Marketers and advertisers want to reach you with ads and messages across all your devices, so there’s a big emphasis these days on cross-device targeting.

But the challenge is to make sure it’s really you on the various devices, especially since you’re anonymous to most marketers and advertisers. To boost their cross-device chops, open ad management platform Sizmek is today announcing a global partnership with cross-device identity management vendor Screen6.

The Austin-based Sizmek said it conducted a thorough review of potential cross-device identity partners before settling on Screen6. It said Screen6, headquartered in Amsterdam, was the only one that covers such developing markets as Latin America and all of Asia, which are growth regions for mobile adoption.

The move reflects jockeying on the part of ad and marketing platforms as they compete to assemble the pieces necessary to more reliably track and target users across devices.

A key driver is the increasing power of Facebook and Google, which have huge numbers of registered users who are very reliably identified as they log in from different devices.

One example of the realignment going on is today’s announcement by Publishers Clearing House’s (PCH) adtech platform Liquid that it has purchased CRM provider CommandIQ.

The clear intention with the acquisition is to create a new generation of CRM for client companies, which can target their own customers when logged in on various devices. They can then “lookalike” match those same customer types on PCH’s enormous subscriber base to target new customers across devices. PCH claims to have direct business relationships (that is, identified customers) with 70 percent of all U.S. households.

But, like most ad and marketing platforms, Sizmek does not have Facebook’s, Google’s, or PCH’s large subscriber base of identified users. Instead, it is creating anonymous cross-device profiles of users based on reactions to its ads, and other signals like mobile device IDs, IP address locations, behavioral patterns, and other probabilities that, together, can be used to infer that this is the same person visiting a given web site from different devices.

Nevertheless, Sizmek has enormous reach for its ads, operating in over 70 countries, serving over 40,000 advertisers and agencies, and integrated with more than 100 partners in attribution, data management, and other areas.

John Tegner, product marketing manager, told me that the first focus of the partnership is to implement cross-device attribution by the end of this year, followed by cross-device targeting sometime next year.

The attribution phase, he said, will determine user behavior patterns so that a Universal User ID can be created to infer a single person’s identity across devices, with about 80 percent accuracy.

Sizmek will provide the data, he said, while Screen6 offers the technology. No third-party data — that is, anonymous behavioral and other data obtained from other companies — will be used.