( July 2009) ( Learn how and when to remove this template message) Unsourced material may be challenged and removed. Please help improve this article by adding citations to reliable sources. This section needs additional citations for verification. However, to make use of username/password authentications, OpenVPN depends on third-party modules. In version 2.0 username/password authentications can be enabled, both with or without certificates. Preshared secret key is the easiest, and certificate-based is the most robust and feature-rich. OpenVPN offers pre-shared keys, certificate-based, and username/password-based authentication. OpenVPN has several ways to authenticate peers with each other. Support for mbed TLS is available starting from version 2.3. It can also use hardware acceleration to get better encryption performance. It can also use the HMAC packet authentication feature to add an additional layer of security to the connection (referred to as an 'HMAC Firewall' by the creator). It lets OpenSSL do all the encryption and authentication work, allowing OpenVPN to use all the ciphers available in the OpenSSL package. OpenVPN uses the OpenSSL library to provide encryption of both the data and control channels. Additionally, commercial licenses are available. It was written by James Yonan and is free software, released under the terms of the GNU General Public License version 2 (GPLv2).

SoftEther VPN, a multi-protocol VPN server, also has an implementation of OpenVPN protocol.

For example, DD-WRT has the OpenVPN server function. OpenVPN has been ported and embedded to several systems. It is capable of traversing network address translators (NATs) and firewalls. It uses a custom security protocol that utilizes SSL/TLS for key exchange. It uses the OpenSSL encryption library extensively, as well as the TLS protocol, and contains many security and control features.

When used in a multiclient-server configuration, it allows the server to release an authentication certificate for every client, using signatures and certificate authority. OpenVPN allows peers to authenticate each other using pre-shared secret keys, certificates or username/ password. It implements both client and server applications. OpenVPN is a virtual private network (VPN) system that implements techniques to create secure point-to-point or site-to-site connections in routed or bridged configurations and remote access facilities.

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