Cadbury’s Caramilk chocolate is testing Canadians’ ability to keep a closely guarded secret in a new campaign that will name one consumer the caramel ‘protector.’

Today, Caramilk revealed that those who find the 10 hidden golden keys will be sent to the Cadbury Chocolate Factory in Toronto, where one person will be able to unlock the vault that holds an envelope containing the Caramilk secret (the famous ‘how they get the caramel into the bar’ secret). That person will receive $125,000 for having the right key, and another $125,000 if they return the envelope unopened after six months.

Cadbury will announce when each key is found through an intriguing use of OOH – the billboard at Yonge-Dundas Square in Toronto, a mural in Montreal, print ads in Metro daily newspapers, online and through a PR push, handled by Toronto’s Strategic Objectives. Cossette handled the media buy and Rocket XL developed the social media components, while The Hive was responsible for program creation, TV creative, print and OOH development (including storefront illumination), as well as website design and online advertising.

A teaser campaign launched on Facebook and Twitter in mid-May, asking Canadians what they thought the Caramilk Secret was really about, hiding the Keys to the Secret promotion ‘behind a virtual curtain,’ explains Mackenzie Davison, director, Every Day Chocolate, Cadbury.

More tantalizing details were released in early June with OOH, print and national TV ads in French and English Canada.

‘The Caramilk Key to the Secret program is an evolution of the campaign we’ve been talking about for over 40 years – it now engages consumers at a much deeper level,’ Davison tells MiC.