1. A system, comprising: one or more processors; memory including instructions that, when executed by the one or more processors, cause the system to: receive a set of web service application programming interface calls that specifies a function and an execution instance for evaluating the function; configure the execution instance to evaluate the function; provide a cryptographically verifiable attestation of the function; receive, from each party of a plurality of parties, a respective input value, thereby resulting in a plurality of input values for the function; cause the execution instance to evaluate the function based at least in part on the plurality of input values, thereby generating an output of the function; and provide the output of the function without revealing any of the plurality of input values for the function.