Split the file into N piece, put them in N different place. N/2 of the places is remember by you, the other N/2 places is remember by your partner.
In order to get the content, they will need to have all the pieces togather, which means bot of you will have to leak the information out.
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There is a perfect secrecy by using one time pad. Just that it is not feasible. Please pray to your local God for assistance.
http://en.wikipedia.org/wiki/One_time_pad |