I'm not following your equations (you seem to have C=2^y and 2^x at the same time(?)). Generally the way 3 party works is just like 2 party except you do every operation with both other parties, and the resulting secret is 2^x^y^z.
I'm not following your equations (you seem to have C=2^y and 2^x at the same time(?)). Generally the way 3 party works is just like 2 party except you do every operation with both other parties, and the resulting secret is 2^x^y^z.