You don't need a server to make something decryptable by 3 people. Just distribute to each person 1/3 of the key. If you want to allow any 3 of n-people to dec

You don't need a server to make something decryptable by 3 people. Just distribute to each person 1/3 of the key. If you want to allow any 3 of n-people to decrypt the archives, produce one archive for each combination of possible passwords among the n-people. To make things simple assign each person a letter and name the archives with 3-letter names indicating whose password is necessary and what order to enter the passwords.