WireGuard: fast, modern, secure VPN tunnel

WireGuard® is an extremely simple yet fast and modern VPN that utilizes state-of-the-art cryptography. It aims to be faster, simpler, leaner, and more useful than IPsec, while avoiding the massive headache. It intends to be considerably more performant than OpenVPN. WireGuard is designed as a general purpose VPN for running on embedded interfaces and super computers alike, fit for many different circumstances. Initially released for the Linux kernel, it is now cross-platform (Windows, macOS, BSD, iOS, Android) and widely deployable. It is currently under heavy development, but already it might be regarded as the most secure, easiest to use, and simplest VPN solution in the industry.
If you'd like a general conceptual overview of what WireGuard is about, read onward here. You then may progress to installation and reading the quickstart instructions on how to use it.
If you're interested in the internal inner workings, you might be interested in the brief summary of the protocol, or go more in depth by reading the technical whitepaper, which goes into more detail on the protocol, cryptography, and fundamentals. If you intend to implement WireGuard for a new platform, please read the cross-platform notes.
WireGuard securely encapsulates IP packets over UDP. You add a WireGuard interface, configure it with your private key and your peers' public keys, and then you send packets across it. All issues of key distribution and pushed configurations are out of scope of WireGuard; these are issues much better left for other layers, lest we end up with the bloat of IKE or OpenVPN. In contrast, it more mimics the model of SSH and Mosh; both parties have each other's public keys, and then they're simply able to begin exchanging packets through the interface.
WireGuard works by adding a network interface (or multiple), like eth0 or wlan0, called wg0 (or wg1, wg2, wg3, etc). This network interface can then be configured normally using ifconfig(8) or ip-address(8), with routes for it added and removed using route(8) or ip-route(8), and so on with all the ordinary networking utilities. The specific WireGuard aspects of the interface are configured using the wg(8) tool. This interface acts as a tunnel interface.
WireGuard associates tunnel IP addresses with public keys and remote endpoints. When the interface sends a packet to a peer, it does the following:
When the interface receives a packet, this happens:
Behind the scenes there is much happening to provide proper privacy, authenticity, and perfect forward secrecy, using state-of-the-art cryptography.
At the heart of WireGuard is a concept called Cryptokey Routing, which works by associating public keys with a list of tunnel IP addresses that are allowed inside the tunnel. Each network interface has a private key and a list of peers. Each peer has a public key. Public keys are short and simple, and are used by peers to authenticate each other. They can be passed around for use in configuration files by any out-of-band method, similar to how one might send their SSH public key to a friend for access to a shell server.
For example, a server computer might have this configuration:
And a client computer might have this simpler configuration:
In the server configuration, each peer (a client) will be able to send packets to the network interface with a source IP matching his corresponding list of allowed IPs. For example, when a packet is received by the server from peer gN65BkIK..., after being decrypted and authenticated, if its source IP is 10.10.10.230, then it's allowed onto the interface; otherwise it's dropped.
In the server configuration, when the network interface wants to send a packet to a peer (a client), it looks at that packet's destination IP and compares it to each peer's list of allowed IPs to see which peer to send it to. For example, if the network interface is asked to send a packet with a destination IP of 10.10.10.230, it will encrypt it using the public key of peer gN65BkIK..., and then send it to that peer's most recent Internet endpoint.
In the client configuration, its single peer (the server) will be able to send packets to the network interface with any source IP (since 0.0.0.0/0 is a wildcard). For example, when a packet is received from peer HIgo9xNz..., if it decrypts and authenticates correctly, with any source IP, then it's allowed onto the interface; otherwise it's dropped.
In the client configuration, when the network interface wants to send a packet to its single peer (the server), it will encrypt packets for the single peer with any destination IP address (since 0.0.0.0/0 is a wildcard). For example, if the network interface is asked to send a packet with any destination IP, it will encrypt it using the public key of the single peer HIgo9xNz..., and then send it to the single peer's most recent Internet endpoint.
In other words, when sending packets, the list of allowed IPs behaves as a sort of routing table, and when receiving packets, the list of allowed IPs behaves as a sort of access control list.
This is what we call a Cryptokey Routing Table: the simple association of public keys and allowed IPs.
Any combination of IPv4 and IPv6 can be used, for any of the fields. WireGuard is fully capable of encapsulating one inside the other if necessary.
Because all packets sent on the WireGuard interface are encrypted and authenticated, and because there is such a tight coupling between the identity of a peer and the allowed IP address of a peer, system administrators do not need complicated firewall extensions, such as in the case of IPsec, but rather they can simply match on "is it from this IP? on this interface?", and be assured that it is a secure and authentic packet. This greatly simplifies network management and access control, and provides a great deal more assurance that your iptables rules are actually doing what you intended for them to do.
The client configuration contains an initial endpoint of its single peer (the