A computer-implemented method comprising: for each of one or more campaigns: initializing, by a first computing system of a plurality of multi-party computation, MPC, systems and in collaboration with one or more second computing systems of the MPC systems, a feedback controller for the campaign in secret shares using a secure MPC process, wherein the feedback controller comprises a setpoint based on a target rate for the campaign; updating, by the first computing system, a first secret share of an output of the feedback controller based on an error parameter representing a difference between the setpoint and a measured rate for the campaign; and determining, by the first computing system and based at least on the first secret share of the output, a first secret share of a pacing selector parameter that defines whether the campaign satisfies a pacing eligibility condition for the campaign; receiving, by the first computing system, a digital component request; conducting, by the first computing system in collaboration with the one or more second computing systems, a given digital component selection process for the digital component request, wherein the digital component selection process selects a given digital component from a set of candidate digital components that each satisfy one or more eligibility conditions including being in an eligible campaign that satisfies the pacing eligibility condition; and sending, by the first computing system and to the client device, a first secret share of a selection result that identifies the given digital component; and wherein generating the first secret share of the selection result comprises: generating an order of the plurality of digital components based on a magnitude of each selection value; determining, based on the order of the digital components and the overall candidate parameter for each digital component, a first secret share of an accumulated value for each selection value; determining, for each digital component, a first secret share of a winner parameter based on (i) the overall candidate parameter for the selection value and (ii) a result of an equality test that indicates whether the accumulated value for the selection value is a particular specified value; and determining, as the first secret share of the selection result, a first secret share of a sum of, for each selection value, a product of the winner parameter for the selection value and a digital component information element for the selection value. for each of one or more campaigns: initializing, by a first computing system of a plurality of multi-party computation, MPC, systems and in collaboration with one or more second computing systems of the MPC systems, a feedback controller for the campaign in secret shares using a secure MPC process, wherein the feedback controller comprises a setpoint based on a target rate for the campaign; updating, by the first computing system, a first secret share of an output of the feedback controller based on an error parameter representing a difference between the setpoint and a measured rate for the campaign; and determining, by the first computing system and based at least on the first secret share of the output, a first secret share of a pacing selector parameter that defines whether the campaign satisfies a pacing eligibility condition for the campaign; initializing, by a first computing system of a plurality of multi-party computation, MPC, systems and in collaboration with one or more second computing systems of the MPC systems, a feedback controller for the campaign in secret shares using a secure MPC process, wherein the feedback controller comprises a setpoint based on a target rate for the campaign; updating, by the first computing system, a first secret share of an output of the feedback controller based on an error parameter representing a difference between the setpoint and a measured rate for the campaign; and determining, by the first computing system and based at least on the first secret share of the output, a first secret share of a pacing selector parameter that defines whether the campaign satisfies a pacing eligibility condition for the campaign; receiving, by the first computing system, a digital component request; conducting, by the first computing system in collaboration with the one or more second computing systems, a given digital component selection process for the digital component request, wherein the digital component selection process selects a given digital component from a set of candidate digital components that each satisfy one or more eligibility conditions including being in an eligible campaign that satisfies the pacing eligibility condition; and generating an order of the plurality of digital components based on a magnitude of each selection value; determining, based on the order of the digital components and the overall candidate parameter for each digital component, a first secret share of an accumulated value for each selection value; determining, for each digital component, a first secret share of a winner parameter based on (i) the overall candidate parameter for the selection value and (ii) a result of an equality test that indicates whether the accumulated value for the selection value is a particular specified value; and determining, as the first secret share of the selection result, a first secret share of a sum of, for each selection value, a product of the winner parameter for the selection value and a digital component information element for the selection value.