What is a pre-shared key or shared secret?
A pre-shared key (PSK) or shared secret is a string of text a VPN (virtual private network) or other service expects to get before it receives any other credentials (such as a username and password). Microsoft Windows calls this string the "pre-shared key for authentication", but in most operating systems it is known as a "shared secret".
When creating an IPsec VPN connection, the VPN server will not allow the authentication process to continue until the correct string of text is given. Unless the VPN server receives the shared secret, a username and password cannot be sent, and the connection will be refused. In a sense, a shared secret is sort of a password, albeit a weak one known by a large number of people.
Note: When connecting from off campus, SSL VPN is the replacement for IU's IPsec- and PPTP-based VPN services, and UITS recommends using it now if your campus supports it. PPTP is retired at IU Bloomington and IUPUI, and IPsec VPN service at those campuses will be retired by fall 2010.
Pre-shared keys are also used by a type of encryption sometimes used for home wireless networks called WPA-PSK and WPA2-PSK. This type of encryption is not used at Indiana University.
