Method for accelerating bootstrapping in a cryptographic application

An accelerator for performing a bootstrapping operation in cryptographic application, the accelerator comprising

• a preprocessing block configured to receive one or more input ciphertexts to be bootstrapped and to iteratively process one or more accumulator variables in function of portions of the input ciphertexts, whereby each accumulator variable is linked to one input ciphertext and each iteration step is performed for each of the one or more accumulator variables in turn;
• an arithmetic unit configured to multiply, within each iteration, the processed accumulator variables with a bootstrapping key element belonging to a bootstrapping key comprising a plurality of bootstrapping key elements,
• wherein the accelerator further comprises a bootstrapping cache memory for storing the bootstrapping key element to be multiplied and adapted for loading into the bootstrapping cache memory a next bootstrapping key element of said plurality of bootstrapping key elements to be used in a next iteration of the bootstrapping operation, while performing the multiplying operation for each of the one or more accumulator variables in turn.