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.