There is provided an example memory system comprising a plurality of memory modules, each memory module comprising a persistent memory to store root key information and encrypted primary data; a volatile memory to store a working key for encrypting data, the encrypted primary data stored in the persistent memory being encrypted using the working key; and a control unit to provide load and store access to the primary data. The memory system further comprises a working key recovery mechanism to retrieve first root key information from a first module and second root key information from a second module; and compute the working key for a given module based on the retrieved first root key information and the retrieved second root key information.