Is something that connects two different networks through a public network (public network) so that users seem to be in the same network (virtual). Because data sent or received from two connected networks must be sent over the public network, VPNs have mechanisms to secure data. Now, thanks to these security features, VPNs are often used to prevent eavesdropping and censorship from third parties (man in the middle attacks).

Openvpn connections will usually use HTTPS to forward the data sent, but keep in mind that HTTPS works at the application layer. Even if the third party does not know the contents of the data being circulated, it can clearly know when the communication was made and for what purpose. In comparison, a VPN creates a tunnel and all network activity goes through this tunnel. Since the tunnel is secured by a VPN, third parties won't know what's circulating.

Data channel encryption encrypts and decrypts packets sent over an OpenVPN tunnel.

You can configure it both server side and client side. However, the client and server must agree on supported and possible encryptions.

Support for different versions of data channel ciphers changes, but we strive to maintain backward compatibility.

OpenVPN Access Server 2.5 and later use AES-256-GCM by default.

Legacy clients that do not support AES-256-GCM use backup ciphers. Access server configurations created with version 2.5 or later use AES-256-CBC as a fallback cipher, while older configurations use BF-CBC as a fallback cipher.

AES-256 in CBC (Cipher Block Chaining) or GCM (Galois/Counter Mode) mode is considered secure and meets strict security requirements.

They have the same level of security, but newer versions of OpenVPN use the faster AES-GCM method to combine the encryption and authentication steps. Use SHA1 HMAC for authentication when using CBC mode.