Diffie hellman openvpn why

Information Security Stack Exchange is a question and answer site for information security professionals. It only takes a minute to sign up. Connect and share knowledge within a single location that is structured and easy to search. However, I cant see why the certificates are used in conjunction with DH. I think about this in the following way: The certificates and private keys are used for asymmetric encryption so all the encryption is done asymmetrically which is not practical , while DH is used to generate the secret key in order to use HMACs to ensure message authentication.

So we have two cases for a secure exchange to occur. Alice signs a message to Bob, and encrypts the message with Bob's public key. Sends message to Bob.

Bob decrypts with his private key. Verifies the signature to ensure that Alice sent it. The message is going to be a symmetric encryption key. This is what's used to secure the connection. The Diffie Hellman exchange relies on two separate entities generating a secret value. Through some math magic they're both able to generate a common secret value. This common secret is what is used as a symmetric key or to derive symmetric keys.

All rights reserved. All other tradenames are the property of their respective owners. Submit Search. Account Settings Logout. Both peers can now encrypt, transmit and decrypt data using their symmetric keys. However some concerns were found later within the Diffie-Hellman algorithm such as Man-in-the-middle attacks as there is no authentication in place before keys are exchanged.

How would peer B know that it is about to exchange keys with peer A? This led to the more advanced public key cryptography in RSA. However using authentication methods such as pre-shared keys and digital certificates to authenticate VPN gateway devices has overcome this issue. All of these files can also be embedded into the configuration file. If that is done, the configuration file must be protected as you would do with the private keys. All this is why we in the upstream OpenVPN community have started to point users at this wiki page , the guidance you get on the Interwebs can be quite full of flaws.

We don't believe in a "standard" setup, as there are too many variables which makes up a VPN. It is more important to understand which options you need to get a safe start and why you need to use them. Configuring a VPN isn't easy if you want to do it correctly and securely. Skip to content. Sign in Sign up. Instantly share code, notes, and snippets. Created Sep 12, Code Revisions 1 Stars 9. Embed What would you like to do? Embed Embed this gist in your website.

Share Copy sharable link for this gist. Learn more about clone URLs. Download ZIP. Small OpenVPN setup tutorial. Set to or bigger in Change into the easy-rsa directory and source the vars file, since those are used by most scripts: cd easy-rsa source vars Start with a clean slate:.

Create the self-signed certificate authority Use a password to protect the CA :. Please enter the following 'extra' attributes to be sent with your certificate request A challenge password []: Generate Diffie-Hellman parameters.