How do I use RSA authentication?

The RSA SecurID authentication mechanism consists of a "token"—a piece of hardware (e.g. a token or USB) or software (e.g. a "soft token" for a PDA or cell phone) assigned to a user that generates an authentication code every sixty seconds using a built-in clock and the card's factory-encoded random key (known as the "seed" and often provided as a *.asc file). The seed is different for each token, and is loaded into the corresponding RSA SecurID server (RSA Authentication Manager, formerly ACE/Server) as the tokens are purchased. The seed is typically 128 bits long. Some RSA SecurID deployments may use varied second rotations, such as 30-second increments.