An apparatus and method for managing the distribution and expansion of public keys held by a group or array of systems in white lists. The addition of a new system to the array entails a manual input to authorize the introduction of the new system to one trusted system in the array. After the introduction the new system is trusted by the one member and the white list of the one member is loaded into the white list of the new system. The new system then requests joining each of the other systems in the array. For each system in the array asked by the new system, the systems in the array ask if any other systems in the array already trust the new member. In response, a system of the array that trusts the new system responds by sending its white list (containing the public key of the new system) to the requesting system. Eventually the public key of the new system is in the white lists of all the systems in the array. In practice this trusts expansion occurs in the background with respect to running applications.