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Telegram - secure, free messaging

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Re: Telegram - secure, free messaging

#131

Post by tptacek »

jgg wrote: post #115
sillysaurus2 wrote: post #33

Earlier quoted context omitted.

He's done nothing in crypto, and he's rolled his own protocol. That's historically been recipe for disaster regardless of how many honors you hold. Colin Percival is similarly decorated, along with being a cryptographer (he's the FreeBSD security officer): http://www.daemonology.net/papers/ ... yet even his crypto app Tarsnap was broken for over a year before he noticed, due to a typo during an innocent-looking refac…

I scratched my head after reading your comment, and waited to see if anyone else would say something. Colin's problem was that his (hand-written, from the looks of it) crypto primitives allowed him to use AES-CTR with a non-incrementing counter. I'm not sure if it's appropriate to say that in relation to a comment about "rolling your own protocol." I see that as a low-level problem. Further, you've pulled a misdirect…

The extension you're thinking about is Trevor Perrin's Axolotl ratchet, which is (a) the product of an actual cryptographer, (b) used in more than one system (it's also incorporated into Adam Langley's Pond), (c) has been reviewed by experts, and (d) is entirely specified, with a public domain spec.

It is not in fact reasonable to compare Telegram's ad-hoc protocol to the "extensions" TextSecure has.

Re: Telegram - secure, free messaging

#132

Post by tptacek »

bnr wrote: post #108
na85 wrote: post #7

From their FAQ: > Q: How secure is Telegram? > Very secure. We are based on a new protocol, MTProto, built by our own specialists from scratch, with security in mind. At this moment, the biggest security threat to your Telegram messages is your mother reading over your shoulder. We took care of the rest. Oh good, a bunch of randoms have rolled their own crypto. I stopped reading at this point.

They did not roll their own crypto, it's using AES with Diffie-Hellman key generation. [0] You can now argue whether that's still "from scratch". (Is building something on top of TCP "from scratch"?) [0] http://core.telegram.org/api/end-to-end

Designing new protocols and constructions using primitives like AES and DH is exactly what cryptographers are talking about when they refer to "rolling ones own crypto".

Look at the description of their protocol, particularly the handshake, which negotiates number-theoretic parameters, and try to make a list of all the checks they'll need and the additional protocol that they'd need to specify just to make the handshake secure.

Not only that, but the crypto in Telegram is idiosyncratic; for instance, this is the only system I've ever seen that used IGE mode.

Re: Telegram - secure, free messaging

#133

Post by tptacek »

gr3yh47 wrote: post #102
na85 wrote: post #7

From their FAQ: > Q: How secure is Telegram? > Very secure. We are based on a new protocol, MTProto, built by our own specialists from scratch, with security in mind. At this moment, the biggest security threat to your Telegram messages is your mother reading over your shoulder. We took care of the rest. Oh good, a bunch of randoms have rolled their own crypto. I stopped reading at this point.

With all the revelations of built in weaknesses and such with existing encryption schemes... I don't know. I think we need a new one. That said, it should probably be developed by a panel of experts. I would love to see something by Bruce Steiner et al, where 'et al' is a group that he selects. As you pointed out a group without heavy crypto experience can't realistically roll their own and have it actually be secure…

Which revelations would those be?

Re: Telegram - secure, free messaging

#134

Post by ge0rg »

utnick wrote: post #127
ge0rg wrote: post #114

Earlier quoted context omitted.

Sorry, but this is just a lame excuse. There is no need to upload the personal names for this feature. Also, there are approaches to make number registration lookups more secure, e.g. bloom filters: http://en.wikipedia.org/wiki/Bloom_filter I would expect such an approach from a "secure" app.

Don't Bloom filters provide just an illusion of privacy when talking about phone numbers because its easy to iterate through every possible number?

I am not quite sure how the dimensioning of the bloom filter affects the false positive probability. Of course it is easy to iterate through many phone numbers, but at least you can not know for sure if a probed number is actually in the filter or just a false positive, giving means of plausible deniability.

I did not want to imply that there is a perfect zero-knowledge synchronization mechanism for your contact book.

Re: Telegram - secure, free messaging

#135

Post by ge0rg »

TelegramApp wrote: post #129
ge0rg wrote: post #107

I have not run the app, but from the Android source code it looks like this "secure" app is uploading your contacts including full names and all their phone numbers into the "cloud": MessagesController.readContacts() [0] is called on creation of the MessagesActivity. When invoked for the first time, it collects first names, last names and phone numbers from the Android Contacts interface, creates a table containing t…

That is correct, Telegram does upload names and numbers — naturally, after receiving permission to do so. (see also: http://telegram.org/privacy ) Apart from identifying Telegram users among the user's friends, this also enables us to use proper names in notifications on the iPhone, as well as facilitates moving between devices. But you have highlighted an important issue. Our android developer relied on the system p…

naturally, after receiving permission to do so.

This is not quite true. I never gave anyone (especially not the users of WhatsApp or Telegram) permission to upload my personal information to any cloud services. You can not actually imply that permission from all contacts merely by asking the user.

this also enables us to use proper names in notifications on the iPhone

I do not know enough about the iOS internals, but my naive assumption would be that after receiving a push notification, you can run code locally (like get the contact name from a local database), not merely get the notification displayed by the OS.

We will add another prompt in the coming version.

This is an improvement, but unfortunately does not tackle the first issue I mentioned, with implying consent from the actual contacts.

Re: Telegram - secure, free messaging

#137

Post by salient »

techquery wrote: post #49
conroy wrote: post #3

The important thing to remember is that all Telegram messages are always securely encrypted. The difference between messages in Secret Chats and ordinary Telegram messages is in the encryption type: client-client in case of Secret Chats, client-server/server-client for ordinary chats. Where "securely encrypted" means that the Telegram server has full access to message contents for ordinary chats. All chats should be…

I guess, that the problem is in encryption key exchange. Cloud chats are easy to synchronize between devices. Secret chats require unique encryption key for each chat.

Look into this:

https://whispersystems.org/blog/advanced-ratcheting/

Re: Telegram - secure, free messaging

#138

Post by TelegramApp »

na85 wrote: post #7

From their FAQ: > Q: How secure is Telegram? > Very secure. We are based on a new protocol, MTProto, built by our own specialists from scratch, with security in mind. At this moment, the biggest security threat to your Telegram messages is your mother reading over your shoulder. We took care of the rest. Oh good, a bunch of randoms have rolled their own crypto. I stopped reading at this point.

We have not 'rolled our own crypto'. We still use RSA, AES and DH.

I've changed the part in the FAQ that seems to be one of major sources of this controversy, so that it no longer reads "built from scratch". This was poorly applied marketing language — we do use time-tested security algorithms. Even though Telegram doesn't uses MTProto instead of HTTPS due to mobile speed and trust issues.

Re: Telegram - secure, free messaging

#139

Post by salient »

utnick wrote: post #120

A lot of haters in this thread. To be expected. I've been following this space for a while and telegram is the best app out there right now. The usability is great and they are trying to do the right things when it comes to security. The apps are open source and can be audited. I fully expect there to be bugs, that is part of the process! You would be insane to trust your life to a crypto app thats been around a few…

They are making a lot of bogus claims using marketing speak, and they are very low on details, while saying the app will be opensourced "eventually".

For a "security" app, hell yeah you should be skeptical. Right now I think the most interesting and most trustworthy secure messaging projects are TextSecure v2 and Dark Mail (granted, that one isn't even out yet, their ideas so far sounded quite good).

Re: Telegram - secure, free messaging

#140

Post by anu_gupta »

utnick wrote: post #120

A lot of haters in this thread. To be expected. I've been following this space for a while and telegram is the best app out there right now. The usability is great and they are trying to do the right things when it comes to security. The apps are open source and can be audited. I fully expect there to be bugs, that is part of the process! You would be insane to trust your life to a crypto app thats been around a few…

> In a few years this could turn into a really nice , secure app.

And that would be a better time to market it as "very secure"

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