Homomorphic evaluation including key switching, modulus switching, and dynamic noise management

A computer program product comprising a computer readable storage device having program code embodied therewith, the program code readable/executable by a computer to perform

• a method, comprising:
• Performing, by a computing device, homomorphic evaluation of a function on one or more input ciphertexts, where the one or more input ciphertexts were encrypted using a public key of an encryption scheme that also comprises a plurality of secret keys and a plurality of moduli, where the moduli are integers, and where performing the homomorphic evaluation of the function comprises performing one or more operations on the input ciphertexts, where the function comprises one or multiple operations comprising one of more of addition, multiplication, and automorphism;
• Performing a key-switching transformation on selected ones of the one or more input ciphertexts, where performing a key-switching transformation on a selected ciphertext comprises converting a first version of the selected ciphertext with respect to a first of the plurality of secret keys and a first modulus to a second version of the selected ciphertext with respect to a second of the plurality of secret keys and a second secret modulus, where the second modulus is an integer factor p times the first modulus, where p>1,
• Where each of the key switching transformations is performed prior to or after the one or more operations are evaluated;
• and outputting one or more results of the one or more operations.