A system is comprised of a user and a group, wherein the group is comprised of a group leader and a group of M members where M is equal to or greater than one. The group leader generates a group public key and a group leader “master” private key. The group leader creates a personalized watermarked or decryption key, also referred to as an individual private key, for each group member. The individual private key uniquely identifies each group member. The group leader distributes the individual private keys to each of the group members. Each group member receives from a user a message encrypted using the group public key. Each of the group members uses its individual private key to decrypt the encrypted message sent by the user to the group.