An apparatus for encrypting an input memory address to obtain an encrypted memory address comprises an input interface for receiving the input memory address being an address of a memory. Moreover, the apparatus comprises an encryption module for encrypting the input memory address depending on a cryptographic key to obtain the encrypted memory address. The encryption module is configured to encrypt the input memory address by applying a map mapping the input memory address to the encrypted memory address, wherein the encryption module is configured to apply the map by conducting a multiplication and a modulo operation using the cryptographic key and a divisor of the modulo operation, such that the map is bijective.