receiving, from a client device and by a first computing system of a plurality of multi-party computation (MPC) systems, a digital component request comprising first secret shares of data identifying user groups that include a user of the client device as a member and a set of contextual signals;

transmitting, by the first computing system, a contextual digital component request to a content platform;

receiving, by the first computing system and from the content platform, selection data for a plurality of digital components, wherein the selection data comprises first vector data defining a contextual-based vector of values selected based at least in part on the set of contextual signals;

obtaining, by the first computing system and for each of the plurality of digital components, second vector data defining a user group-based vector of values selected based at least in part on a respective user group corresponding to the digital component;

determining, by the first computing system, a selection value for each digital component based on the first vector data and the second vector data;

determining, for each digital component, a candidate parameter that indicates whether the respective user group identifier corresponding to the digital component matches a user group that includes the user as a member;

generating, based on the selection values and the candidate parameters, a first secret share of a selection result that identifies, from a plurality of candidate digital components, a given digital component having a highest selection value, wherein each candidate digital component is a digital component for which the candidate parameter for the selection value corresponding to the digital component indicates that the respective user group identifier corresponding to the selection value matches a user group that includes the user as a member; and

transmitting, to the client device, the first secret share of a selection result identifying the given digital component.