the email I want to send to a person with their public key is what gives me a sense of trust that what I am sending is encrypted and only readable to that person. However--as the example of Tormail and others show us--the server cannot b…

> As a user, why would I want to delegate my key management to you?

The beauty of it is that Scramble encrypts and signs whenever the recipient is also a Scramble address--automatically. The goal is to protect even users who don't know what a "PGP key" is.

(Don't get me wrong, we're planning improvements for power users as well--for example, we want to make it easy to use Scramble over Tor. But the goal really is "Encrypted email for everyone".)

> So then why am I trusting you with my PGP keys?

No, as explained in the writeup, the server stores your private key encrypted with your passphrase. The server never sees your passphrase, or your private key.

We've used a good key derivation function (scrypt)---this makes it difficult to brute-force the password.

In short: Yes, the server stores things so that you get the Gmail experience, sit down at any computer and it just works. No, the server never sees your plaintext private key.

Thanks for the feedback! If I get a chance, I'll paraphrase your questions and add them to the upcoming FAQ.

Re: Scramble.io: secure email for everyone

#86

Post by tptacek »

jaekwon wrote: post #77
peterwwillis wrote: post #69

Earlier quoted context omitted.

How are you going to block dragnet surveillance if they can surveil the method of your delivering encrypted messages? NSA can already see, and modify, the JS used to create encrypted messages (because they've owned the HTTPS gateways), so they can see, and modify, the encrypted messages.

If they do this for many users, then those who don't have a secure environment (including the browser extension) are vulnerable, but it would be easy to detect that this is happening on a large scale -- those running the extension would be notified. If they don't do this for every user, then it wouldn't be effective dragnet surveillance, and Scramble would have a made a dent in dragnet ability.

Let's stipulate that your detection system, which does not currently exist even as a design document, actually works. By your own admission, only a small minority of users will actually install it. Now: a whistleblower in the USG, who is much more likely not to be a "power user" (if they were clueful they wouldn't be using this system to begin with) leaks a document from your service to a journalist and begins a conversation.

The FBI decides they'd like to read that conversation. They issue a court order requiring you to hand over your TLS private key, and use it to MITM your users to feed them corrupted JS code that discloses PGP private keys.

The small minority of users "detect" this change. But not quickly enough: the whistleblower has already logged in to check their mail, and has now disclosed their private key to the FBI.

What now? What's the feature you're going to build to keep that from happening?

Not only are you using Javascript crypto to provide this "service" to users, but you're not even forward secure.

Re: Scramble.io: secure email for everyone

#87

Post by peterwwillis »

jaekwon wrote: post #77
peterwwillis wrote: post #69

Earlier quoted context omitted.

How are you going to block dragnet surveillance if they can surveil the method of your delivering encrypted messages? NSA can already see, and modify, the JS used to create encrypted messages (because they've owned the HTTPS gateways), so they can see, and modify, the encrypted messages.

If they do this for many users, then those who don't have a secure environment (including the browser extension) are vulnerable, but it would be easy to detect that this is happening on a large scale -- those running the extension would be notified. If they don't do this for every user, then it wouldn't be effective dragnet surveillance, and Scramble would have a made a dent in dragnet ability.

Could you be more specific? I don't know who "everyone" is, or what a large scale is, or who is detecting what by whom. In any case, I don't see how anyone could detect real HTTPS MITM.

If the Scramble.io people ship ALL OF THE PROGRAM LOGIC IN THE EXTENSION, it could be secure. But if any program logic (javascript) they interpret is delivered to the user via HTTPS, it will not be secure.

In general, dragnet security will always be possible as long as you can do statistical analysis over both targets in the network (or the whole network), which the NSA has proven it can do.

Re: Scramble.io: secure email for everyone

#88

Post by tptacek »

jmccree wrote: post #72
mdip wrote: post #33

It's nice to see so many projects attempting to solve this problem. I have a question specific to the documentation on the main page: Private keys are stored on the server in encrypted form. The key derivation function used is as follows: K = scrypt(Passphrase, Username) I'm going to skip the "JS crypto is bad". What I'd like is clarification of the Zero Knowledge section that the keypair is decrypted client-side onl…

Even with the brute protection provided by scrypt, it's very worrying that you can assume the encrypted private key will A) Be available to authorities via (secret) court order B) Captured and stored by NSA types. The security of the key could only be assumed to be as high as the weakest passphrase ever used by the user. With what we know about most user's password security (especially the type not already capable of…

Because only a subset of possible users has clientside storage available for keys, and this project doesn't care about security, it cares about maximizing the number of users it can obtain.

Re: Scramble.io: secure email for everyone

#89

Post by eli »

hershel wrote: post #84
dcposch wrote: post #40

Earlier quoted context omitted.

Yeah, I read your Matasano post, "Javascript crypto considered harmful", and I agree-- Javascript crypto is hard! But it's not impossible. The reason I chose that route is because I want to make it as easy as possible for users to try out and adopt. Just testing it out? No installation required. I think that security is at least equal parts a technical problem and an adoption problem. The status quo is that nearly al…

>> I want to make it as easy as possible for users to try out and adopt. Just testing it out? No installation required. Why not offer an option to try it out in the browser(with same GUI), and if they want security tell them to install it(and verify)? It would be just a bit harder than installing the extension. BTW:there's another use case for extension based encryption: As the backbone for private messaging for vari…

I think you can do that now with one of the GPG browser plugins (or just copy/pasting from a GPG app)

Re: Scramble.io: secure email for everyone

#90

Post by jaekwon »

peterwwillis wrote: post #76

so, you want to send someone a message. you don't care if someone sees you sending it. but you don't want anyone to know whom you sent it to, or what the message contains. requirement 1. message integrity and security 1a. use public-key cryptography - step 1. Person A writes a letter to Person B. - step 2. Person A encrypts a message using Person B's public key. - step 3. Person A sends encrypted message to Person B.…

Yes, we're on the same page! We have an idea for how fake messages would be passed around fake friends, and how to grow this "dark" network organically. Let's collaborate!
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