IPsec (IP for “Inter­net Pro­to­col” and sec for “secure”) is a group of pro­to­cols to ensure the integri­ty, con­fi­den­tial­i­ty and authen­ti­ca­tion of data com­mu­ni­ca­tions over an IP network.

IPsec is com­mon­ly used as a base for VPNs (Vir­tu­al Pri­vate Net­works), encrypt­ing the IP pack­ets and authen­ti­cat­ing the source where the pack­ets come from.

Ter­mi­nal Access Con­troller Access-Con­trol Sys­tem Plus (TACACS+) is a pro­to­col devel­oped by Cis­co to han­dle authen­ti­ca­tion, autho­riza­tion, and account­ing (AAA) ser­vices and was released as an open stan­dard begin­ning in 1993.

It is an exten­sion of its pre­de­ces­sor TACACS, encrypt­ing the full con­tent of each pack­et and pro­vides gran­u­lar con­trol (com­mand by com­mand autho­riza­tion) whilst oper­at­ing over TCP.

Open­VPN is a vir­tu­al pri­vate net­work (VPN) pro­to­col and soft­ware for both client and serv­er applications.

It imple­ments tech­niques to cre­ate secure point-to-point or site-to-site con­nec­tions in rout­ed or bridged con­fig­u­ra­tions and remote access facil­i­ties enabling peer authen­ti­ca­tion using pre-shared secret keys, cer­tifi­cates or usernames/passwords.

Pub­lic key infra­struc­ture (PKI) refers to a range of tech­nolo­gies for authen­ti­cat­ing users and devices in order to secure the dig­i­tal trans­fer of infor­ma­tion for a range of net­work activ­i­ties such as e‑commerce, inter­net bank­ing and con­fi­den­tial email.

It includes a set of roles, poli­cies, hard­ware, soft­ware and pro­ce­dures need­ed to cre­ate, man­age, dis­trib­ute, use, store and revoke dig­i­tal cer­tifi­cates and man­age pub­lic-key encryption.