Weblog tools vendor Six Apart is in the latter stages of plans to roll out an open online authentication system to thwart comment spammers.

Not much is known about the new TypeKey service but San Mateo, Calif.-based Six Apart promises it will be a free system that provides a central identity that anyone can use to log in and post comments on blogs and other Web sites.

It is the company's response to the "comment spam" problem being encountered by Web publishers who enable a feature to allow readers to reply to news and stories.

Spammers have taken a liking to blogs, adding hyperlinks and innocuous messages among legitimate comments as part of a scheme to manipulate results on search pages.

Because some search engines like Google return search results based on the number of pages that link to a particular site, spammers are bombarding blogs with fake comments and links to sites hawking pornography, medical and herbal products.

While many have sought temporary respite from Blacklist plug-ins, Six Apart believes TypeKey could shift the power to authenticate comments back into the hands of publishers.

"TypeKey helps ensure that people who comment on a site have a verified identity, keeping conversations on track and helping to prevent abusive or offensive content (comment spam) from being posted. Sites that enable TypeKey have better accountability for the content that's being published," the company said in preview material released this week.

A blogger or Web publisher using TypeKey gets complete control over who can post comments, while limiting the process to a single sign-in for readers. "A lower barrier to comment registration means your commenters won't encounter any barriers while expressing themselves. And all weblog comments and other data still live on your server."

With TypeKey, publishers can also manage comments to delete spam before it appears on Web sites.

Six Apart plans to ship the first version of TypeKey with its upgraded Movable Type 3.0 product later this spring but the service would also be available for competing blog vendors. The company said it would provide documentation on how to integrate the authentication service into third-party commercial applications.

Six Apart, founded by the Ben and Mena Trott in 2002, is backed by Tokyo, Japan-based venture capital firm Neoteny. Former PayPal executive Reid Hoffman, who now runs the LinkedIn social software platform, is also an investor.