Google today announced it would again host its Pwnium hacking contest at a March security conference, but boosted the maximum amount it will pay to $3.14 million and changed the target to its browser-based operating system, Chrome OS.

Dubbed Pwnium 3, the challenge will pit researchers against its still-struggling-for-relevance Chrome OS, rewarding those who can hack the operating system with individual prizes of $110,000 and $150,000.

Google capped the total up for grabs at $3.14159 million, giving multiple researchers a chance at prize money. The "3.14159" comes from the first six digits of the value of Pi.

Each hacker able to compromise Chrome OS or the browser that is its foundation -- Chrome -- from an exploit-serving website will receive $110,000 said Chris Evans, an engineer with the Chrome security team, in a Monday entry on the Chromium project's blog.

Researchers who manage to accomplish what Evans called a "compromise with device persistence," meaning that the hijack survives a reboot of the Chrome OS-powered notebook, will receive the larger award of $150,000.

"We believe these larger rewards reflect the additional challenge involved with tackling the security defenses of Chrome OS, compared to traditional operating systems," said Evans.

Pwnium 3 will take place March 7 at CanSecWest, the Vancouver, British Columbia, security conference where Google will also partner with HP TippingPoint's Zero Day Initiative (ZDI) bug bounty program to host Pwn2Own. That contest, with $560,000 in total cash prizes, will focus on Web browsers, including Chrome, Microsoft's Internet Explorer (IE) and Mozilla's Firefox, as well as plug-ins from Adobe and Oracle.

The contest cooperation at CanSecWest will be quite different this year than in 2012, when Pwn2Own and Pwnium were rivals. Google inaugurated Pwnium then after it withdrew its financial support from Pwn2Own after it and HP couldn't agree on the rules -- specifically, whether researchers would be required to divulge full exploits and hand over all the vulnerabilities they used to hack a browser.

"This year, we've teamed up with ZDI by working together on the Pwn2Own rules and by underwriting a portion of the winnings for all targets," said Evans about the new understanding between Google and HP TippingPoint. "The new rules are designed to enable a contest that significantly improves Internet security for everyone. At the same time, the best researchers in the industry get to showcase their skills and take home some generous rewards."

Both Pwn2Own and Pwnium will require winners to provide functional exploit code and details on all the vulnerabilities put into play.

Pwnium 3's $3.14 million cap is more than three times the $1 million Google said it would pay if necessary in 2012, and more than 50% above the $2 million it staked at a second challenge that took place in Kuala Lumpur, Malaysia, last October.

But if past practice holds true again this year, Google won't write checks totaling anywhere near $3 million. At the first Pwnium of March 2012, the search giant paid out $120,000 to two researchers for exploiting Chrome; the Malaysian edition's single award was a $60,000 payoff to "Pinkie Pie," one of the two hackers who took home the same amount seven months earlier.

Chrome OS has never been a contest target before, although Pwn2Own offered a Chrome OS notebook as one of four laptop prizes in 2011.

Although Chrome OS continues to struggle to gain share -- metrics company Net Applications, one of the most-cited market scorekeepers, hasn't even bothered to measure the operating system's usage -- but several major computer makers have recently gotten behind the open-source operating system. Earlier this month, Lenovo joined Acer and Samsung when it introduced a $429 ThinkPad laptop that's scheduled to ship in February.

Acer's C7 "Chromebook" -- a term often applied to notebooks powered by Chrome OS -- costs just $199, while Samsung's line starts at $249.

Google has not yet posted the official rules for Pwnium 3, but they will probably appear on the Chromium Security page.

Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer, on Google+ or subscribe to Gregg's RSS feed . His email address is gkeizer@computerworld.com.

See more by Gregg Keizer on Computerworld.com.