Methods, systems, and apparatuses, including computer storage media and hardware security modules, for performing batch cryptography on hardware security modules. A hardware security module can receive a request to perform one or more cryptographic operations. The request can include a batch data structure storing a plurality of data elements. The hardware security module can unbatch the plurality of data elements, perform one or more cryptographic operations on the plurality of data elements to generate a plurality of outputs, generate an output batch data structure storing the plurality of outputs, and transmit the output batch data structure in response to the request. The request and the batch data structure can be formed in accordance with a batch hardware security module application program interface (API) implemented by the hardware security module.