How can a group of people figure out who is the oldest, without revealing any other information?
Revealing all the ages to a trusted third party is not allowed. Preferably I'm looking for solutions where nobody gets other information, not even a third party.
Preferably I'm looking for a solution which works for large (e.g. 64-bit or 1024-bit) age values as well. (Even though using the word age is not intuitive for such large numbers.)
I'm looking for a low-cost pencil-and-paper solution, or a solution in which each pair of people has a secure bidirectional communication channel (i.e. the digital equivalent of: anyone can write any message to a sheet of paper, fold it, and pass it to anyone else). I'm not looking for solutions which require building other kind of physical devices.
(Is there a book or web page describing such non-revealing algorithms?)
This question is not a duplicate of Non-revealing maximum , because this question doesn't ask for the maximum age value: it even explicitly forbids revealing the maximum age value, because that would be too much information shared. Having a solution to this question doesn't give us a solution to the other question. Having a solution to the other question doesn't give us a solution to this question.
The solution to Yao's Millionaires' Problem can be used to solve this question when the group size is 2. But in this question I'm interested in the answer for larger groups as well.