3 ms·

I'm building a chat platform with js and https crypto. It's better than nothing in my opinion.

by cmdrfred 10y ago

JustSomeNobody 10y ago
A false sense of security is worse than nothing at all.
- cmdrfred 10y ago
  Is it worse than just Https? I'm not advertising the feature loudly, I just want to keep nosy sysadmins on corporate networks with https inspection out of private conversations. It obviously can be broken by NSA types if they want to actively alter traffic, but passive monitoring should be harder. Also this forces the attackers hand, an attack against this system can be detected if you want to spend the time comparing hashes.
  - forgotpwtomain 10y ago
    > Also this forces the attackers hand, an attack against this system can be detected if you want to spend the time comparing hashes. You could have an extension which checks the hash of the js/html payload against a publicly known and signed hash prior to running and rejects it otherwise. It's still browser crypto but potentially you do better than 'everything is broken if the ssl session is hijacked'.
- bigiain 10y ago
  True - and it's complex - but you need to keep the capability of your adversary in mind. This will thwart your nosy flatmate/little-brother. This is reasonably likely to keep curious or nosy corporate IT or HR staff at bay if you use it at work. It's not going to keep a properly authorised and resourced corporate IT investigation/surveillance out - at least not for any hardware that's got corporate ssl roots installed (or device management that allows installation of those). It'll likely keep local cops out. It's less likely to keep feds out if they're determined. It 100% will not help against people who've got browser trusted ssl signing roots and the ability to run QUANTUM on exploited backbone routers to deliver their own versions of the javascript appropriately ssl encrypted to you before the actual site has a chance to respond.
  - cmdrfred 10y ago
    Another vector is I won't really be able to respond to requests from law enforcement because as soon as the chat is over (or on request of the creator of the chat) I wipe the key from memory. Leaving only encrypted blobs in the database that are then purged themselves at a later time. The key is never written to the disk to prevent forensic analysis there as well. As a bonus, I can handle a decent number of users with a small amount of hardware as most of the hard work is done client side. Lastly, I'm planning on implementing all of the best protections we have against man in the middle attacks currently like subresource integrity and HSTS. If the browser committees give me something better (maybe some sort of resource signing that can be verified on a secondary secure channel?) I'll implement it. So it may protect against more in the future.
    - bigiain 10y ago
      That kind of policy didn't work out so well for Ladar Levison at Lavabit when they wanted to subvert the entire userbase's security just to get access to Snowden's email account... If you piss off important enough people - law enforcement won't just go away when you say "the system isn't capable of doing that", they'll say "so re-write the system so it is, and if you tell anybody we'll put you in jail forever". The FBI have seized and continued to run a child porn website before to gather evidence - do you _really_ think they'd hesitate before taking over your encrypted chat servers if they thought it'd get them a career-advancing prosecution? Do you think you'd fight as hard as Ladar did when the guys with guns come knocking at your door? (I have no doubt I'd cave pretty quickly - I've got a lot of respect for Ladar's resistance to selling out his users...)
      - cmdrfred 10y ago
        I thought of that, the project will be FOSS and I'm going to encourage people to run their own servers. The primary server will mostly be a reference implementation and for casual chatting.

I'm building a chat platform with js and https crypto. It's better than nothing in my opinion.

JustSomeNobody 10y ago

A false sense of security is worse than nothing at all.

cmdrfred 10y ago
Is it worse than just Https? I'm not advertising the feature loudly, I just want to keep nosy sysadmins on corporate networks with https inspection out of private conversations. It obviously can be broken by NSA types if they want to actively alter traffic, but passive monitoring should be harder. Also this forces the attackers hand, an attack against this system can be detected if you want to spend the time comparing hashes.
- forgotpwtomain 10y ago
  > Also this forces the attackers hand, an attack against this system can be detected if you want to spend the time comparing hashes. You could have an extension which checks the hash of the js/html payload against a publicly known and signed hash prior to running and rejects it otherwise. It's still browser crypto but potentially you do better than 'everything is broken if the ssl session is hijacked'.
bigiain 10y ago
True - and it's complex - but you need to keep the capability of your adversary in mind. This will thwart your nosy flatmate/little-brother. This is reasonably likely to keep curious or nosy corporate IT or HR staff at bay if you use it at work. It's not going to keep a properly authorised and resourced corporate IT investigation/surveillance out - at least not for any hardware that's got corporate ssl roots installed (or device management that allows installation of those). It'll likely keep local cops out. It's less likely to keep feds out if they're determined. It 100% will not help against people who've got browser trusted ssl signing roots and the ability to run QUANTUM on exploited backbone routers to deliver their own versions of the javascript appropriately ssl encrypted to you before the actual site has a chance to respond.
- cmdrfred 10y ago
  Another vector is I won't really be able to respond to requests from law enforcement because as soon as the chat is over (or on request of the creator of the chat) I wipe the key from memory. Leaving only encrypted blobs in the database that are then purged themselves at a later time. The key is never written to the disk to prevent forensic analysis there as well. As a bonus, I can handle a decent number of users with a small amount of hardware as most of the hard work is done client side. Lastly, I'm planning on implementing all of the best protections we have against man in the middle attacks currently like subresource integrity and HSTS. If the browser committees give me something better (maybe some sort of resource signing that can be verified on a secondary secure channel?) I'll implement it. So it may protect against more in the future.
  - bigiain 10y ago
    That kind of policy didn't work out so well for Ladar Levison at Lavabit when they wanted to subvert the entire userbase's security just to get access to Snowden's email account... If you piss off important enough people - law enforcement won't just go away when you say "the system isn't capable of doing that", they'll say "so re-write the system so it is, and if you tell anybody we'll put you in jail forever". The FBI have seized and continued to run a child porn website before to gather evidence - do you _really_ think they'd hesitate before taking over your encrypted chat servers if they thought it'd get them a career-advancing prosecution? Do you think you'd fight as hard as Ladar did when the guys with guns come knocking at your door? (I have no doubt I'd cave pretty quickly - I've got a lot of respect for Ladar's resistance to selling out his users...)
    - cmdrfred 10y ago
      I thought of that, the project will be FOSS and I'm going to encourage people to run their own servers. The primary server will mostly be a reference implementation and for casual chatting.