Premier users of Google Apps users now have a more secure way to log on to the online groupware service, after Arcot Systems announced that it was making its A-OK On-Demand authentication service available to the service.

The tie-up applies only to Google Apps Premier Edition.

Typically Google Apps users enter a username and password to get access to the web-based mail, calendar and groupware software, but with the A-OK product they also use an encrypted file that is stored on their computer to add a second factor of authentication.

As with online banking products, if the user tries to log on from a different computer, A-OK will ask predetermined questions, such as "What high school did you attend", before granting the user access to Google Apps.

This is the first time that Google has partnered with someone to provide two-factor authentication for Google Apps, according to Eran Feigenbaum, senior security manager with Google Enterprise.

"Google has the tools to show you how to pick a good password," he said, "but to the companies that are concerned about users losing their passwords, I think the Arcot two-factor authentication product is perfect."

Since launching more than a year ago, Google Apps has added more than 500,000 customers, but some of them are looking for a higher level of security when it comes to signing on to the service, Feigenbaum said.

Feigenbaum hopes that Arcot's two-factor product will make Google Apps more appealing in markets where this kind of strong authentication is a common requirement, such as the financial services and defense industries.

The A-OK On-Demand service is available now, for US$1 (50p) per user per year.