VeriSign has released a set of tools which allows firms to deploy one-time password systems.

The one-time passwords serve as an extra layer of protection which can be used in combination with a username and password to verify users.

The password is generated on demand or at a regular interval, and displayed on a small device such as the PayPal key fob.

Site owners will be allowed to access a set of APIs, and are provided with one year of free access to the VeriSign Identity Protection (VIP) system.

VIP allows a site to contact a central server for the one-time password. After logging in, the credential can then be used on other sites that subscribe to the VIP service.

VeriSign also said that companies which sign a two-year contract with the service will receive their first 5,000 security tokens for free, a move which the company hopes will boost participation in the programme.

"We are making an investment to ensure that the service is relevant," said Kerry Loftus, vice president of consumer authentication at VeriSign.

One of the early partners for the service will be AOL, which plans to use VIP to supplement its OpenID initiative.