# Unanimity for three (or more) players

The article Cryptographic Protocols with Everyday Objects by James Heather, Steve Schneider, and Vanessa Teague describes the following unanimity protocol for three players:

Three players want to determine whether they all agree on the point at issue; if they do not all agree, then they will not discover who stands alone against the other two. This is useful in situations where eventual consensus is required, but there is a danger that voters might be unduly influenced by knowledge of the other votes.

Q: The given solution uses playing cards. What is the most natural cryptographic solution of this problem? (Hopefully it will work for more players.)

The secure two-party computation of logical AND from the same article was discussed at Is there a cryptographic solution for this “dating protocol”?.

• It may be helpful, to realize that this is a secure multi-party computation of a three-input AND. – SEJPM Mar 3 '18 at 10:28
• @SEJPM It is not exactly AND. It is $(abc)OR(\bar a\bar b\bar c).$ – Alexey Ustinov Mar 3 '18 at 10:36