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The question really says it all. Is it possible to have a secure connection from a WiFi-server to a WiFi-client through any common protocol, that doesn't require the server and the client to share a secret?

If so, how can that work?? :-)

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How can you set up encryption without a shared secret? SSL kinda works that way, do you mean never share a secret, or don't share a secret initially? –  NickW Jun 7 '13 at 13:38
    
Never share a secret. Imagine setting up a WiFi-Network which is not password protected. Is there a way to make that network tap-proof anyway? –  Lea Hammerschmidt Jun 7 '13 at 13:39
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I believe that once you're on the wifi network, you can see all the traffic that's in radio range of you. I think you need connection-level security (SSL, SSH, TLS) or encapsulation (a VPN). –  pjc50 Jun 7 '13 at 14:01

1 Answer 1

It's not as daft a question as it may first appear:

  • An access point is configured to back off authentication to a RADIUS server.
  • The RADIUS server has its own certificate authority which issues certificates to clients. Certificates, once issued, can be revoked.
  • When a client connects, it presents its certificate via the access point to the RADIUS server, which decides whether authentication should succeed. The certificate must be signed by the server, and must not appear on its certificate revocation list.
  • If the client is successfully authenticated, the RADIUS server sends an encryption key back to the access point, which is used to encrypt the connection.

This configuration (alphanumeric soup: EAP-TLS via WPA2/802.1x) means that the client doesn't share a simple secret with the server.

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No, the certificate doesn't need a passwords, just as certificates from websites don't have passwords: the purpose of them is to say 'look at me, I have the key, let me in!'. This technique can be combined with a username/password pair but it's not necessary. –  Flup Jun 7 '13 at 14:21
    
As I said: the certificate doesn't need a password. It can have one, but doesn't need one. –  Flup Jun 7 '13 at 14:33

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