strongSwan - Definition from the Hotspot Shield Glossary

Strongswan is another IPsec implementation similar to Openswan and Libreswan but puts more emphasis on a strong level of authentication that uses public keys, or optional private keys. Strongswan is another derivative of the original FreeS/WAN implementation and is release under the GPL license.

This open-source IPsec VPN solution is available on Linux, Android, FreeBSD, Apple OS and Windows and claims to be fully operable on IPv6. Main features of the Strongswan project include strong authentication and encryption, potential for expansions in the future with a modular design, and a simple configuration. There is even a mobile app available for Android smartphones that can be downloaded in the Google Play store.