Time synchronous authentication is an authentication method that relies on a timing value to authenticate the token bearer.

All token authentication applications work with an input value from some source. The input value is encrypted according to some algorithm, using a key. The encrypted value is displayed as a one-time password that the token bearer types into a computer or other device to gain access.

In time synchronous authentication, both the token, often called a hardware authenticator, and the server keep track of clock time. The clock time is the input value for the encryption process and it’s encrypted with the seed record. The resulting value is entered as a one-time password at the login prompt. The server does the same computation in order to authenticate the token bearer.