A memory system , comprising: a first electronic device comprising a processor ; a second electronic device being external to the first electronic device and comprising a memory , wherein the memory stores a memory image over at least a part of a data set stored on the memory ; and wherein a secure memory of the first electronic device stores a hash value related to the memory image ; wherein the first electronic device and the second electronic device are coupled such that the processor has at least partial control over the second electronic device ; and wherein the processor is configured to, when updating the data set and the memory image stored on the memory of the second electronic device , update the hash value related to the memory image using an incremental hashing operation so that only parts of the memory image are processed that have changed; wherein the memory of the second electronic device stores a table being indicative for information and versions of the parts of the memory image ; wherein the hash value is calculated from the table such that said hash value allows to verify the integrity of said table , and wherein the processor is further configured to, when updating the data set and the memory image , update the hash value over the table using the incremental hashing operation so that only parts of the table are processed that have changed; wherein the memory image is divided into a plurality of pages ; wherein the table is a page version table that comprises a version number , in particular also a signature, of each page , wherein said version number is employed to be compared with a corresponding version number comprised in each page ; and wherein the processor is further configured to, when the contents of a page change, increment the version number for said page in the page version table and increment a version number of the page version table. a first electronic device comprising a processor ; a second electronic device being external to the first electronic device and comprising a memory , wherein the memory stores a memory image over at least a part of a data set stored on the memory ; and wherein a secure memory of the first electronic device stores a hash value related to the memory image ; wherein the first electronic device and the second electronic device are coupled such that the processor has at least partial control over the second electronic device ; and wherein the processor is configured to, when updating the data set and the memory image stored on the memory of the second electronic device , update the hash value related to the memory image using an incremental hashing operation so that only parts of the memory image are processed that have changed; wherein the memory of the second electronic device stores a table being indicative for information and versions of the parts of the memory image ; wherein the hash value is calculated from the table such that said hash value allows to verify the integrity of said table , and wherein the processor is further configured to, when updating the data set and the memory image , update the hash value over the table using the incremental hashing operation so that only parts of the table are processed that have changed; wherein the memory image is divided into a plurality of pages ; wherein the table is a page version table that comprises a version number , in particular also a signature, of each page , wherein said version number is employed to be compared with a corresponding version number comprised in each page ; and wherein the processor is further configured to, when the contents of a page change, increment the version number for said page in the page version table and increment a version number of the page version table. <EOS>