[erlang-questions] Using my own Diffie-Hellman + AES instead of SSL

[Dmitry Kolesnikov]

Hi,

If "trusted gateway" assign the session key both to client & server then this would be a good compromise. 

You original concern was a memory overhead for SSL. So you still have SSL in picture and it is handled by GW instead of Servers. 2min TTL is not long enough to dramatically reduce a load. I am not sure if you set-up becomes optimal in terms of costs. Have you estimated GW capacity vs Servers?

- Dmitry

On Jun 8, 2012, at 2:06 PM, Morgan Segalis wrote:

> Hi !
> 
> As I explained answering Angela, Here's my idea for the connection protocol I'm thinking about.
> 
> 1) The client should connect WITH SSL to a gateway (With Certificate and strong Cipher)
> 2) Client and Server will negotiate a key together along with a sessionID (not sure we need Diffie-Hellman since it is a secure connection)
> 3) The sessionID + key will be stored in a cassandra database (With a TimeToLive of 2min or less)
> 4) The server will tell to which node the client should connect
> 5) Client disconnects from gateway
> 6) Client connects to the node specified by the gateway, and gives the SessionID to the node (in clear)
> 7) The Server node retrieve the Key from the cassandra db
> 8) If it exist, it sends an accept to the client encrypted, if not, it disconnects the client and we are back to square 1.
> 9) Both client & server can communicate over AES using the key they now both have.
> 
> in part 4, the gateway, a trusted SSL server will give the ip of the node the client should connect (encoded of course). This will make the client able to trust the server.
> in part 8, the node will accept the client by sending him a specific message, that only a trusted server could have sent. This will make the client able to trust the server.
> 
> I'm confident this protocol is secure, and will allow me to have solid encryption while having a good ratio memory/client.
> But I might be wrong… 
> 
> Thanks !
> 
> Le 7 juin 2012 à 14:29, dmitry kolesnikov a écrit :
> 
>> Hello,
>> 
>> I guess you can use crypto:dh_compute_key for DH key exchange procedure.
>> 
>> Your application cannot trust server w/o certificates. Therefore
>> number of attacks are possible. If you are fine with all related
>> threats then yes this is good option to save memory.
>> 
>> On another hand, if you need to use multiple transport e.g. Tcp + udp
>> then it is good as well.
>> 
>> Btw, C ssl API allows to perform SSL:read/write directly to memory. It
>> would be cool if such feature is available in Erlang. I suppose it
>> might help to reduce memory footprint for some applications
>> 
>> Best Regards,
>> Dmitry >-|-|-*>
>> 
>> 
>> On 7.6.2012, at 13.35, Morgan Segalis <msegalis@REDACTED> wrote:
>> 
>>> Hi everyone,
>>> 
>>> As always (for those who remember my old posts), I'm looking to reduce the memory footprint of a secure connection to my server.
>>> 
>>> I'm right now looking into doing my own Diffie-Hellman key exchange + AES 128-bit encryption over a TCP connection instead of using Erlang SSL.
>>> Using SSL with this kinda feels like using a bazooka for smashing a fly.
>>> 
>>> The thing is, I do not really need certificates, since the connection url is embedded in a application, and it is using a proprietary protocol.
>>> 
>>> Before trying to implement this solution, I would like to hear pros and cons, from Erlang experts on this mailing lists ! (others are welcome too of course ;-) )
>>> 
>>> I'm actually looking to implement the same thing as here http://blog.diginux.net/2006/11/15/adding-aes-encryption-to-erlang-chat/
>>> 
>>> Thanks for your help.
>>> 
>>> 
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>